Speciation and Spatial Distribution of Cyanide and Heavy Metals in Cyanidation Tailings: Implications for Environmental Risk and Management

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Uncertainties surrounding cyanide speciation and migration mechanisms have impeded advancements in safe disposal and resource recovery strategies. This study investigated the physicochemical properties and occurrence patterns of cyanide/heavy metals in typical cyanidation tailings. Key findings include: (1) Multi-phase speciation analysis revealed 73.46% of total cyanide (CN t ) resided in the liquid phase, with free cyanide (CN f ) accounting for 57.65% of CN t , indicating high leaching potential and environmental risk. (2) Spatial profiling within the tailings pond showed CN t concentrations and CN f /CN t ratios increased with depth and decreasing elevation, strongly correlating with moisture content. (3) Heavy metals (Cu, Zn, Pb, Cd, Ni, Mn) were primarily associated with sulfide minerals (pyrite, sphalerite, etc.), existing mainly in residual forms. However, exchangeable fractions significantly increased in mid-deep layers (2.5–8.5 m), while reducible/oxidizable fractions exhibited distinct vertical variations. These results provide critical insights for optimizing tailings management and developing targeted remediation strategies. Cyanide tailings Cyanide Heavy metals Occurrence patterns Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Cyanide tailings are hazardous wastes generated after cyanide extraction of gold in the gold industry and are usually stockpiled in tailings ponds (Frimmel, 2018 ; Faraz et al., 2014 ; Wikedzi et al., 2018 ). Since cyanidation tailings contain toxic components such as cyanides and heavy metals, there are environmental hidden dangers of polluting the environment and endangering the safety and health of human existence in the surroundings of the tailings ponds (Mekuto et al., 2016 ; Donato et al., 2007 ; Korte et al., 2000 ). The selection of suitable methods for the harmless treatment of cyanidation tailings and the identification of directions for their safe and comprehensive utilization are intricately linked to the occurrence states of valuable components and the distribution patterns of pollutants in the tailings (Chen et al., 2020 ; Kyle et al., 2012 ; Roche et al., 2017 ). Currently, driven by the demand for recovering valuable metals such as gold, silver, copper, and iron, numerous domestic and international scholars have extensively investigated the contents and occurrence forms of these metals (Fu et al., 2018 ; Li et al., 2020 ; Dong et al., 2024 ; Kiventerä et al., 2018 ). Nevertheless, research on the distribution patterns of cyanides remains limited. Consequently, cyanide enterprises often struggle to select appropriate treatment methods when dealing with cyanidation tailings. This lack of a solid scientific basis not only undermines the effectiveness of the treatment process but also significantly reduces the practicality and economic viability of the applied technologies. Moreover, the insufficient understanding of how pollutants behave in cyanidation tailings-ncluding their spatial distribution, migration mechanisms, transformation processes, and influencing factors—poses a major challenge to environmental management of tailings ponds. As a result, there is a pressing need for more in-depth research to provide robust scientific guidance for environmental protection efforts in this area. In the realm of heavy metal research, the majority of scholars have predominantly focused on the impact of pollution sources on the surrounding ecological environment. Their studies primarily center on elucidating the distribution characteristics and dynamic patterns of heavy metals in soils and rivers adjacent to tailings ponds. Conversely, the investigation into the distribution of heavy metals within the tailings ponds themselves remains relatively under-explored. For instance, Shu employed geochemical and mineralogical analytical techniques to conduct a meticulous comparative analysis of fresh and weathered tailings derived from the polymetallic sulfide ores of Dabao Mining (Shu al., 2018). Their findings revealed that heavy metals in fresh tailings predominantly existed in the form of sulfides. In contrast, within weathered tailings, these metals were mainly present as silicates. The ecological risk index evaluation further demonstrated that the order of ecological risk posed by these heavy metals was Cd > Cu > Zn > Pb. Similarly, Wang undertook a comprehensive sampling and analysis of the surface soils surrounding the Wunugetushan Copper-Molybdenum Mine (Wang et al., 2018 ). Their research delved into the concentrations and spatial distributions of chromium, nickel, zinc, copper, molybdenum, and cadmium. Significantly, the levels of these six heavy metals, particularly copper and molybdenum, were found to be substantially higher than the local background values. Moreover, the study indicated a decreasing trend in their concentrations as the distance from the mining area increased, strongly suggesting that mining activities played a pivotal role in the dispersion of these pollutants. During the storage of cyanide tailings in tailings ponds, components such as cyanides, sulfides, and heavy metals undergo complex transformations influenced by natural factors. These dynamic changes are intricately linked to the inherent physical-chemical properties of the tailings, including particle size distribution, moisture content, mineralogy, and pollutant speciation. Additionally, they are significantly modulated by external factors such as storage configurations, duration, regional climate, and anthropogenic activities (Xu et al., 2022 ; Dobrosz-Gómez et al., 2017 ; Oudjehani et al., 2002 ; Tran et al., 2019 ). Systematic investigation into the physical-chemical characteristics of cyanide tailings, the occurrence patterns of valuable and hazardous components, and the spatial distribution of pollutants during storage is of paramount importance. Such research not only underpins the development of sustainable utilization strategies, including extraction of valuable elements, underground backfilling, and building material fabrication, but also provides critical technical support for selecting appropriate remediation methods and optimizing treatment processes (Hamberg et al., 2015 ; Niu et al., 2024 ; Hasab et al., 2014 ). Furthermore, by elucidating the migration and transformation mechanisms of pollutants, it enables data-driven decision-making for intelligent management of tailings storage facilities, thereby enhancing operational safety and environmental protection (Kuyucak and Akcil, 2013 ; Jaszczak et al., 2017 ; Teimouri et al., 2020 ; Wang et al., 2019 ). In this study, a representative gold mine tailings storage facility in China, which employs the all-slime cyanidation process, was selected as the sampling and research site. A comprehensive and systematic investigation was carried out on the granulometric composition, chemical composition, mineralogical composition of the cyanide tailings. The distribution patterns and interrelationships among the pH values, moisture contents, and cyanide compounds were meticulously elucidated. Furthermore, the spatial distribution and occurrence states of cyanides within the tailings storage facility were thoroughly explored. By utilizing the modified BCR sequential extraction procedure, the proportions of the exchangeable, reducible, oxidizable, and residual fractions of Cu, Zn, Pb, Cd, Ni, and Mn were precisely determined. These analyses have effectively revealed the occurrence mechanisms of heavy metals in cyanide tailings, providing valuable insights into their environmental behavior and potential ecological impacts. 2. Materials and Methods 2.1 Tailing sample collection A typical tailings storage facility adopting the all-slime cyanidation process in China was selected as the sampling and research area. A systematic grid-based sampling approach was implemented, with nine sampling locations established across the TSF. The inter-point spacing was maintained at approximately 10 meters (Fig. S1 ). Sampling operations were conducted using a drilling rig, with sampling depths set at 0.5, 2.5, 4.5, 6.5 and 8.5 m, corresponding to estimated storage durations of 1, 3, 5, 7, and 9 a, respectively. Upon collection, samples were immediately sealed in polyethylene bags and transported to the laboratory for chemical analysis. Subsamples not immediately analyzed were stored at 4°C in a refrigerated environment for preservation. 2.2 Analysis and calculation methods For each of the 45 cyanide tailings samples, 50 g subsamples were randomly collected, dried to constant weight at 40°C, homogenized by cone splitting, and analyzed via XRF, XRD, and gold phase analysis. The pH value was determined using a pH meter after thorough stirring to achieve uniformity at a solid-liquid ratio of 1:2.5. Total Cyanide (CN t ) includes all simple cyanides (predominantly alkali/alkaline-earth metal cyanides and ammonium cyanide) and most complex cyanides (e.g., zinc, iron, nickel, and copper cyanocomplexes), excluding the cobalt cyanide complex. Free Cyanide (CN f ) encompasses all simple cyanides (mostly alkali/alkaline-earth metal cyanides) and zinc cyanocomplexes, while excluding ferrocyanides, ferricyanides, copper, nickel, and cobalt cyanocomplexes. Difficult-to-release cyanide (CN d ) represents the fraction of CN t that is not included in CN f , comprising ferrocyanides, ferricyanides, copper cyanocomplexes, and nickel cyanocomplexes. CN t and CN f were determined according to the volumetric and spectrophotometric methods specified in Water Quality-Determination of Cyanide (HJ 484–2009) and Soil Quality-Determination of Cyanide (HJ 745–2015). CN d was calculated using Eq. ( 1 ). $$\:{CN}_{d}={CN}_{t}-{CN}_{f}$$ 1 The speciation distribution of heavy metals in the tailings was determined by sequential extraction using the modified BCR method (Table S1 ), followed by quantification via inductively coupled plasma mass spectrometry (ICP-MS). Four operationally defined fractions were analyzed: exchangeable/acid-extractable fraction (EX), reducible fraction (RED), oxidizable fraction (OXI), and residual fraction (RES). The detailed extraction procedure was illustrated in Table S1 . The leaching toxicity test was conducted according to the Solid Waste-Extraction Procedure for Leaching Toxicity-Sulfuric Acid & Nitric Acid Method (HJ/T 299–2007). The leachate was collected and analyzed for subsequent measurements. The experimental data were meticulously analyzed and processed using Excel 2020 and Origin 2018. The experimental outcomes are reported as mean values. Regarding the phase analysis, a single characterization was conducted for each sample, and no replicates were performed. 