Effects of dinotefuran and humic acid on cadmium migration and transformation in sediments

Effects of dinotefuran and humic acid on cadmium migration and transformation in sediments | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effects of dinotefuran and humic acid on cadmium migration and transformation in sediments Haibo Wang, Mengyang Bian, Shuhua Yao, Shifeng Li This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4127483/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The heavy application of dinotefuran (DNT) pesticide in agricultural production and the humic acid (HA) ubiquitous in the aqueous systems have burdened the environment as a new pollutant. The chemical fraction and mobility of cadmium (Cd) in sediments of urban river environments in which DNT and HA coexist are poorly understood. In this study, sequential extraction, ultraviolet-visible spectroscopy (UV-vis), fluorescence excitation-emission matrix (EEM), fourier transform infrared spectrometer (FTIR) techniques, and the Stern-Volmer equationwere integrated to identify the effects of DNT, pH, concentration and molecular weight (Mw) fractions of HA on the content and chemical fraction of Cd in sediments. The DNT dosage strongly affected the Fe–Mn oxide-associated Cd chemical fraction in sediments. HA facilitated migration of Cd from sediments to water. Cd release from sediments was also promoted by a lower pH of 5–6 compared to pH 8–9. Increasing concentrations of higher molecular weight HAs of >100 kDa, 30–100 kDa, and 30–10 kDa reduced total Cd, exchangeable/acid soluble fraction, and reducible fraction content in sediments, while 1–10 kDa and <1 kDa HA did not significantly influence Cd chemical fraction or content. The present study provides new insights into the environmental risks and partitioning of Cd in sediments under co-exposure to DNT and HA. Humic acid Dinotefuran Cadmium Chemical fraction Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 Figure 8 Figure 10 1. Introduction Cadmium (Cd) is a highly mobile and toxic element that has substantial deleterious effects on aquatic ecosystems and human health, raising serious public concern in many parts of the world (Wang et al., 2016; Jalali et al., 2021; Wang et al., 2023; Zarei et al., 2023). Cd content in aquatic ecosystems have become elevated due to increasing discharges of urban, agricultural, and industrial wastewater (Tian et al., 2020). After Cd enters the aquatic environment, it is mainly sequestered in the sediment through various adsorption and absorption processes (Rajeshkumar et al., 2018; Jaskuła and Sojka, 2022), causing Cd to become enriched in sediments. Changes in aquatic parameters such as dissolved oxygen (Liu et al., 2022), dissolved organic matter (Wang et al., 2010), pesticides (Wang et al., 2016), salinity (Jia et al., 2021), pH, and redox potential (Wang et al., 2023) can release Cd from sediments, leading to secondary pollution of overlying waters. The extensive use of pesticides has led to widespread contamination of aquatic ecosystems (Mitchell et al., 2017), neonicotinoid pesticides are currently the most widely used class of pesticides in the world (Gutiérrez-Sánchez et al., 2017). Neonicotinoid pesticides are ubiquitous in aquatic systems at concentrations that exceed the regulatory guidelines of the USA and Canada, as well as ecotoxicological thresholds for many beneficial organisms (Wolfram et al., 2018; Borsuah et al., 2020). Neonicotinoid pesticides can compete with Cd for the same binding sites on sediment surface through electrostatic interactions and hydrogen bonding (Wang et al., 2016). In addition, neonicotinoid pesticides can directly form new compounds with Cd, which are then adsorbed onto sediments (Wang et al., 2016; Singh et al., 2017). Moreover, neonicotinoid pesticides can release H + , altering sediment pH, which may indirectly accelerate or inhibit the release of Cd from the sediments (Yu et al., 2019). Humic acid (HA) is the main component of dissolved organic matter and is ubiquitous in aquatic environments (Wang et al., 2021; Liu et al., 2023). HA is one of the most important participants in the global carbon cycle (Schmidt et al., 2011). HA has a porous and loose spongy structure with a large surface area and many reactive sites (Campitelli et al., 2006). It contains various reactive functional groups, such as carbonyl, carboxyl, and phenolic hydroxyl groups, as well as peptide and sugar fragments with polyelectrolyte/polybiszeolite properties (Samios et al., 2007; Xu et al., 2022). These reactive groups affect partitioning and transformation of Cd and neonicotinoid pesticides via adsorption, complexation, and redox processes (Barriuso et al., 1992; Helal et al., 2006). Interactions between HA and neonicotinoids have received public and regulatory attention due to their effects on the environmental behavior of pollutants in aquatic ecosystems. Pan et al. (2021) reported neonicotinoid pesticides (dinotefuran, clothianidin, and nitenpyram) could quench the endogenous fluorescence of HA through a static quenching process dominated by hydrogen bonds and van der Waals forces. Ćwieląg-Piasecka et al. (2018) found that HA exhibits high affinity for polar, ionic pesticides with high water solubility, which can be adsorbed via specific interactions with HA functional groups. Liu et al. (2018) reported that HA contains a variety of functional groups that act as adsorption sites, regulating pesticide adsorption onto the soil surface. Focusing only on the toxicity of individual constituents introduces uncertainty in ecological risk assessment; it is important to consider that interactions between HA and neonicotinoids may alter their individual behavior. The sediment-water system is very sensitive; both HA and neonicotinoids may greatly influence the mobility and transport of Cd from the sediment into the water, posing additive or synergistic ecological and environmental risks. DNT is a third-generation neonicotinoid pesticide with relatively high solubility and persistence, with commensurately greater risks to aquatic ecosystems (Lu et al., 2023). No systematic studies have been conducted evaluating the release of Cd from the sediment in water-sediment systems under co-exposure to DNT and HA. The objectives of the current study were to (1) systematically study the effects of pH, dissolved organic carbon (DOC), the molecular weight (Mw) of HA, and dose of DNT on release of Cd from the sediment, (2) evaluate changes in the chemical fraction of Cd in sediments under DNT and HA co-exposure from simple to complex systems, and (3) elucidate the mechanisms and controlling factors of Cd chemical fraction changes with interactions between DNT and HA. This study provides theoretical information and support for health risk assessment of co-exposure to these chemicals in aquatic environments. 2. Materials and methods 2.1. Reagents DNT (>98%) and HA were purchased from Mylin Technology Co., LTD. (Shanghai, China) and Sigma Corporation (Shanghai, China), respectively. Cadmium standard solution was purchased from the National Analysis and Testing Center for Metal and Electronic Materials (Shanghai, China). All other chemicals were analytically pure and purchased from Sinopharm Group Chemical Reagent Co., LTD. (Shanghai, China). 2.2 Sediments Sediment samples were collected at Dapan in the Xihe River Basin, Shenyang City, Liaoning Province (41° 66' N, 123° 11' E). Surface sediments (a depth of 0–20 cm) were collected using a plastic grab sampler and packed into polyethylene sample bags. The samples were air-dried, ground using an agate mortar, sieved with a 200-mesh nylon sieve, and stored at -20℃ for subsequent experiments. Ten grams of sediment were placed in a beaker containing 25 mL of CaCl 2 solution (0.01 M). The beaker was sealed with plastic wrap and shaken at room temperature for 30 min. 2.3 Cadmium analysis Sediments (0.10 g) were digested in 3 mL of HNO 3 -HF (molar ratio 1:2) acid solution at 190°C for 24 h. After cooling, the solution was heated with an electric heating plate (200°C) until no liquid remained. Then, 5 mL of 68 wt.% HNO 3 solution was added and the solution was held at 130°C for 3 h. Finally, the digested sample was filtered through a 0.45μm microporous membrane and diluted in a 25 mL volumetric flask. An atomic absorption spectrophotometer (AA-6880, Shimadzu, Japan) was used to measure the Cd content of the final samples. The total content of Cd in the original sediments was 5.90 mg·kg -1 . 2.4 Chemical fraction of Cadmium The European Community Bureau of Reference (BCR) sequential extraction method (Pueyo et al. 2001) was employed to study the chemical fractions of Cd in the sediments (Table 1; Wang et al., 2022). Please insert 2.5Molecular weight of the humic acid HA (0.20 g) was dissolved in 200 mL of KOH (0.02 M), then filtered through a 0.45-mm filtration membrane (Liu & Cai, 2010). The above solution (defined as pristine-HA, UF0) was divided into Mw fractions of >100 kDa (UF1), 30–100 kDa (UF2), 10–30 kDa (UF3), 1–10 kDa (UF4), and <1 kDa (UF5) using an ultrafiltration Amicon stirred cell (UFSC20001; Beverley, MA, USA) (Ren et al., 2017) technique with the nominal ultrafiltration membranes of 100, 30, 10 and 1 kDa (regenerated cellulose; diameter 63.50 mm; Millipore Corporation, Billerica, MA, USA). The ultrafiltration separation was performed from 100 kDa to 1 kDa; the ratio of the bulk volume of the HA sample before ultrafiltration and the residual volume of HA on the membrane after ultrafiltration was 6:1. The concentration unit used for the HA fractions was the DOC concentration (TOC-VCSN; Shimadzu, JPN). 2.6 Characterization UV-vis absorption spectra of HAs were collected using a P4 spectrophotometer (Shanghai, China). FTIR was performed in the range of 4000 to 400 cm −1 . The FTIR spectra of HAs with and without DNT, and for DNT were measured on a Thermo Fisher Nicolet 6700 FTIR spectrometer (MA, USA) using potassium bromide pellets. The HA solutions containing different doses of DNT were scanned with a fluorescence spectrophotometer (PE-LS55, USA) in a 1cm quartz colorimeter. Both the excitation and emission slit widths were set to 10nm and the scanning speed was 800 nm/min. The excitation wavelength was set at 288nm and the emission wavelength was set at 250–600nm. Excitation emission matrix (EEM) spectra of HAs were scanned using an F-2700 fluorescence spectrometer (Joint-stock, Japan). For all of the above fluorescence measurements, the excitation and emission slit widths were set at 5.0nm. In addition, the emission and excitation wavelengths were both set from 250 to 600 nm with an increment of 10nm. For the UV-vis experiments, the concentrations of HAs in solution were 5 mg-C·L -1 . For the fluorescence spectral experiments, the concentrations of HAs in solution were 10 mg-C·L -1 in a quartz cell. 2.7 Experimental design A series of experiments were performed to study the effects of DNT dosage, pHs, HA concentrations, and Mw of HA on the total content and chemical fraction of Cd in sediments. One gram of sediments was placed into conical flasks with 273 mg-C·L -1 of HA and various amounts of DNT (0.5, 1, 10, 20, 40, 60, 80, 100, 150, 200, 250, 300, 400, 600, 800, and 1000 mg). For comparison, we also prepared samples in which 1.00 g of sediments was placed in the conical flasks with the same amounts of DNT (0.5, 1, 10, 20, 40, 60, 80, 100, 150, 200, 250, 300, 400, 600, 800, and 1000 mg) in the absence of HA. Then, the mixtures were shaken at room temperature (initial pH = 7) for 96 h. Samples for determining the effects of HA concentrations on the total content and chemical fractions of Cd in sediments (1.00 g) were prepared at room temperature with 200 mg of DNT and various concentrations of HA (25, 50, 75, 100, 125, 150, 175, 200, 225, 250, and 273 mg-C·L -1 ) at an initial pH = 7 for 96 h. To determine the role of HA, 1.00 g of sediments was added to various concentrations of HA (25, 50, 75, 100, 125, 150, 175, 200, 225, 250, and 273 mg-C·L -1 ) without DNT at initial pH = 7 for 96 h. To investigate the effects of initial pH on the total content and chemical fractions of Cd in sediments, we studied a system with HA, a system with DNT, and a system with both DNT and HA. In the HA system, 1.00 g of sediments was added to 273 mg-C·L -1 of HA at various pHs (5, 6, 7, 8, and 9) at room temperature for 96 h. In the DNT system, 1.00 g of sediments was added to 200 mg of DNT at various pHs (5, 6, 7, 8, and 9) at room temperature for 96 h. In the DNT-HA system, 200 mg of DNT and 273 mg-C·L -1 of HA were added to a solution with 1.00 g of sediments at various pHs (5, 6, 7, 8, and 9) at room temperature for 96 h. One gram of sediments, 200 mg of DNT, and different Mw fractions of HA (UF1 = 25, 50, 75, 125, 175, 250, 350, 500, 700, 900, 1200, and 1700 mg-C L -1 , UF2 = 25, 50, 75, 125, 175, 250, 350, 500, and 700 mg-C L -1 ), UF3 = 25, 50, 75, 125, 175, 250, and 350 mg-C L -1 , UF4 = 25, 50, 75, 125, and 175 mg-C L -1 , UF5 = 25, 50, and 75 mg-C L -1 ) were reacted at room temperature (initial pH = 7) for 96 h to evaluate changes in the total content and chemical fractions of Cd in sediments. pH was measured after the reaction. The sediment was filtered using 0.45µm microporous membranes. All the experiments were performed in triplicate. 