Determination of heavy metals in surface and ground water systems and its public health implication in Osogbo town, Osun State

Determination of heavy metals in surface and ground water systems and its public health implication in Osogbo town, Osun State | 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 Article Determination of heavy metals in surface and ground water systems and its public health implication in Osogbo town, Osun State Sefiyah Oluwakemi Adeyemo, Kamilu Ayo Fasasi, Abdur-rahman Kolawole Mustapha, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6127785/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 Portable sources of surface and groundwater are constantly polluted by anthropogenic activities and have negative impacts on human and animals’ health. This study investigated seasonal variation of heavy metals in Osun River and selected wells in Osogbo town, Osun State, Nigeria, to ascertain their public health impacts. Water samples from surface and groundwater systems were examined using PG990 atomic absorption spectrophotometer to determine heavy metal concentrations of surface and groundwater systems in Osogbo town, Osun State, Nigeria. The concentrations of 13 heavy metals (Arsenic, Copper, Cobalt, Lead, Nickel, Iron, Zinc, Chromium, Manganese, Sodium, Magnesium, Calcium and Potassium) in well (groundwater) and surface water (Osun River) were within international limits except for Cadmium and Mercury which were observed to be above 0.005mg/l limits in dry and wet seasons. This study showed that the surface and groundwater systems assessed were contaminated with heavy metals in dry and wet seasons which portend health risks to consumers in the study area. Also, there is a need for appropriate treatment and regulation of the activities of miners and residents that contribute to the contamination and pollution of these sources of portable water to forestall public health disasters in the study area. Biological sciences/Ecology Biological sciences/Zoology Groundwater surface water heavy metals dry season wet season Osogbo Figures Figure 1 Figure 2 Figure 3 Introduction Groundwater recharge occurs when water from precipitation or surface water bodies infiltrates into the ground replenishing the aquifers [ 1 ]. Groundwater contributes to base flow in rivers, ensuring a sustained flow during dry periods when surface water alone may not be sufficient to maintain stream flow [ 2 ]. The interaction of ground and surface water involves many physical, chemical and biological processes that take place in a variety of physiographic and climatic settings [ 3 ]. Surface and groundwater are important to man, animals and environment for domestic, household, industrial, transportation, fishing, tourism and cultural purposes [ 4 ]. Heavy metals contamination of surface and groundwater, reduce the quality of drinking and irrigation water, as well as the food web structure thereby, posing great risk to humans, animals and the environment [ 5 ]. Heavy metals are not only regarded as natural trace components of the environment but are also commonly known as environmental pollutants particularly when prevalent due to anthropogenic activities [ 6 ]. Their occurrences not only originate from natural factors such as the weathering of soils and rocks, but also from anthropogenic inputs such as industrial wastes, agricultural and mining activities [ 7 ]. Metal concentrations in freshwater sources (rivers, lakes, etc.) can be regarded as a good indicator of the freshwater contamination [ 8 ]. This work is aimed at determining the heavy metals status in surface and groundwater systems and its public health implication in the study area. Materials and Methods 2.1 Study area Osun River is located in southwestern Nigeria and is one of the key characteristics and features of Osun State (7.5629ºN, 4.5200ºE). The Osun River is situated in the southwestern part of Nigeria, primarily flowing through Osun and Oyo states. Osun River originates from Igede-Ekiti (in Ekiti State) and flows southwards through Southwestern Nigeria into the Lagos lagoon and the