3. Results and discussion 3.1 Grain size, main elements and mineral composition of cyanide tailings The particle size of this cyanide tailings is relatively fine, and the tailings with a particle size below 0.075 mm account for 75.38% (Table S2). The main chemical components of the tailings are SiO₂, Al₂O₃, Fe₂O₃, CaO, Na₂O, MgO, K₂O, etc., belonging to aluminosilicate tailings. The total sulfur content is 0.43%, and the contents of heavy metals such as Cu, Zn, Pb, Cd, Ni, and Mn are 0.11%, 0.07%, 0.05%, 0.02%, 0.02%, and 0.01% respectively, which mainly come from pyrite, sphalerite, chalcopyrite, and galena (Fig. S2). The analysis results of XRD (Fig. S3) show that the main crystalline substances in the cyanide tailings are quartz, mullite, kaolinite, dickite, chlorite, and vermiculite. Among them, chlorite and vermiculite are layered clay minerals that are prone to slime formation, have a relatively strong adsorption capacity for heavy metals. 3.2 The change trend of pH value in cyanidation tailings. The pH value is one of the important factors affecting the migration and transformation of pollutants in cyanide tailings. Under normal circumstances, cyanide will form hydrogen cyanide and volatilize as the pH value of the tailings decreases, resulting in a decrease in its content. Heavy metals will also dissolve and migrate due to the decrease in pH value. The variation trend of the pH value at different sampling points in the cyanide tailings (Fig. 1 ) shows that the pH value generally remains between 7.5 and 10. The pH value of the samples at the surface sampling points is significantly lower than that of the samples at the deep sampling points, and as the sampling depth increases, the pH value generally shows an increasing trend. Below 4.5 meters, the increasing trend slows down or remains stable. This is mainly because the surface samples are vulnerable to factors such as wind, sunlight, and precipitation in the natural environment. Pyrite is prone to oxidation, and the alkaline substances in the tailings migrate with rainwater and other behaviors, resulting in a decrease in pH. However, the pH value of each sampling point of the surface tailings still remains between 7.5 and 9. 3.3 The distribution and occurrence forms of cyanide in tailings After cyanide enters the tailings pond for storage along with the tailings, under the influence of wind, sunlight, precipitation, microorganisms, and human activities in the natural environment, a series of migration and transformation behaviors such as volatilization, oxidation, hydrolysis, complexation, complex precipitation, and biological transformation occur, resulting in changes in the spatial distribution of the cyanide content in the tailings pond. The spatial distribution of the cyanide content (Fig. S4) shows that the overall cyanide content is lower at the top and higher at the bottom, and lower near the source and higher further away. According to the sampling points, the cyanide content in the tailings at sampling points 1#-5# is generally lower than that at sampling points 6#-9#. Among them, the cyanide content in the tailings at sampling point 1# is the lowest, and the cyanide content in the tailings at sampling point 9# is the highest. This is related to the location characteristics of the sampling points and the water content (Fig. 1 ). The terrain at sampling point 1# is the highest, and the terrain at sampling point 9# is the lowest. The change trend of the cyanide content is basically consistent with that of the water content because the CN bond in cyanide is a covalent bond with strong polarity, which is extremely soluble in water and prone to migration with the water flow. From the variation trend of the cyanide content in the tailings and their toxic leachates at different sampling points (Fig. 2 ), it can be seen that the cyanide content generally shows a trend of gradually increasing with the increase of the sampling depth. This is because the surface tailings are prone to air drying, precipitation scouring, oxidation and other effects, resulting in a relatively large decrease in the cyanide content in the tailings. The cyanide content in the middle and deep tailings at sampling points 7#-9# is relatively high. This is because the terrain at sampling points 7#-9# is relatively low, the water content in the tailings is relatively high, the middle and deep tailings are well sealed, and the amount of natural degradation of cyanide is relatively small. In addition, the variation trend of the cyanide content in the toxic leachates of the tailings with the sampling depth is basically consistent with the change of the cyanide content in the tailings, indicating that the cyanide in the tailings can be dissolved during water immersion and migrate with precipitation. In addition, the variation trend of the proportion of CN f to CN t in the tailings at different sampling points (Fig. 3 ) shows that the overall CN f /CN t increases with the increase of the sampling depth. The CN f /CN t in the tailings at sampling points 7#-9# is higher than that at other sampling points. The main reason is that the natural degradation of cyanide in the surface tailings is relatively severe, and the degradation mainly occurs in the form of CN f , resulting in a lower CN f /CN t . At sampling points 7#-9#, due to the relatively slow natural degradation, the decrease in the CN f content is relatively small, and the CN f /CN t remains relatively high. 3.4 The distribution and occurrence forms of heavy metals in tailings The tailings from sampling points 2#, 5#, and 8# in the middle of the tailings pond were selected as the experimental objects. Heavy metals with high contents in the tailings, including Cu, Zn, Pb, Cd, Ni, and Mn, were chosen as pollution factors to analyze the changes in heavy metal speciation at different sampling depths. The speciation distribution of Cu in tailings at different depths of each sampling point (Fig. 4 ) shows that the residual Cu accounts for approximately 45–60% in the middle-deep layer samples, while it accounts for 81–83% in the surface samples. The exchangeable Cu accounts for 16–33% in the middle-deep layer samples and 3–10% in the surface samples. The proportions of reducible Cu and oxidizable Cu are both reduced to varying degrees in the surface tailings, indicating that a large amount of Cu in the surface tailings is released and migrated, and another part undergoes redox reactions and is eroded, thereby being released. Since Cu mainly exists in chalcopyrite, it is relatively easy to be oxidized and decomposed in the natural environment. The horizontal distribution of Cu speciation from sampling point 2# to 8# shows that the proportion of exchangeable Cu generally increases gradually, while the proportion of residual Cu decreases gradually, suggesting that the released exchangeable Cu migrates to low-lying areas with water flow. The distribution of the four speciations of Zn in tailings at different depths of each sampling point (Fig. 5 ) is relatively dispersed. The surface layer is dominated by residual Zn, while the middle-deep layer is mostly composed of exchangeable Zn. The proportions of reducible and oxidizable Zn show very small variation ranges with the increase of sampling depth. This is because Zn in the tailings mainly exists in sphalerite, which is relatively stable in the natural environment and hardly undergoes redox reactions. Exchangeable species generally refer to water-soluble, exchangeable heavy metals combined with carbonates, which are mainly adsorbed on the surface of tailings or exist in the form of hydroxides and carbonates. The lower content of exchangeable Zn in surface tailings is due to the vertical and horizontal migration of exchangeable Zn with precipitation to deeper layers and low-lying areas, which is reflected by the increase in the proportion of exchangeable Zn in middle-deep tailings samples and tailings samples from sampling points 5# and 8#. The morphological distribution of Pb in tailings at different depths of each sampling point (Fig. 6 ) is dominated by the residual form, accounting for approximately 55%-66%. The exchangeable form comes second, accounting for about 22%-30%. The proportions of the reducible form (5%-10%) and the oxidizable form (5%-14%) are the smallest. Analysis of the morphology of Pb in tailings samples at different depths shows that the proportion of the residual form of Pb is the largest at a depth of 0.5 m, with relatively less distribution of the other three forms, and the oxidizable form has the least distribution. This is because the surface-layer tailings are most affected by the natural environment, being prone to