3. Results and discussion 3.1 Effects of dinotefuran dosage Migration, transformation, and degradation of DNT all affect its dosage in the environment (Ma et al., 2023). Hence, it is important to explore the effect of the DNT dosage on the total content and chemical fractions of Cd in sediments (Fig. 1). With an increase in the DNT dosage from 0.5 to 200 mg, the Cd content decreased from 5.568 to 4.802 mg·kg -1 , the F1 content ranged from 3.009 to 2.584 mg·kg -1 , the F2 content reduced from 1.020 to 0.729 mg·kg -1 , and the F3 and F4 content remained at about 0.488 mg·kg -1 and 1.004 mg·kg -1 , respectively (Fig. 1(a)). At higher dose of 200 to 1000 mg DNT, no significant changes were observed in the total content of Cd (about 4.762 mg·kg -1 ) and individual chemical fractions of Cd (F1 ≈ 2.541 mg·kg -1 , F2 ≈ 0.719 mg·kg -1 , F3 ≈ 0.482 mg·kg -1 , and F4 ≈ 1.019 mg·kg -1 ) in sediments. Changes in the total content and chemical fraction of Cd in sediments in the presence of various doses of DNT and HA are shown in Fig. 1(b). The total content of Cd gradually descended from 5.154 (for 0.5 mg DNT) to 4.726 mg·kg -1 (for 200 mg DNT), and remained constant at 4.578 mg·kg -1 over DNT dose range of 200–1000 mg. The F1 content decreased from 2.903 mg·kg -1 at 0.5 mg of DNT to 2.564 mg·kg -1 at 200 mg of DNT and remained constant at 2.492 mg·kg -1 at DNT doses of 200–1000 mg. For F2, the content ranged from 0.998 mg·kg -1 at 0.5 mg of DNT to 0.879 mg·kg -1 at 200 mg of DNT, keeping about 0.801 mg·kg -1 at DNT doses of 200–1000 mg. In contrast, the F3 ( ≈ 0.508 mg·kg -1 ) and F4 ( ≈ 0.772 mg·kg -1 ) content did not change significantly with differing doses of DNT. The total Cd content in sediments with both DNT and HA was lower than that with only DNT. Thus, HA promoted release of Cd from the sediment into the water. We also found the change of DNT dosage mainly affected the F1 and F2 chemical fractions of Cd in sediments. Interestingly, the F1 fraction of the total Cd content remained between 53.866% and 54.943% with exposure to DNT alone or with HA (Fig. 1(c) and (d)). In contrast, the F2 fraction of Cd in sediments slowly decreased with an increase in the dose of DNT from 0.5 to 200 mg. Therefore, DNT has a strong effect on F2 fraction. One possible reason is due to the notable impact of DNT on the pH, which affects Cd release and the Cd chemical fractions (Beesley et al., 2014; Wang et al., 2014). As the pH increased (Eh decreased) with addition of DNT, Mn(IV) oxides and Fe(Ⅲ) oxides were reduced to soluble Mn(II) and Fe(II), respectively (Guo et al., 1997). Stable fractions of Fe-Mn oxide-associated Cd in sediments were converted into mobile water-soluble and exchangeable Cd fraction. DNT dosage greater than 200 mg had no further effect on the chemical fraction of Cd. Therefore, 200 mg of DNT was selected as an appropriate dose for treated sediments in subsequent experiments. Please insert FTIR spectra (Fig. 2(a)) were used to obtain information on binding of functional groups when HA interacted with DNT. The characteristic absorption peak at 3440 cm -1 is related to the stretching vibration of the N-H bond of amino groups and the O-H bond of phenol (Rostami et al., 2023). The broad peak at 2440 cm -1 is attributed to the carboxyl group (Pan et al., 2021). In the DNT-HA system, the absorption peak at 1660 cm -1 corresponds to the amide I band and the C=O stretching of quinone or ketone (Zhao et al., 2022). These result show successful formation of complexes of HA and DNT. In the DNT-HA system, the characteristic absorption peak position was consistent with the results of Pan et al. (2021). The peak position at 1380 cm -1 was enhanced after the reaction, due to complexation of surface oxygen-containing and nitrogen-containing functional groups with Cd (Fig. 2(b)). The change in the FTIR spectra of DNT-HA before and after treatment of the sediment reveals the formation of Cd complexes (Fig. 2(b)). Please insert UV-vis spectra of interactions between HA and various DNT doses are shown in Fig. 3(a). As the dose of DNT increased, the UV-vis absorption in tensity for DNT-HA increased steadily, indicating increased formation of the complex, consistent with the FTIR spectra results. The fluorescence of HA was quenched by DNT; the quenching mechanism of HA fluorescence by DNT was verified using the Stern-Volmer equation [1] (Yu et al., 2015) (Fig. 3(b)). The K q values were >2.0×10 10 L·(mol·s) -1 (Xu et al., 2013) (Table 2), revealing that the quenching mechanism of HA and DNT was static quenching. The modified double logarithmic equations [2] and [3] (Veeralakshmi et al., 2017) were used to estimate the binding constant (log K a ) and the number of binding sites (n) for a binding process involving HA and DNT (Table 2). The binding constants decreased with increasing DNT doses of 0–150 mg, but increased with increasing DNT doses of 200–300 mg. However, the binding site values for the HA and DNT systems were all ~1, indicating there is only one binding site in the binding process involving HA and DNT where F 0 and F are the fluorescence intensities in the absence and presence of dinotefuran, respectively. K q is the bimolecular quenching constant, τ 0 is the average lifetime of the DNT-HA system of 5.75 ns (Pan et al., 2021), [ Q ] is the concentration of DNT, K a is the binding constant, and n is the number of binding sites. Please insert Please insert 3.2 Effects of humic acid concentration Figure 4 shows the effect of the HA concentration on the total content and chemical fractions of Cd in sediments. When DNT and HA were both present, the content of total Cd, F1, and F2 noticeably decreased with increases in the HA concentration, but the F3 and F4 content showed little change. Whereas for HA alone (Fig. 3(c) and (d)), an increase in the HA concentration considerably reduced the content of total Cd and F1, but had no significant effect on F2, F3, or F4 content. Unexpectedly, the percentage of F1 (about 53.035%) was almost constant, while the percentage of F2 significantly decreased with an increase in the HA concentration when both DNT and HA were present (from 21.860% of 25 mg-C·L -1 to 18.410% of 273 mg-C·L -1 ). The most common reaction between HA and the metal ions (Cd 2+ ) was the cation exchange reaction, as shown in equation [4] (Helal et al., 2006). The main interaction of DNT with HA is through an anion exchange reaction (Eq. 5); however, H-bonding also occurs between the amino group of DNT and OH or C=O groups of HA (Helal et al., 2006). However, the exchange reaction between DNT and HA uses the same binding sites that bind HA to Cd. This was the main reason that the sediment released more Cd with HA alone than in the presence of both HA and DNT. Please insert 3.3 Effects of pH Fig. 5 shows the effect of pH on the total content and chemical fractions of Cd in sediments with DNT alone, HA alone, and with both DNT and HA. The total content of Cd in the different systems was as follows: DNT > DNT and HA > HA. In addition, the content of total Cd, F1, and F2 in sediments increased with increasing pH from 5 to 7, while remaining constant at pH 8–9. No significant differences in the F3 and F4 fractions were observed. Previous studies have demonstrated that the binding constants of DNT-HA at pH 5, 6, 7, 8, and 9 were 20.58×10 3 , 41.95×10 3 , 76.50×10 3 , 25.10×10 3 , and 34.45×10 3 L·mol -1 (Pan et al., 2021), respectively. The weak binding ability of HA and DNT under acidic conditions was apparent, with higher concentrations of HA promoting release of Cd from sediments. Lower pHs reduced the negative surface charge on the sediment and enhanced dissolution of Fe/Mn oxides and carbonates in sediments, increasing the release of Cd (Perez-Esteban et al., 2013). Under alkaline conditions, negatively charged HA created electrostatic repulsion, giving HA a strong affinity to DNT. Consequently, HA provided fewer binding sites for Cd in the sediment. The chemical fraction of Cd in sediments at different pHs in the same system exhibited only slight differences. Please insert 3.4 Effects of the humic acid molecular weight The basic properties of different molecular weight of the humic acid were shown in Table 3. The composition analysis showed that the largest proportion of the Mw (48.20 wt.%) consisted of UF5; UF4, UF3, UF2, and UF1 made up 9.65 wt.%, 11.60 wt.%, 13.90 wt.%, and 16.65 wt.%, respectively. The DOCs of pristine-HA and the five HA Mw fractions were 273.00, 82.20, 236.20, 481.40, 822.40, and 1956.80 mg·L -1 , respectively. Lower Mw fractions of HA contained more phenolic and carboxylic functional groups than the higher Mw fractions. Specific UV absorbances (E 2 :E 3 ) decreased and the absorbance at 280 nm (SUVA 280 ) increased with an increase in the Mw, indicating that Mw fractions >100 kDa of HA had more aromatic components. Please insert Effects of the Mw of HA on the release of Cd from the sediments are presented in Fig. 6. Release rate of Cd from the sediments generally increased with increasing Mw and with increasing HA concentration. However, when the HA Mw was 1–10 kDa or <1 kDa HA, there were no significant changes in the release of Cd from the sediment with increasing HA concentration. Please insert 3.4.1 Humic acid molecular weights more than 100 kDa The total content of Cd in the sediment decreased gradually from 5.232 mg·kg -1 of 25 mg-C·L -1 to 4.021 mg·kg -1 of 1700 mg-C·L -1 for Mw > 100 kDa HA with 200 mg DNT (Fig. 7(a)). As the HA concentration increased from 25 to 1700 mg-C·L -1 , the F1 and F2 content in the sediment decreased gradually from 2.709 to 1.976 mg·kg -1 , and from 1.225 to 0.663 mg·kg -1 , respectively. The F1 fraction accounted for approximately 51.381% of the total Cd content from 25 to 1700 mg-C·L -1 for HA Mw >100 kDa (Fig. 7(b)). In contrast, the F2 fraction of Cd decreased from 23.410% of 25 mg-C·L -1 to 16.490% of 1700 mg-C·L -1 . After treatment with UF1-DNT, the F3 and F4 fractions of Cd in sediments were stable at content of 0.581 mg·kg -1 and 0.739 mg·kg -1 , respectively. However, the percentages of F3 and F4 increased with an increase in the UF1 concentration (Fig. 7(b)), due to the decrease in total Cd content. 