Atlantic Gulf of Guinea. Before flowing across Osogbo town in Osun State, the river meanders through many rainforests, farmlands and villages. The river flows across the southern part of Osogbo city (Fig. 1 ) and serves as habitat to various fauna, especially catfish which are trapped and sold by local fishermen. The study areas covered the pre-urban and urban parts of the river. The sampling locations in this study have peculiar characteristics. Osun-jela is situated beside a bridge dividing Owode town with population of 83,831 (2006 census) from Osun-jela community (a rural settlement). It is about 25m from Osogbo-Ilesa road. Oke-ijetu (urban settlement) is beside a bridge along the newly constructed Oke-ijetu road with relatively less urban activities which is about 1km from Fountain University. This portion of the river accommodates some rocks, which form its base. Aregbe (urban settlement) is densely populated with anthropogenic activities, domestic and industrial wastes [ 9 ]. 2.2 Sample Collection Water samples were collected from surface water (Osun River) and groundwater (well) at Osunjela (7.739645°N 4.597762°E, 7.738606°N 4.596087°E and 7.737615°N 4.595897°E), Oke-ijetu (7.742508°N 4.556423°E, 7.743365°N 4.555888°E and 7.744362°N 4.555222°E) and Aregbe (7.767707°N 4.539669°E, 7.768203°N 4.539238°E and 7.768703°N 4.539010°E). Twelve water samples were collected from surface water (Osun River) and three water from groundwater (well) at Osunjela, Oke-ijetu and Aregbe each from upstream, midstream and downstream respectively from Osogbo town (Osogbo and Olorunda LGAs), Osun State, Nigeria in dry and wet seasons. The sampling was done for four months (March- June, 2024) because it was done at the peak of dry and wet seasons which corresponded with the peak of anthropogenic activities in the study areas. The samples were collected from upstream, downstream and midstream at a specific point respectively across the study area from the two sources [well (groundwater) and Osun River (surface water)] respectively monthly. Samples were transported to atomic absorption spectrophotometer laboratory (AAS), Centre for Energy Research and Development (CERD), Obafemi Awolowo University, Ile-Ife, Nigeria for further analysis [ 10 , 11 and 12 ]. 2.3 Digestion of water samples 25ml each of the filtered samples were measured into clean conical flasks. 15ml of freshly prepared aqua-regia was added into each flask and were each heated to near dryness. 10ml of distilled water was then added and heated again for 2–3 minutes, allowed to cool and filtered. The filtrates were each made up to mark in a 25ml flask and kept refrigerated pending metal determination by AAS [ 10 , 11 and 13 ]. 2.4 CALIBRATION Before analyzing digested water, sediment and fish samples for metal concentration, PG990 AAS was calibrated with the use of standard reference material. Each of the metals has its own different standard concentrations which were prepared from the stock solution (1000ppm) for each cation. 2.5 Determination of cations (Heavy Metals) in water The digested water samples was analyzed with PG990 atomic absorption spectrophotometer of the Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria for the heavy metals in the samples by flame atomization, using air-acetylene flame and single element hollow cathode lamp which generated absorbance values and concentrations for each of the heavy metals were generated automatically by software called AA win. This absorption follows Beer-Lambert’s law which states the absorbance to be directly proportional to the path length in the flame and to the concentration of atomic vapor in the flame [ 10 , 11 and 12 ]. 