oxidation, erosion, and hydrolysis, resulting in the transformation of oxidizable Pb into the exchangeable and residual forms. The morphology of Pb in tailings at depths from 2.5 m to 8.5 m shows an irregular distribution. A comparative analysis of the morphology of Pb in tailings samples at the same depth in each sampling point reveals that from sampling point 2# to 8#, the proportion of exchangeable Pb in tailings samples at depths of 0.5 m and 2.5 m gradually increases. This is because the terrain from sampling point 2# to 8# gradually descends, and exchangeable Pb migrates downward with water flow, leading to an increase in the content of exchangeable Pb in tailings at lower-lying areas. Tailings at depths from 4.5 m to 8.5 m are less disturbed by the outside world, and the morphology of Pb basically maintains its original distribution with small-scale irregular fluctuations. In the morphological distribution of Cd in tailings at different depths of each sampling point (Fig. 7 ), the residual form dominates overall, with a proportion ranging from 58–79%. It is particularly high in surface layer tailings samples, accounting for 77%-79%. The distributions of the other three forms are relatively dispersed, with the lowest proportions in the surface layer. Analysis of the morphological distribution of Cd in tailings at the same depth but different sampling points shows that from sampling point 2# to 8#, as the terrain descends, except that the proportion of exchangeable Cd in tailings samples generally increases slightly, the other three forms basically fluctuate slightly and irregularly. This indicates that, apart from the vertical and horizontal migration of exchangeable Cd adsorbed on the surface of tailings, the other forms of Cd remain relatively stable. This is because Cd mainly exists in silicate minerals, which is relatively stable. In the morphological distribution of Ni in tailings at different depths of each sampling point (Fig. 8 ), the residual form dominates overall, with a proportion ranging from 54–76%. The exchangeable form comes second, accounting for 13%-25%, while the reducible and oxidizable forms have the smallest proportions, ranging from 4%-14% and 4%-17% respectively. The proportion of the residual form of Ni in surface layer tailings is 12%-20% higher than that in middle and deep layer tailings, while the proportions of the other three forms are lower. This is mainly because, affected by natural conditions such as oxidation, weathering, and precipitation induced erosion, the exchangeable Ni in surface layer tailings has migrated. This also indicates that Ni is mainly adsorbed on the surface of tailings or exists in minerals such as pyrite that are prone to erosion and decomposition. A comparative analysis of the morphology of Ni in tailings samples at the same depth across different sampling points shows that from sampling point 2# to 8#, the proportion of exchangeable Ni in tailings samples generally shows an increasing trend. This indicates that as the terrain of the sampling points lowers, exchangeable Ni migrates downward with water flow, resulting in an increase in the content of exchangeable Ni in tailings at lower lying areas. In the morphological distribution of Mn in tailings at different depths of each sampling point (Fig. 9 ), the residual form also predominates, accounting for 40–60%, with the other three forms distributing relatively evenly. The proportion of residual Mn is higher in surface tailings samples, while the proportion of oxidizable Mn is lower, indicating that Mn-associated minerals in the surface tailings, such as pyrite and chalcopyrite, are oxidatively decomposed. Part of Mn is converted into the exchangeable form and migrates with water flow, leading to an increase in the proportion of exchangeable Mn in surface tailings at low-lying areas (evident by the significant increase in exchangeable Mn proportion in tailings at 2.5 m depth), while another part exists as residual form in silicate minerals. Additionally, the morphology of Mn remains relatively stable at depths of 4.5–8.5 m across all sampling points, suggesting limited vertical migration of Mn in the middle-deep layers. 3.5 Environmental risk and management insights from cyanidation tailings studies These findings provide guidance for the environmental risk assessment and management of cyanide tailings. For risk evaluation, prioritize monitoring free cyanide in liquids 57.65% of total cyanide, with 73.46% in liquid phase over total cyanide alone, as CN f directly indicates leaching/toxicity risks. Spatial heterogeneity, with higher CN t , CN f /CN t ratios, and moisture in deeper, lower zones, demands stratified/zoned sampling to identify hotspots. For heavy metals, though residual fractions dominate, increased exchangeable forms in 2.5–8.5 m layers and vertical variations in reducible/oxidizable fractions signal potential activation, requiring long-term bioavailability checks. Management should target liquid cyanide via in-situ fixation and moisture control (e.g., liners). Stratified approaches are key: stabilize/extract deep high moisture zones; cap surfaces to prevent infiltration. Tailor heavy metal remediation use adsorbents for exchangeable fractions, control redox for reducible/oxidizable forms. Shift to precision governance with dynamic monitoring of cyanide speciation, metal fractions, and moisture to minimize risks. 4. Conclusions This study systematically elucidated the occurrence mechanisms of cyanide and heavy metals in cyanidation tailings. By comprehensively analyzing the content and speciation of CN t , CN f and CN d across multiphase media (pulp, filtrate, and tailings solids), it was determined that 73.46% of the cyanide resides in the liquid phase of the tailings, with CN f accounting for 57.65% of the total. These findings underscore the predominant liquid-phase distribution of cyanide and its associated elevated environmental risk. Spatial sampling across the tailings impoundment revealed a significant increase in CN t content and the CN f /CN t ratio with increasing depth and decreasing elevation, demonstrating a strong positive correlation with water content. Heavy metals, including Cu, Zn, Pb, Cd, Ni, and Mn, are predominantly hosted within sulfide minerals such as pyrite, sphalerite, chalcopyrite, and galena. While these metals are mainly present in residual forms overall, the proportion of exchangeable fractions notably increases in the middle deep strata (2.5–8.5 m). Moreover, the reducible and oxidizable fractions of Cu, Pb, Ni, and Mn exhibit distinct vertical differentiation patterns, indicating complex geochemical processes within the tailings matrix. Declarations Acknowledgements This research was funded by the National Natural Science Foundation of China (42277004) and the National Key Research and Development Program of China (2022YFC3702104). Declaration of interest statement The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding This research was funded by the National Natural Science Foundation of China (42277004) and the National Key Research and Development Program of China (2022YFC3702104). Authors’ Contributions Qiang Liu: Conceptualization, methodology, investigation, formal analysis, manuscript writing. Jiyan Shi: Conceptualization, funding acquisition, review & editing. Consent to Participate All participants agree to participate in the study, understand the purpose, risks, and benefits of the study, and also agree to abide by all the regulations and conditions of the study. Consent to Publish This manuscript has not been published or presented elsewhere in part or in entirety, and is not under consideration by another journal. All the authors have approved the manuscript and agree with submission to your esteemed journal. Competing Interests The authors declare no competing interests. Data Availability Statement The data used in this research are available from the corresponding author upon reasonable request. Ethical Approval This study did not involve human or animal subjects, so ethical approval was not applicable. References Chen, Y., Song, Y.H., Chen, Y., Zhang, X.W., Lan, X.Z., 2020. Comparative experimental study on the harmless treatment of cyanide tailings through slurry electrolysis. Sep. Purif. Technol. 251, 117314. Dobrosz-Gómez, I., García, B.D.R., GilPavas, E., García, M.Á.G., 2017. Kinetic study on HCN volatilization in gold leaching tailing ponds. Miner. Eng. 110, 185–194. Donato, D.B., Nichols, O., Possingham, H., Moore, M., Ricci, P.F., Noller, B.N., 2007. A critical review of the effects of gold cyanide-bearing tailings solutions on wildlife. Environ. Int. 33, 974–984. Dong P., Song Y.H., Wu L., Bao J., Yin N., Zhu R.Y., Li Y.F., Li H.F., 2024. Efficient recovery of iron from anaerobic roasted cyanide tailings using advanced oxidation technology. Hydrometallurgy. 224, 106241. Faraz, S., Hossna, D., Rezgar, B., Piroz, Z., 2014. Improved recovery of a low-grade refractory gold ore using flotation–preoxidation–cyanidation methods. Int. J. Min. Sci. Tec. 24, 537–542. Frimmel, H.E., 2018. Episodic concentration of gold to ore grade through Earth's history. Earth-sci. Rev. 180, 148–158. Fu P.F., Li Z.Y., Feng J., Bian Z.Z., 2018. Recovery of Gold and Iron from Cyanide Tailings with a Combined Direct Reduction Roasting and Leaching Process. Metals. 8, 561. Hamberg, R., Maurice, C. and Alakangas, L., 2015. Use of cemented paste backfill based on arsenic–rich tailings from cyanidation. In International Conference on Acid Rock Drainage and IMWA Annual conference. Hasab, M.G., Rashchi, F., Raygan, S., 2014. Chloride–hypochlorite leaching and hydrochloric acid washing in multi-stages for extraction of gold from a refractory concentrate. Hydrometallurgy. 