3.4.2 Humic acid molecular weights of 30–100 kDa and 10–30 kDa For HA Mw of 30–100 kDa with 200 mg DNT, the F1 fraction of Cd in sediments decreased from 2.688 mg·kg -1 of 25 mg-C·L -1 to 2.302 mg·kg -1 of 700 mg-C·L -1 . The F2 fraction of Cd decreased from 1.303 mg·kg -1 of 25 mg-C·L -1 to 0.824 mg·kg -1 of 700 mg-C·L -1 . However, the F3 and F4 fractions of Cd maintain relatively constant content of 0.580 mg·kg -1 and 0.758 mg·kg -1 , respectively (Fig. 7(c)). For HA Mw of 10–30 kDa with 200 mg DNT, the F1 fraction decreased from 2.911 mg·kg -1 of 25 mg-C·L -1 to 2.709 mg·kg -1 of 350 mg-C·L -1 , the F2 fraction decreased from 1.263 mg·kg -1 of 25 mg-C·L -1 to 1.104 mg·kg -1 of 350 mg-C·L -1 , and the content of the F3 and F4 fractions were approximately 0.584 mg·kg -1 and 0.756 mg·kg -1 , respectively (Fig. 7(e)). The total Cd content decreased from 5.316 mg·kg -1 for 25 mg-C·L -1 to 4.481 mg·kg -1 for 700 mg-C·L -1 with 30–100 kDa HA, and was reduced from 5.504 mg·kg -1 for 25 mg-C·L -1 to 5.133 mg·kg -1 for 350 mg-C·L -1 with 10–30 kDa HA. 3.4.3 Humic acid molecular weights of 1–10 kDa and <1 kDa As the UF4 concentration increased from 25 to 175 mg-C·L -1 , the content of the F1, F2, F3, and F4 fractions of Cd in sediments were 2.962–2.887 mg·kg -1 , 1.306–1.264 mg·kg -1 , 0.566–0.548 mg·kg -1 , and 0.752–0.737 mg·kg -1 , respectively. For HA Mw of <1 kDa, the Cd content and chemical fraction in sediments did not change significantly with the HA concentration. Please insert 3.4.4 Mechanism of interaction between various molecular weight humic acids and dinotefuran Based on the above results, the content of total Cd, F1, and F2 in sediments decreased with increasing concentration of HAs with Mws of >100 kDa, 30–100 kDa, and 30–10 kDa. At these HA Mws, the F1 fraction of Cd in the sediments remained at ~52.100%, while the F2 fraction of Cd in the sediments decreased with increasing concentration of HAs. In contrast, HA with Mws of 1–10 kDa and <1 kDa in the presence of 200 mg DNT did not significantly influence Cd chemical fractionation or total Cd content. For example, for 75 mg-C·L -1 HA with added DNT, a notable increase in the Cd content in sediments was observed with decreasing HA Mw from >100 kDa to <1 kDa (Fig. 8). Higher Mw HAs have more aromatic components and active adsorption sites; their higher logK (stability constant for complexation between Cd 2+ and humic-like substances) reflects their stronger binding affinity for Cd 2+ (Bai et al., 2018; Gao et al., 2022). Please insert FTIR and three-dimensional fluorescence spectra were used to further investigate the functional groups and interactions in the system. FTIR spectra of the DNT-HA system with various HA Mws are shown in Fig. 9. An N-H stretch at approximately 3300 cm -1 and C-H stretches at 2877 and 2951 cm -1 (Maha et al., 2017) were observed in the FTIR spectrum of DNT. Compared with the DNT-HA system, the appearance of the N-H peak at 3300 cm -1 and C-H peaks at 2877 and 2951 cm -1 indicates that a hydrogen bonding interaction occurred between DNT and the HAs. The FTIR spectrum of the HAs was characterized by aromatic C=C, COO-, and H-bonded C=O stretches at ~1630 cm -1 (He et al., 2016). The band at ~1400 cm -1 was assigned to COO- antisymmetric stretching of the HAs (Christl et al., 2000). The DNT-HA spectrum showed a weak shift at the 1630 cm -1 peak and disappearance of the 1400 cm -1 peak, indicating that hydrogen bonding interactions occurred between N-H of DNT and COO- of HA. Please insert To further investigate the intensity and positions of the fluorescence peaks, three-dimensional fluorescence spectra (Zhou et al., 2021; Ding et al., 2022) were obtained to characterize the pristine HA mixture and different Mw HAs. Dynamic changes in the structures and compositions of the different Mw HAs interacting with DNT were investigated. Three-dimensional fluorescence spectra of the pristine HA mixture and different Mw HAs (75 mg-C·L -1 ) with and without addition of DNT (200 mg) at pH 7.0 are shown in Fig. 10. Pristine HA without addition of DNT had a stronger peak intensity at the excitation wavelength (E x ) of 280 nm and the emission wavelength (E m ) of 485 nm (Fig. 10(a)). The fluorescence intensities of the different MW HAs increased with decreasing Mw, potentially because the lower Mw HAs have higher concentrations of electron-donating groups, such as hydroxyl and methoxyl groups (Gao et al., 2022). Furthermore, the peak positions of different Mw HAs showed a detectable blue-shift with decreasing Mw, reflecting the reduced number of aromatic rings (Ren et al., 2017). This result agreed well with the UV-vis spectra trends. With the addition of 200 mg DNT (Fig. 10(a 1 –f 1 )), the three-dimensional fluorescence spectra of HA showed maxima at λE x /λE m = 450/520 nm (UF0), λE x /λE m = 440/510 nm (UF1), λE x /λE m = 440/500 nm (UF2), λE x /λE m = 370/450 nm (UF3), λE x /λE m = 360/440 nm (UF4), and λE x /λE m = 350/400 nm (UF5). The fluorescence intensity of the HAs was quenched by DNT and the peak positions of the HAs showed a red-shift. The decrease in fluorescence and peak shifts indicate that DNT bonding with the HAs induced some micro-environmental changes in the HAs. The modified Stern-Volmer model (Gao et al., 2022) was used to calculate the K q and K a values of HAs binding with DNT (Table 4). These values increased with increasing HA Mw. The relatively high Mw HAs had stronger adsorption affinity and complexing capacity for DNT than the low Mw HAs. Fig. 10 (a 2 –f 2 ) displays the three-dimensional fluorescence spectra of HAs with 200 mg DNT after sediment treatment. The fluorescence intensity of DNT and HAs with various Mws was clearly quenched after the treated sediments. The decreased peak intensities and blue-shifted peak positions indicated that electron-donating groups were removed, indicating that the most active fluorophores in the DNT-HA system were binding with Cd from the sediment. Please insert Please insert 4. Conclusions To investigate the effects of both DNT and HA on mechanisms of Cd migration and transformation in sediments, chemical sequential extraction, UV-vis, EEM, and FTIR techniques were employed to investigate changes in the content and chemical fraction of Cd in sediments. The main findings are as follows: Changes in the DNT dosage mainly affected the content of the F2 fraction of Cd in sediments for DNT dosage from 0.5 to 200 mg and had no effect on the chemical fractions of Cd for DNT dosage >200 mg. HA enhanced migration of Cd from sediment to water, significantly affecting only the F1 chemical fraction of Cd in the sediments. When both DNT and HA were present, the content of total Cd, F1, and F2 noticeably decreased with an increase in the HA concentration from 25 mg-C·L -1 to 273 mg-C·L -1 ; only minor changes in F3 and F4 content were apparent. When the pH increased from 5 to 7, total Cd, F1, and F2 content in sediments slightly increased. At pH 8 and 9, the content and chemical fraction of Cd in sediments did not change. In the presence of DNT and HA, the release rate of Cd from sediments increased with increasing Mw of HA from 100 kDa. The lower molecular weight of 1–10 kDa and 100 kDa, 30–100 kDa, and 10–30 kDa, the content of total Cd, F1, and F2 decreased with a increase in concentrations of HAs. Therefore, it is important to consider the humic acid with molecular weight greater than 10 kDa in the water environment for the partitioning and transformation of Cd from sediment. Declarations Authors Contributions BMY (student) has analyzed and interpreted the results. WHB performed the scientific work and was a major contributor in writing the manuscript. LSF contributed to writing the manuscript. YSH read the final manuscript. Availability of data and materials All data generated or analyzed during this study are included in this published article (and its supplementary information files). Funding This project was supported by the National Key Research and Development Program of China (2017YFD0800301), the National Natural Science Foundation of China (Grant No. 41703129), Liaoning Province Education Administration (No. LJ2020008, LQ2020023, and LJKMZ20220763). Ethics approval and consent to participate Not applicable. Consent to publish Not applicable. Competing interests The authors declare no competing interests. References Abdel-Ghany M. F., Hussein L. A., Azab N. F. E., 2017. Novel potentiometric sensors for the determination of the dinotefuran insecticide residue levels in cucumber and soil samples, TALANTA. 164, 518-528. https://doi.org/10.1016/j.talanta.2016.12.019. Bai B.C., Jiang Z.M., He M.J., Ye B.Y., Wei S.Q., 2018. Relating Cd 2+ binding by humic acids to molecular weight: A modeling and spectroscopic study volume. J. ENVIRON. SCI., 30, 154-165. https://doi.org/10.1016/j.jes.2017.11.028. Barriuso E., Baer U., Calvet R., 1992. 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Fraction Extractant solution Experimental conditions F1 Exchangeable/acid soluble fraction (bound to carbonates) 0.11 mol/L HAc (40 mL) Shaken for 18 h (22 ± 2°C); sediment to solution = 1:40 F2 Reducible fraction (bound to Mn and Fe oxides) 40 mL of 0.5 mol/L NH 3 OHCl (adjusted with HNO 3 to pH 2) Shaken for 18 h (22 ± 2°C); sediment to solution = 1:40 F3 Oxidizable fraction (bound to organic matter and sulfides) 8.8 mol/L H 2 O 2 2) 50 mL of 1 mol/L CH 3 COONH 4 (adjusted with HNO 3 to pH 2 1) Heated at 85 ± 2°C using a water bath for 2 h; sediment to solution = 1:10 (repeat twice); 2) Shaken for 18 h (22 ± 2 °C); sediment to solution = 1:50 F4 Residual fraction - The total Cd concentration minus F1–F3; concentrations of F1, F2, and F3 were determined using an atomic absorption spectrophotometer Table 2 Stern-Volmer quenching constants for DNT-HA. Entry Dose (mg) Q (mol·L -1 ) K q (×10 11 ) K a (×10 3 ) n 1 10 1.98×10 -4 0.812 0.427 0.999 2 20 3.96×10 -4 0.743 0.467 0.996 3 40 7.91×10 -4 0.672 0.386 1.000 4 60 1.19×10 -3 0.663 0.381 0.998 5 100 1.98×10 -3 0.529 0.304 1.000 6 150 2.97×10 -3 0.487 0.280 1.000 7 200 3.96×10 -3 0.499 0.287 0.999 8 250 4.95×10 -3 0.791 0.455 0.999 9 300 5.93×10 -3 0.832 0.478 1.000 Table 3 The basic properties of different molecular weight of the humic acid. Treatment HAs (kDa) Percentage (wt.%) Carboxyl group (mmol·g -1 ) Phenolic group (mmol·g -1 ) Total acidity (mmol·g -1 ) DOC (mg·L -1 ) SUVA 280 a (L·mg C -1 ·m -1 ) E 2 :E 3 b 1 Pristine HA (UF0) － 32.85 11.34 44.19 273.00 10.17 2.45 2 ＞100 (UF1) 16.65 33.75 10.80 44.55 1956.80 11.45 2.49 3 30-100 (UF2) 13.90 34.88 11.70 46.58 822.40 11.20 2.50 4 10-30 (UF3) 11.60 36.90 12.78 49.68 481.40 10.54 2.79 5 1-10 (UF4) 9.65 38.25 20.85 59.10 236.20 3.76 3.10 6 ＜1 (UF5) 48.20 37.35 22.96 60.31 82.20 1.00 3.22 a Specific ultraviolet (UV) absorbance at 280 nm b Ratio between the specific UV absorbances at 250 and 365 nm Table 4 Stern-Volmer quenching constants for the Mw of HAs and DNT. Entry Mw K q (×10 11 ) K a (×10 3 ) n 1 UF1 0.494 0.284 0.999 2 UF2 0.623 0.358 1.001 3 UF3 0.940 0.540 1.000 4 UF4 1.300 0.747 0.999 5 UF5 10.300 5.942 1.000 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4127483","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":298566912,"identity":"c4f344ff-8938-4b4d-a7a6-c20f0d7f7c45","order_by":0,"name":"Haibo Wang","email":"","orcid":"","institution":"Shenyang University of Chemical Technology","correspondingAuthor":false,"prefix":"","firstName":"Haibo","middleName":"","lastName":"Wang","suffix":""},{"id":298566913,"identity":"f68ba8a9-4e54-419d-935c-5ce7ada3420d","order_by":1,"name":"Mengyang Bian","email":"","orcid":"","institution":"Shenyang University of Chemical Technology","correspondingAuthor":false,"prefix":"","firstName":"Mengyang","middleName":"","lastName":"Bian","suffix":""},{"id":298566914,"identity":"26ee0b8a-e116-4d12-b82f-1f5d76a47c57","order_by":2,"name":"Shuhua Yao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvUlEQVRIie3QoQ7CMBCA4S5NiinTJRDGI5TsBXiUomYYklSCuRkeYILwGOhrsIXZJRgeADE5B5UgSE6S0N9dcp+4YywW+8kkw84+p2JQIZkkrvY8T6U3ZMLPQ+DLo1poGtDNBQMRBShmWG9PBNKujTtcZQnjHSZ7f6MQqfGxUSVM0PAEKKTxGqXQhVBGEwmutJNgDJ2M2kBqj3MIT3akW9LG511nMcuqyt17SyAzfBvwy9Jn2Za0FovFYn/dC9iQQ0EgdwcVAAAAAElFTkSuQmCC","orcid":"","institution":"Shenyang University of Chemical Technology","correspondingAuthor":true,"prefix":"","firstName":"Shuhua","middleName":"","lastName":"Yao","suffix":""},{"id":298566915,"identity":"9156270a-38d3-4fa3-9d8f-0396f7ee562f","order_by":3,"name":"Shifeng Li","email":"","orcid":"","institution":"Shenyang University of Chemical Technology","correspondingAuthor":false,"prefix":"","firstName":"Shifeng","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2024-03-19 05:39:56","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4127483/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4127483/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":56159533,"identity":"7dd9e3fe-92b5-4768-bb44-829e47e30816","added_by":"auto","created_at":"2024-05-09 09:05:03","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":161840,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of DNT dosage on the content and chemical fractions of Cd in the sediment alone (a) and in combination with HA (b).\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/359116cb0acba82b9dd9532a.jpg"},{"id":56160182,"identity":"3af86083-e162-4f52-8b6c-a6f296a58b61","added_by":"auto","created_at":"2024-05-09 09:13:03","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":75375,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of HA, DNT, and HA-DNT (a); the FTIR spectra of DNT-HA before and after treatment of the sediment (b).\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/df7a2735d1b2384fc1bd62f8.jpg"},{"id":56159181,"identity":"f38184b5-d48f-4ba4-9ef6-7c15486febe0","added_by":"auto","created_at":"2024-05-09 08:57:03","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":62708,"visible":true,"origin":"","legend":"\u003cp\u003eUV-vis spectra (a) and fluorescence emission spectra (b) of DNT-HA with various doses of DNT (0, 10, 20, 40, 60, 100, 150, 200, 250, and 300 mg (a–j)).\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/c9d2d06f65a561270cb0593c.jpg"},{"id":56159541,"identity":"e8767697-5092-4a56-8229-e425aa5e5504","added_by":"auto","created_at":"2024-05-09 09:05:04","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":186221,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of the HA concentration on the chemical fractions of Cd in sediment with both DNT and HA (a, b), and with HA alone (c, d).\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/c37c2b5ca7f578b8d800e323.jpg"},{"id":56160551,"identity":"0759cac7-b183-443e-b155-5902bfef9098","added_by":"auto","created_at":"2024-05-09 09:21:03","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":80204,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of the Mw of HA on release of Cd from the sediments.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/3978e6b3f5c38a0e0cd2b7cd.jpg"},{"id":56161133,"identity":"a7c8d36e-3a5c-4945-911b-6de4ebb745a2","added_by":"auto","created_at":"2024-05-09 09:29:03","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":88170,"visible":true,"origin":"","legend":"\u003cp\u003eCd concent and chemical fraction in sediments with 75 mg-C·L\u003csup\u003e-1\u003c/sup\u003e HAs in the presence of DNT.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/cb254918efb61e2de1bf8ed8.jpg"},{"id":56159190,"identity":"f7ab269f-511d-4347-9d1a-bce81c77af0e","added_by":"auto","created_at":"2024-05-09 08:57:04","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":126066,"visible":true,"origin":"","legend":"\u003cp\u003eThree-dimensional fluorescence spectra of pristine HA and various Mws of HA (75 mg-C·L\u003csup\u003e-1\u003c/sup\u003e) with and without addition of DNT (200 mg) at pH 7.0. (a–f) without addition of DNT; (a\u003csub\u003e1\u003c/sub\u003e–f\u003csub\u003e1\u003c/sub\u003e) with 200 mg DNT before sediment treatment; (a\u003csub\u003e2\u003c/sub\u003e–f\u003csub\u003e2\u003c/sub\u003e) with 200 mg DNT after sediment treatment.\u003c/p\u003e","description":"","filename":"10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/79e45a9993a030fc5a01c2a6.jpg"},{"id":72216957,"identity":"eae62fb9-ac6e-4bd2-88da-ed3210381b0e","added_by":"auto","created_at":"2024-12-23 20:11:28","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1345698,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4127483/v1/81ab29dc-c4e4-459d-a12c-ada7fea79a3b.pdf"}],"financialInterests":"","formattedTitle":"Effects of dinotefuran and humic acid on cadmium migration and transformation in sediments","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCadmium (Cd) is a highly mobile and toxic element that has substantial deleterious effects on aquatic ecosystems and human health, raising serious public concern in many parts of the world (Wang et al., 2016; Jalali et al., 2021; Wang et al., 2023; Zarei et al., 2023). Cd content in aquatic ecosystems have become elevated due to increasing discharges of urban, agricultural, and industrial wastewater (Tian et al., 2020). After Cd enters the aquatic environment, it is mainly sequestered in the sediment through various adsorption and absorption processes (Rajeshkumar et al., 2018; Jaskuła and Sojka, 2022), causing Cd to become enriched in sediments. Changes in aquatic parameters such as dissolved oxygen (Liu et al., 2022), dissolved organic matter (Wang et al., 2010), pesticides (Wang et al., 2016), salinity (Jia et al., 2021), pH, and redox potential (Wang et al., 2023) can release Cd from sediments, leading to secondary pollution of overlying waters.\u003c/p\u003e\n\u003cp\u003eThe extensive use of pesticides has led to widespread contamination of aquatic ecosystems (Mitchell et al., 2017), neonicotinoid pesticides are currently the most widely used class of pesticides in the world (Gutiérrez-Sánchez et al., 2017). Neonicotinoid pesticides are ubiquitous in aquatic systems at concentrations that exceed the regulatory guidelines of the USA and Canada, as well as ecotoxicological thresholds for many beneficial organisms (Wolfram et al., 2018; Borsuah et al., 2020). Neonicotinoid pesticides can compete with Cd for the same binding sites on sediment surface through electrostatic interactions and hydrogen bonding (Wang et al., 2016). In addition, neonicotinoid pesticides can directly form new compounds with Cd, which are then adsorbed onto sediments (Wang et al., 2016; Singh et al., 2017). Moreover, neonicotinoid pesticides can release H\u003csup\u003e+\u003c/sup\u003e, altering sediment pH, which may indirectly accelerate or inhibit the release of Cd from the sediments (Yu et al., 2019).\u003c/p\u003e\n\u003cp\u003eHumic acid (HA) is the main component of dissolved organic matter and is ubiquitous in aquatic environments (Wang et al., 2021; Liu et al., 2023). HA is one of the most important participants in the global carbon cycle (Schmidt et al., 2011). HA has a porous and loose spongy structure with a large surface area and many reactive sites\u0026nbsp;(Campitelli et al., 2006). It contains various reactive functional groups, such as carbonyl, carboxyl, and phenolic hydroxyl groups, as well as peptide and sugar fragments with polyelectrolyte/polybiszeolite properties\u0026nbsp;(Samios et al., 2007; Xu et al., 2022). These reactive groups affect partitioning and transformation of Cd and neonicotinoid pesticides via adsorption, complexation, and redox processes (Barriuso et al., 1992; Helal et al., 2006). Interactions between HA and neonicotinoids have received public and regulatory attention due to their effects on the environmental behavior of pollutants in aquatic ecosystems. Pan et al.\u0026nbsp;(2021) reported neonicotinoid pesticides (dinotefuran, clothianidin, and nitenpyram) could quench the endogenous fluorescence of HA through a static quenching process dominated by hydrogen bonds and van der Waals forces. Ćwieląg-Piasecka et al. (2018) found that HA exhibits high affinity for polar, ionic pesticides with high water solubility, which can be adsorbed via specific interactions with HA functional groups. Liu et al. (2018)\u0026nbsp;reported that HA contains a variety of functional groups that act as adsorption sites, regulating pesticide adsorption onto the soil surface.\u003c/p\u003e\n\u003cp\u003eFocusing only on the toxicity of individual constituents introduces uncertainty in ecological risk assessment; it is important to consider that interactions between HA and neonicotinoids may alter their individual behavior. The sediment-water system is very sensitive; both HA and neonicotinoids may greatly influence the mobility and transport of Cd from the sediment into the water, posing additive or synergistic ecological and environmental risks. DNT is a third-generation neonicotinoid pesticide with relatively high solubility and persistence, with commensurately greater risks to aquatic ecosystems (Lu et al., 2023). No systematic studies have been conducted evaluating the release of Cd from the sediment in water-sediment systems under co-exposure to DNT and HA. The objectives of the current study were to (1) systematically study the effects of pH, dissolved organic carbon (DOC), the molecular weight (Mw) of HA, and dose of DNT on release of Cd from the sediment, (2) evaluate changes in the chemical fraction of Cd in sediments under DNT and HA co-exposure from simple to complex systems, and (3) elucidate the mechanisms and controlling factors of Cd chemical fraction changes with interactions between DNT and HA. This study provides theoretical information and support for health risk assessment of co-exposure to these chemicals in aquatic environments.\u003c/p\u003e"},{"header":"2. Materials and methods ","content":"\u003cp\u003e2.1. Reagents\u003c/p\u003e\u003cp\u003eDNT (\u0026gt;98%) and HA were purchased from Mylin Technology Co., LTD. (Shanghai, China) and Sigma Corporation (Shanghai, China), respectively. Cadmium standard solution was purchased from the National Analysis and Testing Center for Metal and Electronic Materials (Shanghai, China). All other chemicals were analytically pure and purchased from Sinopharm Group Chemical Reagent Co., LTD. (Shanghai, China).\u003c/p\u003e\u003cp\u003e2.2 Sediments\u003c/p\u003e\u003cp\u003eSediment samples were collected at Dapan in the Xihe River Basin, Shenyang City, Liaoning Province (41° 66' N, 123° 11' E). Surface sediments (a depth of 0–20 cm) were collected using a plastic grab sampler and packed into polyethylene sample bags. The samples were air-dried, ground using an agate mortar, sieved with a 200-mesh nylon sieve, and stored at -20℃ for subsequent experiments.\u003c/p\u003e\u003cp\u003eTen grams of sediment were placed in a beaker containing 25 mL of CaCl\u003csub\u003e2\u003c/sub\u003e solution (0.01 M). The beaker was sealed with plastic wrap and shaken at room temperature for 30 min.\u0026nbsp;\u003c/p\u003e\u003cp\u003e2.3 Cadmium analysis\u003c/p\u003e\u003cp\u003eSediments (0.10 g) were digested in 3 mL of HNO\u003csub\u003e3\u003c/sub\u003e-HF (molar ratio 1:2) acid solution at 190°C for 24 h. After cooling, the solution was heated with an electric heating plate (200°C) until no liquid remained. Then, 5 mL of 68 wt.% HNO\u003csub\u003e3\u003c/sub\u003e solution was added and the solution was held at 130°C for 3 h. Finally, the digested sample was filtered through a 0.45μm microporous membrane and diluted in a 25 mL volumetric flask. An atomic absorption spectrophotometer (AA-6880, Shimadzu, Japan) was used to measure the Cd content of the final samples. The total content of Cd in the original sediments was 5.90 mg·kg\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e2.4 Chemical fraction of Cadmium\u003c/p\u003e\u003cp\u003eThe European Community Bureau of Reference (BCR) sequential extraction method\u0026nbsp;(Pueyo et al. 2001)\u0026nbsp;was employed to study the chemical fractions of Cd in the sediments (Table 1;\u0026nbsp;Wang et al., 2022).\u003c/p\u003e\u003cp\u003ePlease insert \u0026lt; Table 1\u0026gt;\u003c/p\u003e\u003cp\u003e2.5Molecular weight of\u0026nbsp;the humic acid\u003c/p\u003e\u003cp\u003eHA (0.20 g) was dissolved in 200 mL of KOH (0.02 M), then filtered through a 0.45-mm filtration membrane\u0026nbsp;(Liu\u0026nbsp;\u0026amp;\u0026nbsp;Cai, 2010). The above solution (defined as pristine-HA, UF0) was\u0026nbsp;divided into Mw fractions of\u0026nbsp;\u0026gt;100 kDa (UF1), 30–100 kDa (UF2), 10–30 kDa (UF3), 1–10 kDa (UF4), and \u0026lt;1 kDa (UF5)\u0026nbsp;using an ultrafiltration Amicon stirred cell (UFSC20001; Beverley, MA, USA)\u0026nbsp;(Ren et al., 2017)\u0026nbsp;technique with the nominal ultrafiltration membranes of 100, 30, 10 and 1 kDa (regenerated cellulose; diameter 63.50 mm; Millipore Corporation, Billerica, MA, USA). The\u0026nbsp;ultrafiltration separation was performed from 100 kDa to 1 kDa; the ratio of the bulk volume of the HA sample before ultrafiltration and the residual volume of HA on the membrane after ultrafiltration was 6:1. The concentration unit used for the HA fractions was the DOC concentration (TOC-VCSN; Shimadzu, JPN).