142, 56–59. Jaszczak, E., Polkowska, Z., Narkowicz, S., Namiesnik, J., 2017. Cyanides in the environment-analysis-problems and challenges. Environ. Sci. Pollut. Control Ser. 24, 15929–15948. Kiventerä, J., Lancellotti, I., Catauro, M., Poggetto, F.D., Leonelli, C., Illikainen, M., 2018. Alkali activation as new option for gold mine tailings inertization. J. Clean. Prod. 187, 76–84. Korte, F., Spiteller, M., Coulston, F., 2000. The cyanide leaching gold recovery process is a non-sustainable technology with unacceptable impacts on ecosystems and humans: The disaster in Romania. Ecotox. Environ. Safe. 46, 241–245. Kuyucak, N., Akcil, A., 2013. Cyanide and removal options from effluents in gold mining and metallurgical processes. Miner. Eng. 50–51, 13–29. Kyle, J.H., Breuer, P.L., Bunney, K.G., Pleysier, R., 2012. Review of trace toxic elements (Pb, Cd, Hg, As, Sb, Bi, Se, Te) and their deportment in gold processing: Part II: deportment in gold ore processing by cyanidation. Hydrometallurgy. 111, 10–21. Li H.Y., Long H.L., Zhang L.B., Yin S.H., Li S.W., Zhu F., Xie H.M., 2020. Effectiveness of microwave-assisted thermal treatment in the extraction of gold in cyanide tailings. J. Hazard. Mater. 384, 121456. Mekuto, L., Ntwampe, S.K.O., Akcil, A., 2016. An integrated biological approach for treatment of cyanida-tion wastewater. Sci. Total. Environ. 571, 711–720. Niu, M.X., Ge, X.X., Dai, Y.G., Jin, X., Sun, W.W., Hu, X.L., 2024. Effects of sintering parameters on the preparation and properties of foamed ceramics from cyanide tailings. J. Asian. Ceram. Soc. 1–13. Oudjehani, K., Zagury, G. and Deschênes, L., 2002. Natural attenuation potential of cyanide via microbial activity in mine tailings. Appl. Microbiol. Biotechnol. 58, 409–415. Roche, C., Thygesen, K., Baker, E., 2017. Mine tailings storage: safety is no accident. a UNEP rapid response assessment. United Nations Environment Programme. New York, US: Springer. Shu, X.H., Zhang, Q., Lu, G.N., Yi, X.Y., Dang, Z., 2018. Pollution characteristics and assessment of sulfide tailings from the Dabaoshan Mine, China. Int. Biodeter. Biodegr. 128, 122–128. Teimouri, S., Potgieter, J.H., Simate, G.S., Van Dyk, L., Dworzanowski, M., 2020. Oxidative leaching of refractory sulphidic gold tailings with an ionic liquid. Miner. Eng. 156, 106484. Tran, Q.B., Lohitnavy, M., Phenrat, T., 2019. Assessing potential hydrogen cyanide exposure from cyanide-contaminated mine tailing management practices in Thailand’s gold mining. J. Environ. Manag. 249, 109357. Wang, J., Wang, W., Dong, K., Fu, Y., Xie, F., 2019. Research on leaching of carbonaceous gold ore with copper-ammonia-thiosulfate solutions. Miner. Eng. 137, 232–240. Wang, Z.Q., Hong, C., Xing, Y., Wang, K., Li, Y.F., Feng, L.H., Ma, S.L., 2018. Spatial distribution and sources of heavy metals in natural pasture soil around copper-molybdenum mine in Northeast China. Ecotox. Environ. Safe. 154, 329–336. Wikedzi, A., Arinanda, M.A., Leißner, T., Peuker, U.A., Mütze, T., 2018. Breakage and liberation characteris-tics of low grade sulphide gold ore blends. Miner. Eng. 115, 33–40. Xu, Y., Li, W.Y., Liu, Y.Q., Liu, J.C., Li, L., Yan, D.H., 2022. Long-term degradation characteristics of cyanide in closed monofills and its effects on the environment and human health: Evidence from nine landfill sites in northen China. Sci. Total. Environ. 839, 156269. Additional Declarations No competing interests reported. Supplementary Files Supplymentarymaterials.doc 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. 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Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0klEQVRIiWNgGAWjYBACPmYgkQDE/PKPDxz48IMILWwwLZINaYkHZ/YQowXGMDiQY3yYgw2fWpgWdh7DGw9q7tg1HDjz4TADD4M8v9gBQg7jMbZIOPYsubGxd8PhAgsGw5mzEwhqMZNIYDuczMzMu+HwDB6GBIPbRGn5dziZjY3nwWEeNmK1JLYdtuPh4WEgVgtbsUVi3+EECQk2A2AgSxD2Cz//4Y03f3w7bG9/g/nxhw8/bOT5pQloAQEJIE5sQLCJACBl9sQpHQWjYBSMghEJAJBTQKkuDZxsAAAAAElFTkSuQmCC","orcid":"","institution":"Zhejiang University","correspondingAuthor":true,"prefix":"","firstName":"Qiang","middleName":"","lastName":"Liu","suffix":""},{"id":512476363,"identity":"9b36213a-bf2c-44fb-9aa5-ede9d7616b6e","order_by":1,"name":"Jiyan Shi","email":"","orcid":"","institution":"Zhejiang University","correspondingAuthor":false,"prefix":"","firstName":"Jiyan","middleName":"","lastName":"Shi","suffix":""}],"badges":[],"createdAt":"2025-08-16 12:38:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7387467/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7387467/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":91011388,"identity":"4115fb9a-1e6a-4ad1-9193-4012c2f9e30a","added_by":"auto","created_at":"2025-09-10 15:49:55","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":255227,"visible":true,"origin":"","legend":"\u003cp\u003eChanges in pH moisture and content of tailings with sampling depth at different sampling sites\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/333a12d4994b66693d469766.png"},{"id":91012244,"identity":"22947824-7509-46a8-8b7e-87df1e4abe69","added_by":"auto","created_at":"2025-09-10 15:57:55","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":269992,"visible":true,"origin":"","legend":"\u003cp\u003eThe variation of cyanide content in tailings and their toxic leachates at different sampling points with the sampling depth\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/714caa636e66e53f9372d17f.png"},{"id":91011391,"identity":"d0e3f7de-2353-4881-9f9d-cc7d795b80a1","added_by":"auto","created_at":"2025-09-10 15:49:55","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":135909,"visible":true,"origin":"","legend":"\u003cp\u003eThe proportion of CN\u003csub\u003ef\u003c/sub\u003e to CN\u003csub\u003et\u003c/sub\u003e in tailings at different sampling sites varies with sampling depth\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/cd972c36615c9ea375158ef5.png"},{"id":91012803,"identity":"737d9a5d-e915-4e64-9182-657cadb76e76","added_by":"auto","created_at":"2025-09-10 16:05:55","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":394458,"visible":true,"origin":"","legend":"\u003cp\u003eThe proportion of Cu speciation in tailings samples at different sampling sites and depths\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/cc3dbc4b2191b985efff65fa.png"},{"id":91012248,"identity":"84952f55-dcb5-422b-88fc-7edfba70afe1","added_by":"auto","created_at":"2025-09-10 15:57:56","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":392116,"visible":true,"origin":"","legend":"\u003cp\u003eThe proportion of Zn speciation in tailings samples at different sampling sites and depths\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/668acb8711c900f17ec1073a.png"},{"id":91013771,"identity":"54ebb218-01e7-4dbc-921a-7930623c3142","added_by":"auto","created_at":"2025-09-10 16:13:56","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":380991,"visible":true,"origin":"","legend":"\u003cp\u003eThe proportion of Pb speciation in tailings samples at different sampling sites and depths\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/b435aaa8eb4bc1156650407e.png"},{"id":91011404,"identity":"2cc71a2e-9811-41db-baf6-ba689c6a6a9a","added_by":"auto","created_at":"2025-09-10 15:49:56","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":394397,"visible":true,"origin":"","legend":"\u003cp\u003eThe proportion of Cd speciation in tailings samples at different sampling sites and depths\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/fc9144374178413a0d079499.png"},{"id":91012246,"identity":"57c24982-6304-4882-a920-be0651793c6d","added_by":"auto","created_at":"2025-09-10 15:57:56","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":376540,"visible":true,"origin":"","legend":"\u003cp\u003eThe proportion of Ni speciation in tailings samples at different sampling sites and depths\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/35447d8ab6a2b675f65960d0.png"},{"id":91011403,"identity":"5dd7a691-6cd4-4d61-94f3-e2af904e4986","added_by":"auto","created_at":"2025-09-10 15:49:56","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":397645,"visible":true,"origin":"","legend":"\u003cp\u003eThe proportion of Mn speciation in tailings samples at different sampling sites and depths\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/c4cbc01c84c3fc9e598c7a79.png"},{"id":94987563,"identity":"d3271d58-d258-458e-9a8a-cdf985ea7a8d","added_by":"auto","created_at":"2025-11-03 07:02:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3654536,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/7554e6ea-04ad-415e-a55c-bb0a2b822ae6.pdf"},{"id":91011390,"identity":"616f236a-4885-4c56-a7d5-b27e692238b6","added_by":"auto","created_at":"2025-09-10 15:49:55","extension":"doc","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":1485312,"visible":true,"origin":"","legend":"","description":"","filename":"Supplymentarymaterials.doc","url":"https://assets-eu.researchsquare.com/files/rs-7387467/v1/3af57be7b616419c65e4ba01.doc"}],"financialInterests":"No competing interests reported.","formattedTitle":"Speciation and Spatial Distribution of Cyanide and Heavy Metals in Cyanidation Tailings: Implications for Environmental Risk and Management","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCyanide tailings are hazardous wastes generated after cyanide extraction of gold in the gold industry and are usually stockpiled in tailings ponds (Frimmel, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Faraz et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Wikedzi et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Since cyanidation tailings contain toxic components such as cyanides and heavy metals, there are environmental hidden dangers of polluting the environment and endangering the safety and health of human existence in the surroundings of the tailings ponds (Mekuto et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Donato et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Korte et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2000\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe selection of suitable methods for the harmless treatment of cyanidation tailings and the identification of directions for their safe and comprehensive utilization are intricately linked to the occurrence states of valuable components and the distribution patterns of pollutants in the tailings (Chen et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Kyle et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Roche et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Currently, driven by the demand for recovering valuable metals such as gold, silver, copper, and iron, numerous domestic and international scholars have extensively investigated the contents and occurrence forms of these metals (Fu et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Dong et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Kiventer\u0026auml; et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Nevertheless, research on the distribution patterns of cyanides remains limited. Consequently, cyanide enterprises often struggle to select appropriate treatment methods when dealing with cyanidation tailings. This lack of a solid scientific basis not only undermines the effectiveness of the treatment process but also significantly reduces the practicality and economic viability of the applied technologies.\u003c/p\u003e\u003cp\u003eMoreover, the insufficient understanding of how pollutants behave in cyanidation tailings-ncluding their spatial distribution, migration mechanisms, transformation processes, and influencing factors\u0026mdash;poses a major challenge to environmental management of tailings ponds. As a result, there is a pressing need for more in-depth research to provide robust scientific guidance for environmental protection efforts in this area.\u003c/p\u003e\u003cp\u003eIn the realm of heavy metal research, the majority of scholars have predominantly focused on the impact of pollution sources on the surrounding ecological environment. Their studies primarily center on elucidating the distribution characteristics and dynamic patterns of heavy metals in soils and rivers adjacent to tailings ponds. Conversely, the investigation into the distribution of heavy metals within the tailings ponds themselves remains relatively under-explored. For instance, Shu employed geochemical and mineralogical analytical techniques to conduct a meticulous comparative analysis of fresh and weathered tailings derived from the polymetallic sulfide ores of Dabao Mining (Shu al., 2018). Their findings revealed that heavy metals in fresh tailings predominantly existed in the form of sulfides. In contrast, within weathered tailings, these metals were mainly present as silicates. The ecological risk index evaluation further demonstrated that the order of ecological risk posed by these heavy metals was Cd\u0026thinsp;\u0026gt;\u0026thinsp;Cu\u0026thinsp;\u0026gt;\u0026thinsp;Zn\u0026thinsp;\u0026gt;\u0026thinsp;Pb.\u003c/p\u003e\u003cp\u003eSimilarly, Wang undertook a comprehensive sampling and analysis of the surface soils surrounding the Wunugetushan Copper-Molybdenum Mine (Wang et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Their research delved into the concentrations and spatial distributions of chromium, nickel, zinc, copper, molybdenum, and cadmium. Significantly, the levels of these six heavy metals, particularly copper and molybdenum, were found to be substantially higher than the local background values. Moreover, the study indicated a decreasing trend in their concentrations as the distance from the mining area increased, strongly suggesting that mining activities played a pivotal role in the dispersion of these pollutants.\u003c/p\u003e\u003cp\u003eDuring the storage of cyanide tailings in tailings ponds, components such as cyanides, sulfides, and heavy metals undergo complex transformations influenced by natural factors. These dynamic changes are intricately linked to the inherent physical-chemical properties of the tailings, including particle size distribution, moisture content, mineralogy, and pollutant speciation. Additionally, they are significantly modulated by external factors such as storage configurations, duration, regional climate, and anthropogenic activities (Xu et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Dobrosz-G\u0026oacute;mez et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Oudjehani et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Tran et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eSystematic investigation into the physical-chemical characteristics of cyanide tailings, the occurrence patterns of valuable and hazardous components, and the spatial distribution of pollutants during storage is of paramount importance. Such research not only underpins the development of sustainable utilization strategies, including extraction of valuable elements, underground backfilling, and building material fabrication, but also provides critical technical support for selecting appropriate remediation methods and optimizing treatment processes (Hamberg et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Niu et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Hasab et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Furthermore, by elucidating the migration and transformation mechanisms of pollutants, it enables data-driven decision-making for intelligent management of tailings storage facilities, thereby enhancing operational safety and environmental protection (Kuyucak and Akcil, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Jaszczak et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Teimouri et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn this study, a representative gold mine tailings storage facility in China, which employs the all-slime cyanidation process, was selected as the sampling and research site. A comprehensive and systematic investigation was carried out on the granulometric composition, chemical composition, mineralogical composition of the cyanide tailings. The distribution patterns and interrelationships among the pH values, moisture contents, and cyanide compounds were meticulously elucidated. Furthermore, the spatial distribution and occurrence states of cyanides within the tailings storage facility were thoroughly explored. By utilizing the modified BCR sequential extraction procedure, the proportions of the exchangeable, reducible, oxidizable, and residual fractions of Cu, Zn, Pb, Cd, Ni, and Mn were precisely determined. These analyses have effectively revealed the occurrence mechanisms of heavy metals in cyanide tailings, providing valuable insights into their environmental behavior and potential ecological impacts.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Tailing sample collection\u003c/h2\u003e\u003cp\u003eA typical tailings storage facility adopting the all-slime cyanidation process in China was selected as the sampling and research area. A systematic grid-based sampling approach was implemented, with nine sampling locations established across the TSF. The inter-point spacing was maintained at approximately 10 meters (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Sampling operations were conducted using a drilling rig, with sampling depths set at 0.5, 2.5, 4.5, 6.5 and 8.5 m, corresponding to estimated storage durations of 1, 3, 5, 7, and 9 a, respectively. Upon collection, samples were immediately sealed in polyethylene bags and transported to the laboratory for chemical analysis. Subsamples not immediately analyzed were stored at 4\u0026deg;C in a refrigerated environment for preservation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Analysis and calculation methods\u003c/h2\u003e\u003cp\u003eFor each of the 45 cyanide tailings samples, 50 g subsamples were randomly collected, dried to constant weight at 40\u0026deg;C, homogenized by cone splitting, and analyzed via XRF, XRD, and gold phase analysis. The pH value was determined using a pH meter after thorough stirring to achieve uniformity at a solid-liquid ratio of 1:2.5.\u003c/p\u003e\u003cp\u003eTotal Cyanide (CN\u003csub\u003et\u003c/sub\u003e) includes all simple cyanides (predominantly alkali/alkaline-earth metal cyanides and ammonium cyanide) and most complex cyanides (e.g., zinc, iron, nickel, and copper cyanocomplexes), excluding the cobalt cyanide complex. Free Cyanide (CN\u003csub\u003ef\u003c/sub\u003e) encompasses all simple cyanides (mostly alkali/alkaline-earth metal cyanides) and zinc cyanocomplexes, while excluding ferrocyanides, ferricyanides, copper, nickel, and cobalt cyanocomplexes. Difficult-to-release cyanide (CN\u003csub\u003ed\u003c/sub\u003e) represents the fraction of CN\u003csub\u003et\u003c/sub\u003e that is not included in CN\u003csub\u003ef\u003c/sub\u003e, comprising ferrocyanides, ferricyanides, copper cyanocomplexes, and nickel cyanocomplexes. CN\u003csub\u003et\u003c/sub\u003e and CN\u003csub\u003ef\u003c/sub\u003e were determined according to the volumetric and spectrophotometric methods specified in \u003cem\u003eWater Quality-Determination of Cyanide\u003c/em\u003e (HJ 484\u0026ndash;2009) and \u003cem\u003eSoil Quality-Determination of Cyanide\u003c/em\u003e (HJ 745\u0026ndash;2015). CN\u003csub\u003ed\u003c/sub\u003e was calculated using Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{CN}_{d}={CN}_{t}-{CN}_{f}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe speciation distribution of heavy metals in the tailings was determined by sequential extraction using the modified BCR method (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), followed by quantification via inductively coupled plasma mass spectrometry (ICP-MS). Four operationally defined fractions were analyzed: exchangeable/acid-extractable fraction (EX), reducible fraction (RED), oxidizable fraction (OXI), and residual fraction (RES). The detailed extraction procedure was illustrated in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e. The leaching toxicity test was conducted according to the \u003cem\u003eSolid Waste-Extraction Procedure for Leaching Toxicity-Sulfuric Acid \u0026amp; Nitric Acid Method\u003c/em\u003e (HJ/T 299\u0026ndash;2007). The leachate was collected and analyzed for subsequent measurements.