\u003c/p\u003e\u003cp\u003e2.6 Characterization\u003c/p\u003e\u003cp\u003eUV-vis absorption spectra of HAs were collected using a P4 spectrophotometer (Shanghai, China). FTIR was performed in the range of 4000 to 400 cm\u003csup\u003e−1\u003c/sup\u003e. The FTIR spectra of HAs with and without DNT, and for DNT were measured on a Thermo Fisher Nicolet 6700 FTIR spectrometer (MA, USA) using potassium bromide pellets. The HA solutions containing different doses of DNT were scanned with a fluorescence spectrophotometer (PE-LS55, USA) in a 1cm quartz colorimeter. Both the excitation and emission slit widths were set to 10nm and the scanning speed was 800 nm/min. The excitation wavelength was set at 288nm and the emission wavelength was set at 250–600nm. Excitation emission matrix (EEM) spectra of HAs were scanned using an F-2700 fluorescence spectrometer (Joint-stock, Japan). For all of the above fluorescence measurements, the excitation and emission slit widths were set at 5.0nm. In addition, the emission and excitation wavelengths were both set from 250 to 600 nm with an increment of 10nm.\u0026nbsp;\u003c/p\u003e\u003cp\u003eFor the\u0026nbsp;UV-vis\u0026nbsp;experiments,\u0026nbsp;the concentrations of HAs in solution were 5\u0026nbsp;mg-C·L\u003csup\u003e-1\u003c/sup\u003e.\u0026nbsp;For\u0026nbsp;the fluorescence spectral experiments,\u0026nbsp;the concentrations of HAs in solution were 10\u0026nbsp;mg-C·L\u003csup\u003e-1\u003c/sup\u003e in a quartz cell.\u003c/p\u003e\u003cp\u003e2.7 Experimental design\u003c/p\u003e\u003cp\u003eA series of experiments were performed to study the effects of DNT dosage, pHs,\u0026nbsp;HA concentrations,\u0026nbsp;and\u0026nbsp;Mw of HA\u0026nbsp;on the total content and chemical fraction of Cd in sediments. One gram of sediments was placed into conical flasks with 273 mg-C·L\u003csup\u003e-1\u003c/sup\u003e of HA and various amounts of DNT (0.5, 1, 10, 20, 40, 60, 80, 100, 150, 200, 250, 300, 400, 600, 800, and 1000 mg). For comparison, we also prepared samples in which 1.00 g of sediments was placed in the conical flasks with the same amounts of DNT (0.5, 1, 10, 20, 40, 60, 80, 100, 150, 200, 250, 300, 400, 600, 800, and 1000 mg) in the absence of HA. Then, the mixtures were shaken at room temperature (initial pH = 7) for 96 h.\u0026nbsp;\u003c/p\u003e\u003cp\u003eSamples for determining the effects of HA concentrations on the total content and chemical fractions of Cd in sediments (1.00 g) were prepared at\u0026nbsp;room temperature\u0026nbsp;with 200 mg of DNT and various\u0026nbsp;concentrations of HA (25, 50, 75, 100, 125, 150, 175, 200, 225, 250,\u0026nbsp;and 273 mg-C·L\u003csup\u003e-1\u003c/sup\u003e) at an initial pH = 7 for 96 h. To determine the role of HA, 1.00 g of sediments was added to various concentrations of HA (25, 50, 75, 100, 125, 150, 175, 200, 225, 250, and 273 mg-C·L\u003csup\u003e-1\u003c/sup\u003e) without DNT at initial pH = 7 for 96 h.\u003c/p\u003e\u003cp\u003eTo investigate the effects of initial pH on the total content and chemical fractions of Cd in sediments, we studied\u0026nbsp;a system with\u0026nbsp;HA,\u0026nbsp;a system with DNT, and a system with both DNT and HA. In the HA system,\u0026nbsp;1.00 g of sediments was added\u0026nbsp;to\u0026nbsp;273 mg-C·L\u003csup\u003e-1\u003c/sup\u003e of HA at various pHs (5, 6, 7, 8, and 9) at room temperature for 96 h. In the DNT system, 1.00 g of sediments was added to 200 mg of DNT at various pHs (5, 6, 7, 8, and 9) at room temperature for 96 h. In the DNT-HA system, 200 mg of DNT and 273 mg-C·L\u003csup\u003e-1\u003c/sup\u003e of HA were added to a solution with 1.00 g of sediments at various pHs (5, 6, 7, 8, and 9) at room temperature for 96 h.\u003c/p\u003e\u003cp\u003eOne gram of sediments,\u0026nbsp;200 mg of DNT,\u0026nbsp;and different Mw fractions of HA (UF1 = 25, 50, 75, 125, 175, 250, 350, 500, 700, 900, 1200, and 1700 mg-C L\u003csup\u003e-1\u003c/sup\u003e, UF2 = 25, 50, 75, 125, 175, 250, 350, 500, and 700 mg-C L\u003csup\u003e-1\u003c/sup\u003e), UF3 = 25, 50, 75, 125, 175, 250, and 350 mg-C L\u003csup\u003e-1\u003c/sup\u003e, UF4 = 25, 50, 75, 125, and 175 mg-C L\u003csup\u003e-1\u003c/sup\u003e, UF5 = 25, 50, and 75 mg-C L\u003csup\u003e-1\u003c/sup\u003e) were reacted at room temperature (initial pH = 7) for 96 h to evaluate changes in\u0026nbsp;the total content and chemical fractions of Cd in sediments.\u003c/p\u003e\u003cp\u003epH was measured after the reaction. The sediment was filtered using 0.45µm microporous membranes. All the experiments were performed in triplicate.\u003c/p\u003e"},{"header":"3. Results and discussion ","content":"\u003cp\u003e3.1 Effects of dinotefuran dosage\u003c/p\u003e\n\u003cp\u003eMigration, transformation, and degradation of DNT all affect its dosage in the environment (Ma et al., 2023). Hence, it is important to explore the effect of\u0026nbsp;the DNT dosage on the total content and chemical fractions\u0026nbsp;of\u0026nbsp;Cd\u0026nbsp;in\u0026nbsp;sediments\u0026nbsp;(Fig. 1).\u0026nbsp;With an increase in the\u0026nbsp;DNT\u0026nbsp;dosage from 0.5 to 200 mg, the Cd content decreased from 5.568 to 4.802\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, the F1 content ranged from\u0026nbsp;3.009 to 2.584\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, the F2 content reduced from 1.020 to 0.729\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, and the F3 and F4 content remained at about 0.488\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e and 1.004\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, respectively (Fig. 1(a)). At higher dose of 200 to 1000 mg\u0026nbsp;DNT, no significant changes were observed in the total content of Cd (about 4.762\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e) and individual chemical fractions of Cd (F1\u0026nbsp;\u0026asymp;\u0026nbsp;2.541\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e,\u0026nbsp;F2\u0026nbsp;\u0026asymp;\u0026nbsp;0.719\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e,\u0026nbsp;F3\u0026nbsp;\u0026asymp;\u0026nbsp;0.482\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, and\u0026nbsp;F4\u0026nbsp;\u0026asymp;\u0026nbsp;1.019\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e) in sediments.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eChanges in the total content and chemical fraction\u0026nbsp;of\u0026nbsp;Cd\u0026nbsp;in\u0026nbsp;sediments\u0026nbsp;in the presence of various\u0026nbsp;doses of\u0026nbsp;DNT\u0026nbsp;and HA\u0026nbsp;are shown in Fig. 1(b). The total content of Cd gradually descended from 5.154 (for 0.5 mg DNT) to 4.726\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e (for 200 mg DNT), and remained constant at 4.578\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e over\u0026nbsp;DNT\u0026nbsp;dose range of 200\u0026ndash;1000 mg. The F1 content decreased from 2.903\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e at 0.5 mg of\u0026nbsp;DNT\u0026nbsp;to 2.564\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e at 200 mg of DNT\u0026nbsp;and remained constant at 2.492\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e at\u0026nbsp;DNT\u0026nbsp;doses of 200\u0026ndash;1000 mg. For F2, the content ranged from 0.998\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e at 0.5 mg of\u0026nbsp;DNT\u0026nbsp;to 0.879\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e at 200 mg of\u0026nbsp;DNT, keeping about 0.801\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e at\u0026nbsp;DNT\u0026nbsp;doses of\u0026nbsp;200\u0026ndash;1000\u0026nbsp;mg. In contrast, the F3 (\u0026nbsp;\u0026asymp;\u0026nbsp;0.508\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e) and F4 (\u0026nbsp;\u0026asymp;\u0026nbsp;0.772\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e) content did not change significantly with differing doses of\u0026nbsp;DNT.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe total Cd content in sediments with both\u0026nbsp;DNT\u0026nbsp;and HA was lower than that with only\u0026nbsp;DNT.\u0026nbsp;Thus, HA promoted release of Cd from the sediment into the water. We also found the change of\u0026nbsp;DNT\u0026nbsp;dosage mainly affected the F1 and\u0026nbsp;F2 chemical fractions\u0026nbsp;of Cd in sediments. Interestingly, the\u0026nbsp;F1 fraction of the total Cd content remained between 53.866% and 54.943% with\u0026nbsp;exposure to\u0026nbsp;DNT\u0026nbsp;alone or with\u0026nbsp;HA (Fig. 1(c) and (d)). In contrast, the\u0026nbsp;F2 fraction\u0026nbsp;of Cd in sediments slowly decreased with an increase in the dose of\u0026nbsp;DNT\u0026nbsp;from 0.5 to 200 mg.\u0026nbsp;Therefore,\u0026nbsp;DNT\u0026nbsp;has a strong effect on F2 fraction. One possible reason is due to the notable impact of\u0026nbsp;DNT\u0026nbsp;on the pH, which affects Cd release and the Cd chemical fractions (Beesley et al., 2014; Wang et al., 2014). As the pH increased (Eh decreased) with addition of\u0026nbsp;DNT, Mn(IV) oxides and Fe(Ⅲ) oxides were reduced to soluble Mn(II) and Fe(II), respectively (Guo et al., 1997). Stable fractions of Fe-Mn oxide-associated Cd in sediments were converted into mobile water-soluble and exchangeable Cd fraction. DNT dosage greater than 200 mg had no further effect on the chemical fraction of Cd. Therefore, 200 mg of\u0026nbsp;DNT\u0026nbsp;was selected as an appropriate dose for treated sediments in subsequent experiments.\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 1\u0026gt;\u003c/p\u003e\n\u003cp\u003eFTIR\u0026nbsp;spectra (Fig. 2(a)) were used\u0026nbsp;to obtain information on binding of functional groups when HA interacted with\u0026nbsp;DNT. The characteristic absorption peak at 3440 cm\u003csup\u003e-1\u003c/sup\u003e is\u0026nbsp;related to\u0026nbsp;the stretching vibration of the N-H bond of amino groups and the O-H bond of phenol\u0026nbsp;(Rostami et al., 2023). The broad peak at 2440\u0026nbsp;cm\u003csup\u003e-1\u003c/sup\u003e is\u0026nbsp;attributed to\u0026nbsp;the carboxyl group\u0026nbsp;(Pan et al., 2021).\u0026nbsp;In the\u0026nbsp;DNT-HA\u0026nbsp;system, the absorption peak at 1660\u0026nbsp;cm\u003csup\u003e-1\u003c/sup\u003e corresponds to the amide I band and the C=O stretching of quinone or ketone\u0026nbsp;(Zhao et al., 2022). These result show\u0026nbsp;successful formation of complexes of HA and DNT.\u0026nbsp;In the\u0026nbsp;DNT-HA\u0026nbsp;system, the characteristic absorption peak position was consistent with the results of\u0026nbsp;Pan et al. (2021). The peak position at\u0026nbsp;1380\u0026nbsp;cm\u003csup\u003e-1\u003c/sup\u003e was enhanced after the reaction, due to complexation of surface oxygen-containing and nitrogen-containing functional groups with Cd (Fig. 2(b)). The change in the FTIR spectra of\u0026nbsp;DNT-HA\u0026nbsp;before and after treatment of the sediment\u0026nbsp;reveals the formation of Cd complexes (Fig. 2(b)).\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 2\u0026gt;\u003c/p\u003e\n\u003cp\u003eUV-vis spectra of interactions between HA and various DNT doses are shown in Fig. 3(a). As the dose of DNT increased, the UV-vis absorption in tensity for DNT-HA increased steadily, indicating increased formation of the complex, consistent with the FTIR spectra results. The fluorescence of HA was quenched by DNT; the quenching mechanism of HA fluorescence by DNT was verified using the Stern-Volmer equation [1] (Yu et al., 2015) (Fig. 3(b)). The \u003cem\u003eK\u003c/em\u003e\u003csub\u003eq\u003c/sub\u003e values were \u0026gt;2.0\u0026times;10\u003csup\u003e10\u003c/sup\u003e L\u0026middot;(mol\u0026middot;s)\u003csup\u003e-1\u003c/sup\u003e (Xu et al., 2013) (Table 2), revealing that the quenching mechanism of HA and DNT was static quenching. The modified double logarithmic equations [2] and [3] (Veeralakshmi et al., 2017) were used to estimate the binding constant (log \u003cem\u003eK\u003c/em\u003e\u003csub\u003ea\u003c/sub\u003e) and the number of binding sites (n) for a binding process involving HA and DNT (Table 2). The binding constants decreased with increasing DNT doses of 0\u0026ndash;150 mg, but increased with increasing DNT doses of 200\u0026ndash;300 mg. However, the binding site values for the HA and DNT systems were all ~1, indicating there is only one binding site in the binding process involving HA and DNT\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\" width=\"562\" height=\"220\"\u003e\u003c/p\u003e\n\u003cp\u003ewhere \u003cem\u003eF\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e and \u003cem\u003eF\u003c/em\u003e are the fluorescence intensities in the absence and presence of dinotefuran, respectively. \u003cem\u003eK\u003c/em\u003e\u003csub\u003eq\u003c/sub\u003e is the bimolecular quenching constant, \u003cem\u003e\u0026tau;\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e is the average lifetime of the DNT-HA system of 5.75 ns (Pan et al., 2021), [\u003cem\u003eQ\u003c/em\u003e] is the concentration of DNT, \u003cem\u003eK\u003c/em\u003e\u003csub\u003ea\u003c/sub\u003e is the binding constant, and \u003cem\u003en\u003c/em\u003e is the number of binding sites.