\u003c/p\u003e\u003cp\u003eThe experimental data were meticulously analyzed and processed using Excel 2020 and Origin 2018. The experimental outcomes are reported as mean values. Regarding the phase analysis, a single characterization was conducted for each sample, and no replicates were performed.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Grain size, main elements and mineral composition of cyanide tailings\u003c/h2\u003e\u003cp\u003eThe particle size of this cyanide tailings is relatively fine, and the tailings with a particle size below 0.075 mm account for 75.38% (Table S2). The main chemical components of the tailings are SiO₂, Al₂O₃, Fe₂O₃, CaO, Na₂O, MgO, K₂O, etc., belonging to aluminosilicate tailings. The total sulfur content is 0.43%, and the contents of heavy metals such as Cu, Zn, Pb, Cd, Ni, and Mn are 0.11%, 0.07%, 0.05%, 0.02%, 0.02%, and 0.01% respectively, which mainly come from pyrite, sphalerite, chalcopyrite, and galena (Fig. S2). The analysis results of XRD (Fig. S3) show that the main crystalline substances in the cyanide tailings are quartz, mullite, kaolinite, dickite, chlorite, and vermiculite. Among them, chlorite and vermiculite are layered clay minerals that are prone to slime formation, have a relatively strong adsorption capacity for heavy metals.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.2 The change trend of pH value in cyanidation tailings.\u003c/h2\u003e\u003cp\u003eThe pH value is one of the important factors affecting the migration and transformation of pollutants in cyanide tailings. Under normal circumstances, cyanide will form hydrogen cyanide and volatilize as the pH value of the tailings decreases, resulting in a decrease in its content. Heavy metals will also dissolve and migrate due to the decrease in pH value. The variation trend of the pH value at different sampling points in the cyanide tailings (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) shows that the pH value generally remains between 7.5 and 10. The pH value of the samples at the surface sampling points is significantly lower than that of the samples at the deep sampling points, and as the sampling depth increases, the pH value generally shows an increasing trend. Below 4.5 meters, the increasing trend slows down or remains stable. This is mainly because the surface samples are vulnerable to factors such as wind, sunlight, and precipitation in the natural environment. Pyrite is prone to oxidation, and the alkaline substances in the tailings migrate with rainwater and other behaviors, resulting in a decrease in pH. However, the pH value of each sampling point of the surface tailings still remains between 7.5 and 9.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.3 The distribution and occurrence forms of cyanide in tailings\u003c/h2\u003e\u003cp\u003eAfter cyanide enters the tailings pond for storage along with the tailings, under the influence of wind, sunlight, precipitation, microorganisms, and human activities in the natural environment, a series of migration and transformation behaviors such as volatilization, oxidation, hydrolysis, complexation, complex precipitation, and biological transformation occur, resulting in changes in the spatial distribution of the cyanide content in the tailings pond. The spatial distribution of the cyanide content (Fig. S4) shows that the overall cyanide content is lower at the top and higher at the bottom, and lower near the source and higher further away. According to the sampling points, the cyanide content in the tailings at sampling points 1#-5# is generally lower than that at sampling points 6#-9#. Among them, the cyanide content in the tailings at sampling point 1# is the lowest, and the cyanide content in the tailings at sampling point 9# is the highest. This is related to the location characteristics of the sampling points and the water content (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The terrain at sampling point 1# is the highest, and the terrain at sampling point 9# is the lowest. The change trend of the cyanide content is basically consistent with that of the water content because the CN bond in cyanide is a covalent bond with strong polarity, which is extremely soluble in water and prone to migration with the water flow.\u003c/p\u003e\u003cp\u003eFrom the variation trend of the cyanide content in the tailings and their toxic leachates at different sampling points (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), it can be seen that the cyanide content generally shows a trend of gradually increasing with the increase of the sampling depth. This is because the surface tailings are prone to air drying, precipitation scouring, oxidation and other effects, resulting in a relatively large decrease in the cyanide content in the tailings. The cyanide content in the middle and deep tailings at sampling points 7#-9# is relatively high. This is because the terrain at sampling points 7#-9# is relatively low, the water content in the tailings is relatively high, the middle and deep tailings are well sealed, and the amount of natural degradation of cyanide is relatively small. In addition, the variation trend of the cyanide content in the toxic leachates of the tailings with the sampling depth is basically consistent with the change of the cyanide content in the tailings, indicating that the cyanide in the tailings can be dissolved during water immersion and migrate with precipitation.\u003c/p\u003e\u003cp\u003eIn addition, the variation trend of the proportion of CN\u003csub\u003ef\u003c/sub\u003e to CN\u003csub\u003et\u003c/sub\u003e in the tailings at different sampling points (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) shows that the overall CN\u003csub\u003ef\u003c/sub\u003e/CN\u003csub\u003et\u003c/sub\u003e increases with the increase of the sampling depth. The CN\u003csub\u003ef\u003c/sub\u003e/CN\u003csub\u003et\u003c/sub\u003e in the tailings at sampling points 7#-9# is higher than that at other sampling points. The main reason is that the natural degradation of cyanide in the surface tailings is relatively severe, and the degradation mainly occurs in the form of CN\u003csub\u003ef\u003c/sub\u003e, resulting in a lower CN\u003csub\u003ef\u003c/sub\u003e/CN\u003csub\u003et\u003c/sub\u003e. At sampling points 7#-9#, due to the relatively slow natural degradation, the decrease in the CN\u003csub\u003ef\u003c/sub\u003e content is relatively small, and the CN\u003csub\u003ef\u003c/sub\u003e/CN\u003csub\u003et\u003c/sub\u003e remains relatively high.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.4 The distribution and occurrence forms of heavy metals in tailings\u003c/h2\u003e\u003cp\u003eThe tailings from sampling points 2#, 5#, and 8# in the middle of the tailings pond were selected as the experimental objects. Heavy metals with high contents in the tailings, including Cu, Zn, Pb, Cd, Ni, and Mn, were chosen as pollution factors to analyze the changes in heavy metal speciation at different sampling depths.\u003c/p\u003e\u003cp\u003eThe speciation distribution of Cu in tailings at different depths of each sampling point (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) shows that the residual Cu accounts for approximately 45\u0026ndash;60% in the middle-deep layer samples, while it accounts for 81\u0026ndash;83% in the surface samples. The exchangeable Cu accounts for 16\u0026ndash;33% in the middle-deep layer samples and 3\u0026ndash;10% in the surface samples. The proportions of reducible Cu and oxidizable Cu are both reduced to varying degrees in the surface tailings, indicating that a large amount of Cu in the surface tailings is released and migrated, and another part undergoes redox reactions and is eroded, thereby being released. Since Cu mainly exists in chalcopyrite, it is relatively easy to be oxidized and decomposed in the natural environment.\u003c/p\u003e\u003cp\u003eThe horizontal distribution of Cu speciation from sampling point 2# to 8# shows that the proportion of exchangeable Cu generally increases gradually, while the proportion of residual Cu decreases gradually, suggesting that the released exchangeable Cu migrates to low-lying areas with water flow.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe distribution of the four speciations of Zn in tailings at different depths of each sampling point (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) is relatively dispersed. The surface layer is dominated by residual Zn, while the middle-deep layer is mostly composed of exchangeable Zn. The proportions of reducible and oxidizable Zn show very small variation ranges with the increase of sampling depth. This is because Zn in the tailings mainly exists in sphalerite, which is relatively stable in the natural environment and hardly undergoes redox reactions. Exchangeable species generally refer to water-soluble, exchangeable heavy metals combined with carbonates, which are mainly adsorbed on the surface of tailings or exist in the form of hydroxides and carbonates. The lower content of exchangeable Zn in surface tailings is due to the vertical and horizontal migration of exchangeable Zn with precipitation to deeper layers and low-lying areas, which is reflected by the increase in the proportion of exchangeable Zn in middle-deep tailings samples and tailings samples from sampling points 5# and 8#.