\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 3\u0026gt;\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Table 2\u0026gt;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2 Effects of humic acid concentration\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFigure 4 shows the effect of the HA concentration on the total content and chemical fractions of Cd in sediments.\u0026nbsp;When DNT and HA were both present,\u0026nbsp;the content of total Cd, F1, and F2 noticeably decreased with increases in the HA concentration, but the F3 and F4 content showed little change. Whereas for\u0026nbsp;HA alone (Fig. 3(c) and (d)), an\u0026nbsp;increase in the HA concentration considerably reduced the content of total Cd and F1, but had no significant effect on F2, F3, or F4 content.\u0026nbsp;Unexpectedly, the percentage of F1 (about 53.035%) was almost constant, while the percentage of F2 significantly decreased with an increase in the HA concentration when both\u0026nbsp;DNT\u0026nbsp;and HA were present\u0026nbsp;(from 21.860% of 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003eto 18.410% of\u0026nbsp;273\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e).\u0026nbsp;The most\u0026nbsp;common reaction between HA and the metal ions (Cd\u003csup\u003e2+\u003c/sup\u003e) was the cation exchange reaction, as shown in equation [4] (Helal et al., 2006). The main interaction of DNT with HA is through an anion exchange reaction (Eq. 5); however, H-bonding also occurs between the amino group of DNT and OH or C=O groups of HA (Helal et al., 2006). However, the exchange reaction between DNT and HA uses the same binding sites that bind HA to Cd. This was the main reason that the sediment released more Cd with HA alone than in the presence of both HA and DNT.\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" style=\"width: 543px; height: 91.1972px;\" width=\"543\" height=\"91.1972\"\u003e\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 4\u0026gt;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.3\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eEffects\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eof pH\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFig. 5 shows the effect\u0026nbsp;of pH on the total content and chemical fractions\u0026nbsp;of\u0026nbsp;Cd\u0026nbsp;in\u0026nbsp;sediments\u0026nbsp;with\u0026nbsp;DNT\u0026nbsp;alone, HA alone, and\u0026nbsp;with both DNT and HA.\u0026nbsp;The\u0026nbsp;total\u0026nbsp;content of Cd in the different systems was as follows:\u0026nbsp;DNT\u0026nbsp;\u0026gt;\u0026nbsp;DNT and HA\u0026nbsp;\u0026gt; HA.\u0026nbsp;In addition, the content of total Cd, F1, and F2 in sediments\u0026nbsp;increased with increasing pH from 5 to 7, while remaining constant at pH 8\u0026ndash;9. No significant differences in the F3 and F4 fractions were observed. Previous studies have demonstrated that the\u0026nbsp;binding constants\u0026nbsp;of\u0026nbsp;DNT-HA\u0026nbsp;at pH 5, 6, 7, 8, and 9 were 20.58\u0026times;10\u003csup\u003e3\u003c/sup\u003e, 41.95\u0026times;10\u003csup\u003e3\u003c/sup\u003e, 76.50\u0026times;10\u003csup\u003e3\u003c/sup\u003e, 25.10\u0026times;10\u003csup\u003e3\u003c/sup\u003e, and 34.45\u0026times;10\u003csup\u003e3\u003c/sup\u003e L\u0026middot;mol\u003csup\u003e-1\u003c/sup\u003e (Pan et al., 2021), respectively.\u0026nbsp;The weak binding ability of HA and\u0026nbsp;DNT\u0026nbsp;under acidic conditions was apparent, with higher concentrations of HA promoting release of Cd from sediments.\u0026nbsp;Lower pHs reduced the negative surface charge on the sediment and enhanced dissolution of Fe/Mn oxides and carbonates in sediments, increasing the release of Cd (Perez-Esteban et al., 2013).\u0026nbsp;Under alkaline conditions, negatively charged HA created electrostatic repulsion, giving HA a strong affinity to\u0026nbsp;DNT. Consequently, HA provided fewer binding sites for Cd in the sediment. The chemical fraction of Cd\u0026nbsp;in\u0026nbsp;sediments at\u0026nbsp;different\u0026nbsp;pHs in the same system\u0026nbsp;exhibited only slight differences.\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 5\u0026gt;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.4 Effects of the humic acid molecular weight\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe basic properties of different\u0026nbsp;molecular weight of the humic acid\u0026nbsp;were shown in Table 3.\u0026nbsp;The composition analysis showed that the largest proportion of the Mw (48.20 wt.%) consisted of\u0026nbsp;UF5; UF4, UF3, UF2, and UF1 made up 9.65 wt.%, 11.60 wt.%, 13.90 wt.%, and 16.65 wt.%, respectively.\u0026nbsp;The DOCs of\u0026nbsp;pristine-HA\u0026nbsp;and the five HA Mw fractions were 273.00,\u0026nbsp;82.20,\u0026nbsp;236.20,\u0026nbsp;481.40,\u0026nbsp;822.40,\u0026nbsp;and\u0026nbsp;1956.80\u0026nbsp;mg\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e, respectively.\u0026nbsp;Lower Mw fractions of HA contained more phenolic and carboxylic functional groups than the higher Mw fractions.\u0026nbsp;Specific UV absorbances\u0026nbsp;(E\u003csub\u003e2\u003c/sub\u003e:E\u003csub\u003e3\u003c/sub\u003e)\u0026nbsp;decreased and the absorbance at 280 nm (SUVA\u003csub\u003e280\u003c/sub\u003e) increased with an increase in the Mw, indicating\u0026nbsp;that Mw fractions \u0026gt;100 kDa of HA\u0026nbsp;had more aromatic components.\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Table 3\u0026gt;\u003c/p\u003e\n\u003cp\u003eEffects of the Mw of HA on the release of Cd from the sediments are presented in Fig. 6. Release rate\u0026nbsp;of Cd from the sediments generally\u0026nbsp;increased with increasing Mw\u0026nbsp;and\u0026nbsp;with increasing HA concentration. However, when the HA\u0026nbsp;Mw was 1\u0026ndash;10 kDa or \u0026lt;1 kDa HA, there were\u0026nbsp;no significant changes in the release of Cd from the sediment with\u0026nbsp;increasing HA concentration.\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 6\u0026gt;\u003c/p\u003e\n\u003cp\u003e3.4.1\u0026nbsp;Humic acid molecular weights\u0026nbsp;more than 100\u0026nbsp;kDa\u003c/p\u003e\n\u003cp\u003eThe total content of Cd in the sediment decreased gradually from\u0026nbsp;5.232 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003eto 4.021 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 1700\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e for Mw\u0026nbsp;\u0026gt; 100\u0026nbsp;kDa HA with 200 mg DNT (Fig. 7(a)).\u0026nbsp;As the HA concentration increased from\u0026nbsp;25 to 1700\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e, the F1 and F2 content in the sediment decreased gradually from\u0026nbsp;2.709 to 1.976 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, and from\u0026nbsp;1.225 to 0.663 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, respectively. The F1 fraction accounted for approximately 51.381% of the total Cd content from\u0026nbsp;25 to 1700\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003efor HA\u0026nbsp;Mw\u0026nbsp;\u0026gt;100\u0026nbsp;kDa\u0026nbsp;(Fig. 7(b)). In contrast,\u0026nbsp;the\u0026nbsp;F2 fraction\u0026nbsp;of Cd decreased from 23.410%\u0026nbsp;of 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 16.490%\u0026nbsp;of 1700\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e. After treatment with UF1-DNT, the F3 and F4 fractions of Cd in sediments were stable at content of 0.581 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e and 0.739 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, respectively.\u0026nbsp;However, the percentages of F3 and F4 increased with an increase in the UF1 concentration (Fig. 7(b)), due to the decrease in total Cd content.\u003c/p\u003e\n\u003cp\u003e3.4.2\u0026nbsp;Humic acid\u0026nbsp;molecular weights of\u0026nbsp;30\u0026ndash;100 kDa and 10\u0026ndash;30 kDa\u003c/p\u003e\n\u003cp\u003eFor HA\u0026nbsp;Mw of\u0026nbsp;30\u0026ndash;100 kDa with 200 mg DNT,\u0026nbsp;the F1 fraction of Cd in sediments decreased\u0026nbsp;from 2.688\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 2.302 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 700\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e. The F2 fraction of Cd decreased\u0026nbsp;from 1.303\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 0.824 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 700\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e. However, the F3 and F4 fractions of Cd maintain relatively constant content of\u0026nbsp;0.580\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e and\u0026nbsp;0.758\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, respectively\u0026nbsp;(Fig. 7(c)).\u0026nbsp;For\u0026nbsp;HA\u0026nbsp;Mw of\u0026nbsp;10\u0026ndash;30 kDa with 200 mg DNT, the F1 fraction decreased from 2.911\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 2.709 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 350\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e, the F2 fraction decreased from 1.263 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 1.104 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e of 350\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e, and\u0026nbsp;the\u0026nbsp;content of the F3 and F4 fractions were\u0026nbsp;approximately\u0026nbsp;0.584\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e and\u0026nbsp;0.756\u0026nbsp;mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, respectively\u003csup\u003e\u0026nbsp;\u003c/sup\u003e(Fig. 7(e)). The total Cd content decreased from 5.316 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e for 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 4.481 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e for 700\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e with 30\u0026ndash;100\u0026nbsp;kDa HA,\u0026nbsp;and was reduced from 5.504 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e for 25\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 5.133 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e for 350\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e with\u0026nbsp;10\u0026ndash;30\u0026nbsp;kDa HA.\u003c/p\u003e\n\u003cp\u003e3.4.3\u0026nbsp;Humic acid\u0026nbsp;molecular weights of\u0026nbsp;1\u0026ndash;10 kDa and \u0026lt;1 kDa\u003c/p\u003e\n\u003cp\u003eAs the UF4 concentration increased from 25 to 175\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e,\u0026nbsp;the content of the F1, F2, F3, and F4 fractions of Cd in sediments were 2.962\u0026ndash;2.887 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, 1.306\u0026ndash;1.264 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, 0.566\u0026ndash;0.548 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, and 0.752\u0026ndash;0.737 mg\u0026middot;kg\u003csup\u003e-1\u003c/sup\u003e, respectively.\u0026nbsp;For HA\u0026nbsp;Mw of\u0026nbsp;\u0026lt;1 kDa,\u0026nbsp;the Cd content and chemical fraction in sediments did not change significantly with the HA concentration.\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 7\u0026gt;\u003c/p\u003e\n\u003cp\u003e3.4.4 Mechanism of interaction between various molecular weight\u0026nbsp;humic acids and dinotefuran\u003c/p\u003e\n\u003cp\u003eBased on the above results, the content of total\u0026nbsp;Cd, F1, and F2 in sediments decreased with increasing concentration of HAs with Mws of \u0026gt;100 kDa,\u0026nbsp;30\u0026ndash;100 kDa, and 30\u0026ndash;10 kDa. At these HA Mws,\u0026nbsp;the\u0026nbsp;F1 fraction\u0026nbsp;of Cd in the sediments remained at ~52.100%, while the\u0026nbsp;F2 fraction\u0026nbsp;of Cd in the sediments decreased\u0026nbsp;with increasing concentration of HAs.\u0026nbsp;In contrast,\u0026nbsp;HA with\u0026nbsp;Mws\u0026nbsp;of\u0026nbsp;1\u0026ndash;10 kDa and\u0026nbsp;\u0026lt;1 kDa in the presence of\u0026nbsp;200 mg DNT\u0026nbsp;did not significantly influence Cd chemical fractionation or total Cd content.\u003c/p\u003e\n\u003cp\u003eFor example, for 75 mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e HA with\u0026nbsp;added DNT,\u0026nbsp;a notable increase in the Cd content in sediments was observed with decreasing HA Mw from \u0026gt;100 kDa to \u0026lt;1 kDa (Fig. 8). Higher Mw HAs have\u0026nbsp;more aromatic components and\u0026nbsp;active adsorption sites; their higher logK (stability constant for complexation between Cd\u003csup\u003e2+\u003c/sup\u003e and humic-like substances)\u0026nbsp;reflects their stronger\u0026nbsp;binding affinity for Cd\u003csup\u003e2+\u003c/sup\u003e (Bai et al.,\u0026nbsp;2018;\u0026nbsp;Gao et al., 2022).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 8\u0026gt;\u003c/p\u003e\n\u003cp\u003eFTIR and\u0026nbsp;three-dimensional fluorescence spectra\u0026nbsp;were used to further investigate the functional groups and interactions in the system. FTIR spectra of the\u0026nbsp;DNT-HA\u0026nbsp;system with various HA Mws are shown in Fig. 9. An N-H stretch at approximately 3300 cm\u003csup\u003e-1\u003c/sup\u003e and C-H stretches at 2877 and 2951 cm\u003csup\u003e-1\u003c/sup\u003e (Maha\u0026nbsp;et al., 2017)\u0026nbsp;were observed in the FTIR spectrum of DNT. Compared with the\u0026nbsp;DNT-HA\u0026nbsp;system, the appearance of the N-H peak at 3300 cm\u003csup\u003e-1\u003c/sup\u003e and C-H peaks at 2877 and 2951 cm\u003csup\u003e-1\u003c/sup\u003e indicates that a hydrogen bonding interaction occurred between DNT and the HAs. The FTIR spectrum of the HAs was characterized by\u0026nbsp;aromatic C=C,\u0026nbsp;COO-,\u0026nbsp;and H-bonded C=O\u0026nbsp;stretches at\u0026nbsp;~1630 cm\u003csup\u003e-1\u003c/sup\u003e (He et al., 2016).\u0026nbsp;The band at ~1400 cm\u003csup\u003e-1\u003c/sup\u003e was\u0026nbsp;assigned to\u0026nbsp;COO- antisymmetric stretching of the HAs\u0026nbsp;(Christl et al., 2000).\u0026nbsp;The\u0026nbsp;DNT-HA\u0026nbsp;spectrum showed a weak shift at the\u0026nbsp;1630 cm\u003csup\u003e-1\u003c/sup\u003e peak and disappearance of the\u0026nbsp;1400 cm\u003csup\u003e-1\u003c/sup\u003e peak, indicating that hydrogen bonding interactions occurred between N-H of DNT and COO- of HA.\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 9\u0026gt;\u003c/p\u003e\n\u003cp\u003eTo further investigate the intensity and positions of the fluorescence peaks,\u0026nbsp;three-dimensional fluorescence spectra\u0026nbsp;(Zhou\u0026nbsp;et al.,\u0026nbsp;2021; Ding\u0026nbsp;et al.,\u0026nbsp;2022)\u0026nbsp;were obtained to characterize the pristine HA mixture and different Mw HAs. Dynamic changes in the structures and compositions of the different Mw HAs interacting with DNT were investigated. Three-dimensional fluorescence spectra of the pristine HA mixture and different Mw HAs (75\u0026nbsp;mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e) with and without addition of DNT (200 mg) at pH 7.0 are shown in Fig. 10. Pristine HA without addition of DNT had a stronger peak intensity at the excitation wavelength (E\u003csub\u003ex\u003c/sub\u003e) of 280 nm and the emission wavelength (E\u003csub\u003em\u003c/sub\u003e) of 485 nm (Fig. 10(a)). The fluorescence intensities of the different MW HAs increased with decreasing Mw, potentially because the lower Mw HAs have higher concentrations of electron-donating groups, such as hydroxyl and methoxyl groups\u0026nbsp;(Gao et al., 2022). Furthermore, the peak positions of different Mw HAs showed a detectable blue-shift with decreasing Mw, reflecting the reduced number of aromatic rings\u0026nbsp;(Ren\u0026nbsp;et al.,\u0026nbsp;2017). This result agreed well with the UV-vis spectra trends.\u003c/p\u003e\n\u003cp\u003eWith the addition of 200 mg DNT (Fig. 10(a\u003csub\u003e1\u003c/sub\u003e\u0026ndash;f\u003csub\u003e1\u003c/sub\u003e)), the three-dimensional fluorescence spectra of\u0026nbsp;HA\u0026nbsp;showed maxima at \u0026lambda;E\u003csub\u003ex\u003c/sub\u003e/\u0026lambda;E\u003csub\u003em\u003c/sub\u003e = 450/520 nm (UF0), \u0026lambda;E\u003csub\u003ex\u003c/sub\u003e/\u0026lambda;E\u003csub\u003em\u003c/sub\u003e = 440/510 nm (UF1), \u0026lambda;E\u003csub\u003ex\u003c/sub\u003e/\u0026lambda;E\u003csub\u003em\u003c/sub\u003e = 440/500 nm (UF2), \u0026lambda;E\u003csub\u003ex\u003c/sub\u003e/\u0026lambda;E\u003csub\u003em\u003c/sub\u003e = 370/450 nm (UF3), \u0026lambda;E\u003csub\u003ex\u003c/sub\u003e/\u0026lambda;E\u003csub\u003em\u003c/sub\u003e = 360/440 nm (UF4), and \u0026lambda;E\u003csub\u003ex\u003c/sub\u003e/\u0026lambda;E\u003csub\u003em\u003c/sub\u003e = 350/400 nm (UF5).\u0026nbsp;The fluorescence\u0026nbsp;intensity\u0026nbsp;of the HAs was quenched by\u0026nbsp;DNT and the peak positions of the\u0026nbsp;HAs showed a red-shift.\u0026nbsp;The decrease in fluorescence and peak shifts indicate that\u0026nbsp;DNT\u0026nbsp;bonding\u0026nbsp;with the HAs\u0026nbsp;induced some micro-environmental changes in the HAs. The modified Stern-Volmer model\u0026nbsp;(Gao\u0026nbsp;et al.,\u0026nbsp;2022)\u0026nbsp;was used to calculate the \u003cem\u003eK\u003c/em\u003e\u003csub\u003eq\u003c/sub\u003e and \u003cem\u003eK\u003csub\u003ea\u003c/sub\u003e\u003c/em\u003e values of HAs binding with\u0026nbsp;DNT (Table 4).\u0026nbsp;These values increased\u0026nbsp;with\u0026nbsp;increasing HA Mw. The relatively high Mw HAs had stronger adsorption affinity and complexing capacity for\u0026nbsp;DNT\u0026nbsp;than the low Mw HAs.\u003c/p\u003e\n\u003cp\u003eFig. 10 (a\u003csub\u003e2\u003c/sub\u003e\u0026ndash;f\u003csub\u003e2\u003c/sub\u003e) displays the three-dimensional fluorescence spectra of\u0026nbsp;HAs\u0026nbsp;with 200 mg DNT after sediment treatment. The fluorescence intensity of DNT and HAs with various Mws was clearly quenched after the treated sediments. The decreased peak intensities and blue-shifted peak positions indicated that electron-donating groups were removed, indicating that the most active fluorophores\u0026nbsp;in the DNT-HA\u0026nbsp;system\u0026nbsp;were binding with Cd from the sediment.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Fig. 10\u0026gt;\u003c/p\u003e\n\u003cp\u003ePlease insert \u0026lt; Table 4\u0026gt;\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eTo investigate the effects of both DNT and HA on mechanisms of Cd migration and transformation in sediments, chemical sequential extraction, UV-vis, EEM, and FTIR techniques were employed to investigate changes in the content and chemical fraction of Cd in sediments. The main findings are as follows:\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eChanges in the DNT dosage mainly affected the content of the F2 fraction of Cd in sediments for DNT dosage from 0.5 to 200 mg and had no effect on the chemical fractions of Cd for DNT dosage \u0026gt;200 mg.\u003c/li\u003e\n \u003cli\u003eHA enhanced migration of Cd from sediment to water, significantly affecting only the F1 chemical fraction of Cd in the sediments. When both DNT and HA were present, the content of total Cd, F1, and F2 noticeably decreased with an increase in the HA concentration from 25 mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e to 273 mg-C\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e; only minor changes in F3 and F4 content were apparent.\u003c/li\u003e\n \u003cli\u003eWhen the pH increased from 5 to 7, total Cd, F1, and F2 content in sediments slightly increased. At pH 8 and 9, the content and chemical fraction of Cd in sediments did not change.\u003c/li\u003e\n \u003cli\u003eIn the presence of DNT and HA, the release rate of Cd from sediments increased with increasing Mw of HA from \u0026lt;1 kDa to \u0026gt;100 kDa. The lower molecular weight of 1\u0026ndash;10 kDa and \u0026lt;1 kDa HAs did not influence the Cd content or chemical fraction. For the higher molecular weight of \u0026gt;100 kDa, 30\u0026ndash;100 kDa, and 10\u0026ndash;30 kDa, the content of total Cd, F1, and F2 decreased with a increase in concentrations of HAs. Therefore, it is important to consider the humic acid with molecular weight greater than 10 kDa in the water environment for the partitioning and transformation of Cd from sediment.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e\u003cem\u003eAuthors Contributions\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBMY (student) has analyzed and interpreted the results. WHB performed the scientific work and was a major contributor in writing the manuscript. LSF contributed to writing the manuscript. YSH read the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eAvailability of data and materials\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article (and its supplementary information files).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eFunding\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis project was supported by the National Key Research and Development Program of China (2017YFD0800301), the National Natural Science Foundation of China (Grant No. 41703129), Liaoning Province Education Administration (No. LJ2020008, LQ2020023, and LJKMZ20220763).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e Not applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e Not applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbdel-Ghany M. 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SAFE, 225, 112811. https://doi.org/10.1016/j.ecoenv.2021.112811.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 Method for determination of chemical fractions of Cd in the sediments\u0026nbsp;(Wang et al., 2022).\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.288732394366196%\" valign=\"top\"\u003e\n \u003cp\u003eFraction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.683098591549296%\" valign=\"top\"\u003e\n \u003cp\u003eExtractant solution\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"38.028169014084504%\" valign=\"top\"\u003e\n \u003cp\u003eExperimental conditions\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.288732394366196%\"\u003e\n \u003cp\u003eF1 Exchangeable/acid soluble fraction (bound to carbonates)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.683098591549296%\"\u003e\n \u003cp\u003e0.11 mol/L HAc (40 mL)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"38.028169014084504%\"\u003e\n \u003cp\u003eShaken for 18 h (22 \u0026plusmn; 2\u0026deg;C); \u0026nbsp;sediment to solution = 1:40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.288732394366196%\"\u003e\n \u003cp\u003eF2 Reducible fraction (bound to Mn and Fe oxides)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.683098591549296%\"\u003e\n \u003cp\u003e40 mL of 0.5 mol/L NH\u003csub\u003e3\u003c/sub\u003eOHCl (adjusted with HNO\u003csub\u003e3\u003c/sub\u003e to pH 2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"38.028169014084504%\"\u003e\n \u003cp\u003eShaken for 18 h (22 \u0026plusmn; 2\u0026deg;C); sediment to solution = 1:40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.288732394366196%\"\u003e\n \u003cp\u003eF3 Oxidizable fraction (bound to organic matter and sulfides)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.683098591549296%\"\u003e\n \u003col\u003e\n \u003cli\u003e8.8 mol/L\u0026nbsp;H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003c/li\u003e\n \u003c/ol\u003e\n \u003cp\u003e2)\u0026nbsp;50 mL of 1 mol/L CH\u003csub\u003e3\u003c/sub\u003eCOONH\u003csub\u003e4\u0026nbsp;\u003c/sub\u003e(adjusted with HNO\u003csub\u003e3\u003c/sub\u003e to pH 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"38.028169014084504%\"\u003e\n \u003cp\u003e1)\u0026nbsp;Heated at 85 \u0026plusmn; 2\u0026deg;C using a water bath for 2 h; sediment to solution = 1:10 (repeat twice);\u003c/p\u003e\n \u003cp\u003e2)\u0026nbsp;Shaken for 18 h (22 \u0026plusmn; 2 \u0026deg;C); sediment to solution = 1:50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"27.288732394366196%\"\u003e\n \u003cp\u003eF4 Residual fraction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.683098591549296%\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"38.028169014084504%\" valign=\"top\"\u003e\n \u003cp\u003eThe total Cd concentration minus F1\u0026ndash;F3; concentrations of F1, F2, and F3 were determined using an atomic absorption spectrophotometer\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 2 Stern-Volmer quenching constants for\u0026nbsp;DNT-HA.