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe morphological distribution of Pb in tailings at different depths of each sampling point (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) is dominated by the residual form, accounting for approximately 55%-66%. The exchangeable form comes second, accounting for about 22%-30%. The proportions of the reducible form (5%-10%) and the oxidizable form (5%-14%) are the smallest.\u003c/p\u003e\u003cp\u003eAnalysis of the morphology of Pb in tailings samples at different depths shows that the proportion of the residual form of Pb is the largest at a depth of 0.5 m, with relatively less distribution of the other three forms, and the oxidizable form has the least distribution. This is because the surface-layer tailings are most affected by the natural environment, being prone to oxidation, erosion, and hydrolysis, resulting in the transformation of oxidizable Pb into the exchangeable and residual forms. The morphology of Pb in tailings at depths from 2.5 m to 8.5 m shows an irregular distribution.\u003c/p\u003e\u003cp\u003eA comparative analysis of the morphology of Pb in tailings samples at the same depth in each sampling point reveals that from sampling point 2# to 8#, the proportion of exchangeable Pb in tailings samples at depths of 0.5 m and 2.5 m gradually increases. This is because the terrain from sampling point 2# to 8# gradually descends, and exchangeable Pb migrates downward with water flow, leading to an increase in the content of exchangeable Pb in tailings at lower-lying areas. Tailings at depths from 4.5 m to 8.5 m are less disturbed by the outside world, and the morphology of Pb basically maintains its original distribution with small-scale irregular fluctuations.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the morphological distribution of Cd in tailings at different depths of each sampling point (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), the residual form dominates overall, with a proportion ranging from 58\u0026ndash;79%. It is particularly high in surface layer tailings samples, accounting for 77%-79%. The distributions of the other three forms are relatively dispersed, with the lowest proportions in the surface layer.\u003c/p\u003e\u003cp\u003eAnalysis of the morphological distribution of Cd in tailings at the same depth but different sampling points shows that from sampling point 2# to 8#, as the terrain descends, except that the proportion of exchangeable Cd in tailings samples generally increases slightly, the other three forms basically fluctuate slightly and irregularly. This indicates that, apart from the vertical and horizontal migration of exchangeable Cd adsorbed on the surface of tailings, the other forms of Cd remain relatively stable. This is because Cd mainly exists in silicate minerals, which is relatively stable.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the morphological distribution of Ni in tailings at different depths of each sampling point (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), the residual form dominates overall, with a proportion ranging from 54\u0026ndash;76%. The exchangeable form comes second, accounting for 13%-25%, while the reducible and oxidizable forms have the smallest proportions, ranging from 4%-14% and 4%-17% respectively.\u003c/p\u003e\u003cp\u003eThe proportion of the residual form of Ni in surface layer tailings is 12%-20% higher than that in middle and deep layer tailings, while the proportions of the other three forms are lower. This is mainly because, affected by natural conditions such as oxidation, weathering, and precipitation induced erosion, the exchangeable Ni in surface layer tailings has migrated. This also indicates that Ni is mainly adsorbed on the surface of tailings or exists in minerals such as pyrite that are prone to erosion and decomposition.\u003c/p\u003e\u003cp\u003eA comparative analysis of the morphology of Ni in tailings samples at the same depth across different sampling points shows that from sampling point 2# to 8#, the proportion of exchangeable Ni in tailings samples generally shows an increasing trend. This indicates that as the terrain of the sampling points lowers, exchangeable Ni migrates downward with water flow, resulting in an increase in the content of exchangeable Ni in tailings at lower lying areas.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the morphological distribution of Mn in tailings at different depths of each sampling point (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e), the residual form also predominates, accounting for 40\u0026ndash;60%, with the other three forms distributing relatively evenly. The proportion of residual Mn is higher in surface tailings samples, while the proportion of oxidizable Mn is lower, indicating that Mn-associated minerals in the surface tailings, such as pyrite and chalcopyrite, are oxidatively decomposed. Part of Mn is converted into the exchangeable form and migrates with water flow, leading to an increase in the proportion of exchangeable Mn in surface tailings at low-lying areas (evident by the significant increase in exchangeable Mn proportion in tailings at 2.5 m depth), while another part exists as residual form in silicate minerals. Additionally, the morphology of Mn remains relatively stable at depths of 4.5\u0026ndash;8.5 m across all sampling points, suggesting limited vertical migration of Mn in the middle-deep layers.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.5 Environmental risk and management insights from cyanidation tailings studies\u003c/h2\u003e\u003cp\u003eThese findings provide guidance for the environmental risk assessment and management of cyanide tailings. For risk evaluation, prioritize monitoring free cyanide in liquids 57.65% of total cyanide, with 73.46% in liquid phase over total cyanide alone, as CN\u003csub\u003ef\u003c/sub\u003e directly indicates leaching/toxicity risks. Spatial heterogeneity, with higher CN\u003csub\u003et\u003c/sub\u003e, CN\u003csub\u003ef\u003c/sub\u003e/CN\u003csub\u003et\u003c/sub\u003e ratios, and moisture in deeper, lower zones, demands stratified/zoned sampling to identify hotspots. For heavy metals, though residual fractions dominate, increased exchangeable forms in 2.5\u0026ndash;8.5 m layers and vertical variations in reducible/oxidizable fractions signal potential activation, requiring long-term bioavailability checks.\u003c/p\u003e\u003cp\u003eManagement should target liquid cyanide via in-situ fixation and moisture control (e.g., liners). Stratified approaches are key: stabilize/extract deep high moisture zones; cap surfaces to prevent infiltration. Tailor heavy metal remediation use adsorbents for exchangeable fractions, control redox for reducible/oxidizable forms. Shift to precision governance with dynamic monitoring of cyanide speciation, metal fractions, and moisture to minimize risks.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis study systematically elucidated the occurrence mechanisms of cyanide and heavy metals in cyanidation tailings. By comprehensively analyzing the content and speciation of CN\u003csub\u003et\u003c/sub\u003e, CN\u003csub\u003ef\u003c/sub\u003e and CN\u003csub\u003ed\u003c/sub\u003e across multiphase media (pulp, filtrate, and tailings solids), it was determined that 73.46% of the cyanide resides in the liquid phase of the tailings, with CN\u003csub\u003ef\u003c/sub\u003e accounting for 57.65% of the total. These findings underscore the predominant liquid-phase distribution of cyanide and its associated elevated environmental risk.\u003c/p\u003e\u003cp\u003eSpatial sampling across the tailings impoundment revealed a significant increase in CN\u003csub\u003et\u003c/sub\u003e content and the CN\u003csub\u003ef\u003c/sub\u003e/CN\u003csub\u003et\u003c/sub\u003e ratio with increasing depth and decreasing elevation, demonstrating a strong positive correlation with water content. Heavy metals, including Cu, Zn, Pb, Cd, Ni, and Mn, are predominantly hosted within sulfide minerals such as pyrite, sphalerite, chalcopyrite, and galena. While these metals are mainly present in residual forms overall, the proportion of exchangeable fractions notably increases in the middle deep strata (2.5\u0026ndash;8.5 m). Moreover, the reducible and oxidizable fractions of Cu, Pb, Ni, and Mn exhibit distinct vertical differentiation patterns, indicating complex geochemical processes within the tailings matrix.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by the National Natural Science Foundation of China (42277004) and the National Key Research and Development Program of China (2022YFC3702104).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of interest statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by the National Natural Science Foundation of China (42277004) and the National Key Research and Development Program of China (2022YFC3702104).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eQiang Liu: Conceptualization, methodology, investigation, formal analysis, manuscript writing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eJiyan Shi: Conceptualization, funding acquisition, review \u0026amp; editing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll participants agree to participate in the study, understand the purpose, risks, and benefits of the study, and also agree to abide by all the regulations and conditions of the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis manuscript has not been published or presented elsewhere in part or in entirety, and is not under consideration by another journal. All the authors have approved the manuscript and agree with submission to your esteemed journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data used in this research are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study did not involve human or animal subjects, so ethical approval was not applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen, Y., Song, Y.H., Chen, Y., Zhang, X.W., Lan, X.Z., 2020. Comparative experimental study on the harmless treatment of cyanide tailings through slurry electrolysis. Sep. Purif. Technol. 251, 117314.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDobrosz-G\u0026oacute;mez, I., Garc\u0026iacute;a, B.D.R., GilPavas, E., Garc\u0026iacute;a, M.\u0026Aacute;.G., 2017. Kinetic study on HCN volatilization in gold leaching tailing ponds. Miner. Eng. 110, 185\u0026ndash;194.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDonato, D.B., Nichols, O., Possingham, H., Moore, M., Ricci, P.F., Noller, B.N., 2007. A critical review of the effects of gold cyanide-bearing tailings solutions on wildlife. Environ. Int. 33, 974\u0026ndash;984.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDong P., Song Y.H., Wu L., Bao J., Yin N., Zhu R.Y., Li Y.F., Li H.F., 2024. Efficient recovery of iron from anaerobic roasted cyanide tailings using advanced oxidation technology. Hydrometallurgy. 224, 106241.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFaraz, S., Hossna, D., Rezgar, B., Piroz, Z., 2014. Improved recovery of a low-grade refractory gold ore using flotation\u0026ndash;preoxidation\u0026ndash;cyanidation methods. Int. J. Min. Sci. Tec. 24, 537\u0026ndash;542.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFrimmel, H.E., 2018. Episodic concentration of gold to ore grade through Earth's history. Earth-sci. Rev. 180, 148\u0026ndash;158.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFu P.F., Li Z.Y., Feng J., Bian Z.Z., 2018. Recovery of Gold and Iron from Cyanide Tailings with a Combined Direct Reduction Roasting and Leaching Process. Metals. 8, 561.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHamberg, R., Maurice, C. and Alakangas, L., 2015. Use of cemented paste backfill based on arsenic\u0026ndash;rich tailings from cyanidation. In International Conference on Acid Rock Drainage and IMWA Annual conference.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHasab, M.G., Rashchi, F., Raygan, S., 2014. Chloride\u0026ndash;hypochlorite leaching and hydrochloric acid washing in multi-stages for extraction of gold from a refractory concentrate. Hydrometallurgy. 142, 56\u0026ndash;59.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJaszczak, E., Polkowska, Z., Narkowicz, S., Namiesnik, J., 2017. Cyanides in the environment-analysis-problems and challenges. Environ. Sci. Pollut. Control Ser. 24, 15929\u0026ndash;15948.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKiventer\u0026auml;, J., Lancellotti, I., Catauro, M., Poggetto, F.D., Leonelli, C., Illikainen, M., 2018. Alkali activation as new option for gold mine tailings inertization. J. Clean. Prod. 187, 76\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKorte, F., Spiteller, M., Coulston, F., 2000. The cyanide leaching gold recovery process is a non-sustainable technology with unacceptable impacts on ecosystems and humans: The disaster in Romania. Ecotox. Environ. Safe. 46, 241\u0026ndash;245.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKuyucak, N., Akcil, A., 2013. Cyanide and removal options from effluents in gold mining and metallurgical processes. Miner. Eng. 50\u0026ndash;51, 13\u0026ndash;29.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKyle, J.H., Breuer, P.L., Bunney, K.G., Pleysier, R., 2012. Review of trace toxic elements (Pb, Cd, Hg, As, Sb, Bi, Se, Te) and their deportment in gold processing: Part II: deportment in gold ore processing by cyanidation. Hydrometallurgy. 111, 10\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi H.Y., Long H.L., Zhang L.B., Yin S.H., Li S.W., Zhu F., Xie H.M., 2020. Effectiveness of microwave-assisted thermal treatment in the extraction of gold in cyanide tailings. J. Hazard. Mater. 384, 121456.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMekuto, L., Ntwampe, S.K.O., Akcil, A., 2016. An integrated biological approach for treatment of cyanida-tion wastewater. Sci. Total. Environ. 571, 711\u0026ndash;720.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNiu, M.X., Ge, X.X., Dai, Y.G., Jin, X., Sun, W.W., Hu, X.L., 2024. Effects of sintering parameters on the preparation and properties of foamed ceramics from cyanide tailings. J. Asian. Ceram. Soc. 1\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOudjehani, K., Zagury, G. and Desch\u0026ecirc;nes, L., 2002. Natural attenuation potential of cyanide via microbial activity in mine tailings. Appl. Microbiol. Biotechnol. 58, 409\u0026ndash;415.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRoche, C., Thygesen, K., Baker, E., 2017. Mine tailings storage: safety is no accident. a UNEP rapid response assessment. United Nations Environment Programme. New York, US: Springer.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShu, X.H., Zhang, Q., Lu, G.N., Yi, X.Y., Dang, Z., 2018. Pollution characteristics and assessment of sulfide tailings from the Dabaoshan Mine, China. Int. Biodeter. Biodegr. 128, 122\u0026ndash;128.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTeimouri, S., Potgieter, J.H., Simate, G.S., Van Dyk, L., Dworzanowski, M., 2020. Oxidative leaching of refractory sulphidic gold tailings with an ionic liquid. Miner. Eng. 156, 106484.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTran, Q.B., Lohitnavy, M., Phenrat, T., 2019. Assessing potential hydrogen cyanide exposure from cyanide-contaminated mine tailing management practices in Thailand\u0026rsquo;s gold mining. J. Environ. Manag. 249, 109357.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang, J., Wang, W., Dong, K., Fu, Y., Xie, F., 2019. Research on leaching of carbonaceous gold ore with copper-ammonia-thiosulfate solutions. Miner. Eng. 137, 232\u0026ndash;240.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang, Z.Q., Hong, C., Xing, Y., Wang, K., Li, Y.F., Feng, L.H., Ma, S.L., 2018. Spatial distribution and sources of heavy metals in natural pasture soil around copper-molybdenum mine in Northeast China. Ecotox. Environ. Safe. 154, 329\u0026ndash;336.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWikedzi, A., Arinanda, M.A., Lei\u0026szlig;ner, T., Peuker, U.A., M\u0026uuml;tze, T., 2018. Breakage and liberation characteris-tics of low grade sulphide gold ore blends. Miner. Eng. 115, 33\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXu, Y., Li, W.Y., Liu, Y.Q., Liu, J.C., Li, L., Yan, D.H., 2022. Long-term degradation characteristics of cyanide in closed monofills and its effects on the environment and human health: Evidence from nine landfill sites in northen China. Sci. Total. Environ. 839, 156269.\u003c/span\u003e\u003c/li\u003e\u003c/ol\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":"Cyanide tailings, Cyanide, Heavy metals, Occurrence patterns","lastPublishedDoi":"10.21203/rs.3.rs-7387467/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7387467/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCyanide leaching, the mainstream gold extraction process, generates substantial cyanide tailings annually, posing a persistent environmental challenge due to their hazardous nature. Uncertainties surrounding cyanide speciation and migration mechanisms have impeded advancements in safe disposal and resource recovery strategies.\u003c/p\u003e\u003cp\u003eThis study investigated the physicochemical properties and occurrence patterns of cyanide/heavy metals in typical cyanidation tailings. Key findings include:\u003c/p\u003e\u003cp\u003e(1) Multi-phase speciation analysis revealed 73.46% of total cyanide (CN\u003csub\u003et\u003c/sub\u003e) resided in the liquid phase, with free cyanide (CN\u003csub\u003ef\u003c/sub\u003e) accounting for 57.65% of CN\u003csub\u003et\u003c/sub\u003e, indicating high leaching potential and environmental risk.\u003c/p\u003e\u003cp\u003e(2) Spatial profiling within the tailings pond showed CN\u003csub\u003et\u003c/sub\u003e concentrations and CN\u003csub\u003ef\u003c/sub\u003e/CN\u003csub\u003et\u003c/sub\u003e ratios increased with depth and decreasing elevation, strongly correlating with moisture content.\u003c/p\u003e\u003cp\u003e(3) Heavy metals (Cu, Zn, Pb, Cd, Ni, Mn) were primarily associated with sulfide minerals (pyrite, sphalerite, etc.), existing mainly in residual forms. However, exchangeable fractions significantly increased in mid-deep layers (2.5\u0026ndash;8.5 m), while reducible/oxidizable fractions exhibited distinct vertical variations.\u003c/p\u003e\u003cp\u003eThese results provide critical insights for optimizing tailings management and developing targeted remediation strategies.\u003c/p\u003e","manuscriptTitle":"Speciation and Spatial Distribution of Cyanide and Heavy Metals in Cyanidation Tailings: Implications for Environmental Risk and Management","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-10 15:49:51","doi":"10.21203/rs.3.rs-7387467/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":"6c9e7890-f873-4362-bc9b-f1d904f64fb0","owner":[],"postedDate":"September 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-01T13:38:55+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-10 15:49:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7387467","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7387467","identity":"rs-7387467","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}