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003eEntry\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003eDose (mg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eQ\u003c/em\u003e (mol\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003eq\u003c/sub\u003e (\u0026times;10\u003csup\u003e11\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003ea\u003c/sub\u003e (\u0026times;10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003en\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e1.98\u0026times;10\u003csup\u003e-4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.812\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.427\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e3.96\u0026times;10\u003csup\u003e-4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.743\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.467\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e0.996\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e7.91\u0026times;10\u003csup\u003e-4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.672\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.386\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e1.19\u0026times;10\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.663\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.381\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e0.998\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e1.98\u0026times;10\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.529\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.304\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e2.97\u0026times;10\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.487\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.280\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e3.96\u0026times;10\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.499\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.287\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e4.95\u0026times;10\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.791\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.455\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.908450704225352%\" valign=\"top\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.64788732394366%\" valign=\"top\"\u003e\n \u003cp\u003e5.93\u0026times;10\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.8943661971831%\" valign=\"top\"\u003e\n \u003cp\u003e0.832\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.02112676056338%\" valign=\"top\"\u003e\n \u003cp\u003e0.478\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.619718309859154%\" valign=\"top\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 3 The basic properties of different molecular weight of the humic acid.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"99%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003eTreatment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\"\u003e\n \u003cp\u003eHAs\u003c/p\u003e\n \u003cp\u003e(kDa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003ePercentage (wt.%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003eCarboxyl group\u0026nbsp;(mmol\u0026middot;g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003ePhenolic group\u0026nbsp;(mmol\u0026middot;g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003eTotal acidity\u0026nbsp;(mmol\u0026middot;g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003eDOC (mg\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.541666666666666%\"\u003e\n \u003cp\u003eSUVA\u003csub\u003e280\u003c/sub\u003e\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003e(L\u0026middot;mg C\u003csup\u003e-1\u003c/sup\u003e\u0026middot;m\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003eE\u003csub\u003e2\u003c/sub\u003e:E\u003csub\u003e3\u003c/sub\u003e\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\"\u003e\n \u003cp\u003ePristine HA\u0026nbsp;(UF0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e－\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e32.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e11.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e44.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e273.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.541666666666666%\"\u003e\n \u003cp\u003e10.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e2.45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\"\u003e\n \u003cp\u003e＞100 (UF1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e16.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e33.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e10.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e44.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e1956.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.541666666666666%\"\u003e\n \u003cp\u003e11.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e2.49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\"\u003e\n \u003cp\u003e30-100 (UF2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e13.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e34.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e11.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e46.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e822.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.541666666666666%\"\u003e\n \u003cp\u003e11.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e2.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\"\u003e\n \u003cp\u003e10-30 (UF3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e11.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e36.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e12.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e49.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e481.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.541666666666666%\"\u003e\n \u003cp\u003e10.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e2.79\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\"\u003e\n \u003cp\u003e1-10 (UF4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e9.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e38.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e20.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e59.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e236.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.541666666666666%\"\u003e\n \u003cp\u003e3.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e3.10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\"\u003e\n \u003cp\u003e＜1 (UF5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e48.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e37.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e22.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e60.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\"\u003e\n \u003cp\u003e82.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.541666666666666%\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.333333333333334%\"\u003e\n \u003cp\u003e3.22\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"9\"\u003e\n \u003cp\u003e\u003csup\u003ea\u0026nbsp;\u003c/sup\u003eSpecific ultraviolet (UV) absorbance at 280 nm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"9\"\u003e\n \u003cp\u003e\u003csup\u003eb\u0026nbsp;\u003c/sup\u003eRatio between the specific UV absorbances at 250 and 365 nm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 4 Stern-Volmer quenching constants for the Mw of\u0026nbsp;HAs and DNT.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"99%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003eEntry\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003eMw\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.21212121212121%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003eq\u0026nbsp;\u003c/sub\u003e(\u0026times;10\u003csup\u003e11\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003ea\u0026nbsp;\u003c/sub\u003e(\u0026times;10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003en\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003eUF1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.21212121212121%\" valign=\"top\"\u003e\n \u003cp\u003e0.494\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e0.284\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003eUF2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.21212121212121%\" valign=\"top\"\u003e\n \u003cp\u003e0.623\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e0.358\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e1.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003eUF3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.21212121212121%\" valign=\"top\"\u003e\n \u003cp\u003e0.940\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e0.540\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003eUF4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.21212121212121%\" valign=\"top\"\u003e\n \u003cp\u003e1.300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e0.747\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.161616161616163%\" valign=\"top\"\u003e\n \u003cp\u003eUF5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.21212121212121%\" valign=\"top\"\u003e\n \u003cp\u003e10.300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e5.942\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.232323232323232%\" valign=\"top\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Humic acid, Dinotefuran, Cadmium, Chemical fraction","lastPublishedDoi":"10.21203/rs.3.rs-4127483/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4127483/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe heavy application of dinotefuran (DNT) pesticide in agricultural production and the humic acid (HA) ubiquitous in the aqueous systems have burdened the environment as a new pollutant. The chemical fraction and mobility of cadmium (Cd) in sediments of urban river environments in which DNT and HA coexist are poorly understood. In this study, sequential extraction, ultraviolet-visible spectroscopy (UV-vis), fluorescence excitation-emission matrix (EEM), fourier transform infrared spectrometer (FTIR) techniques, and the Stern-Volmer equationwere integrated to identify the effects of DNT, pH, concentration and molecular weight (Mw) fractions of HA on the content and chemical fraction of Cd in sediments. The DNT dosage strongly affected the Fe–Mn oxide-associated Cd chemical fraction in sediments. HA facilitated migration of Cd from sediments to water. Cd release from sediments was also promoted by a lower pH of 5–6 compared to pH 8–9. Increasing concentrations of higher molecular weight HAs of \u0026gt;100 kDa, 30–100 kDa, and 30–10 kDa reduced total Cd, exchangeable/acid soluble fraction, and reducible fraction content in sediments, while 1–10 kDa and \u0026lt;1 kDa HA did not significantly influence Cd chemical fraction or content. The present study provides new insights into the environmental risks and partitioning of Cd in sediments under co-exposure to DNT and HA.\u003c/p\u003e","manuscriptTitle":"Effects of dinotefuran and humic acid on cadmium migration and transformation in sediments","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-09 08:56:52","doi":"10.21203/rs.3.rs-4127483/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d053e2ee-0e58-4383-aa9f-c410399140ae","owner":[],"postedDate":"May 9th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-12-23T20:03:21+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-09 08:56:52","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4127483","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4127483","identity":"rs-4127483","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}