2.6 Data Analysis Data analysis for the heavy metals involved processing and interpretation of the data generated from the Flame Atomic Absorption Spectroscopy (FAAS), using descriptive statistics. Results Fifteen cations (Arsenic, Copper, Lead, Nickel, Iron, Zinc, Chromium, Manganese, Magnesium, Sodium, Calcium, Cadmium, Cobalt, Mercury and Potassium) were detected in the water samples from Osun River and selected wells from the study area. Thirteen cations with different concentrations were detected in both seasons {Arsenic (0.005 ± 0.003 to 0.018 ± 0.008mg/l), Copper (0.028 ± 0.023 to 0.058 ± 0.011mg/l), Cobalt (0.013 ± 0.001 to 0.028 ± 0.017mg/l), Lead (0.004 ± 0.004 to 0.016 ± 0.013mg/l), Nickel (0.014 ± 0.008 to 0.039 ± 0.008mg/l), Iron (0.021 ± 0.013 to 0.057 ± 0.005mg/l), Zinc (0.017 ± 0.004 to 0.047 ± 0.019mg/l), Chromium (0.011 ± 0.001 to 0.039 ± 0.001mg/l), Manganese (0.012 ± 0.012 to 0.025 ± 0.021mg/l), Magnesium (0.028 ± 0.004 to 0.070 ± 0.014mg/l), Sodium (0.018 ± 0.004 to 0.046 ± 0.006mg/l), Calcium (0.024 ± 0.003 to 0.044 ± 0.011mg/l) and Potassium (0.026 ± 0.014 to 0.060 ± 0.028mg/l) (dry season)} and Arsenic (0.004 ± 0.001 to 0.105 ± 0.002mg/l), Copper (0.036 ± 0.004 to 0.077 ± 0.011mg/l), Cobalt (0.003 ± 0.001 to 0.020 ± 0.013mg/l), Lead (0.004 ± 0.001 to 0.011 ± 0.003mg/l), Nickel (0.009 ± 0.001 to 0.037 ± 0.026mg/l), Iron (0.016 ± 0.006 to 0.067 ± 0.014mg/l), Zinc (0.021 ± 0.006 to 0.067 ± 0.004mg/l), Chromium (0.013 ± 0.002 to 0.043 ± 0.023mg/l), Manganese (0.016 ± 0.014 to 0.037 ± 0.040mg/l), Magnesium (0.034 ± 0.005 to 0.078 ± 0.018mg/l), Sodium (0.058 ± 0.042 to 0.096 ± 0.064mg/l), Calcium (0.023 ± 0.004 to 0.096 ± 0.064mg/l) and Potassium (0.035 ± 0.024 to 0.106 ± 0.023mg/l (wet season)} which were within WHO (2018) and EU (2020) limits. While Cadmium [(0.014 ± 0.008 to 0.035 ± 0.002mg/l) (Dry season)}; (0.012 ± 0.002 to 0.026 ± 0.003mg/l) (Wet season)] and Mercury [(0.005 ± 0.002 to 0.012 ± 0.012mg/l) (Dry season); (0.002 ± 0.000 to 0.080 ± 0.003mg/l) (wet season)] in Osun River and Wells exceeded 0.005mg/l according to WHO (2018) and EU (2020) limits (Figs. 2 and 3). a b a b Figure 3: Concentrations of cations (heavy metals) analyzed from the surface water (Osun River) and groundwater (wells) in wet season Discussion The study revealed that the Osun River and Groundwater systems in Osogbo Town of Osun State, Nigeria were contaminated with fifteen cations (Arsenic, Copper, Lead, Nickel, Iron, Zinc, Chromium, Manganese, Magnesium, Sodium, Calcium, Cadmium, Cobalt, Mercury and Potassium) in Osun River and wells using Atomic Absorption Spectroscopy (AAS) where two cations (Cadmium and Mercury) were above 0.005mg/l according to the international limits {WHO (2018) and EU (2020)} limits in dry and wet seasons [14 and 15]. Adeyemi and Zacchaeus, (2021) determined the mean concentrations of eight cations (Nickel, Lead, Chromium, Manganese, Copper, Cadmium, Zinc and Iron) in groundwater (hand-dug wells and boreholes) collected from Ota and Sagamu industrial areas, Ogun State, Nigeria using Atomic Absorption Spectroscopy (AAS) where Lead and Iron exceeded the safe limits of WHO (2017) during dry and wet seasons [ 16 ]. Mustapha et al . (2021) determined the mean concentrations of six cations (Zinc, Copper, Manganese, Iron, Lead and Cadmium) in Epe Lagoon, Lagos, Nigeria where Lead and Cadmium exceeded WHO (2003) safety limits [ 17 ]. Conclusion The concentration of heavy metals in surface and groundwater systems in Osogbo metropolis were within safe limits according to international standards in dry and wet seasons, although there were slight seasonal variations across upstream, midstream and downstream. While, Mercury (Hg) and Cadmium (Cd) were observed to be high in concentrations above safety limits in both surface and groundwater systems in dry and wet seasons according to WHO and EU’s safety limits. This study showed that surface and groundwater systems assessed were contaminated with heavy metals in dry and wet seasons which portend health risks to consumers in the study area. Recommendation There is a need for appropriate treatment of surface and groundwater systems before consumption by residents in the study area. Also, there is a need to regulate the activities of miners and residents that contribute to the contamination and pollution of these sources of portable water to forestall public health disasters in the study area. Declarations CONFLICT OF INTEREST There is no conflict of interest amongst the authors for this paper to be published. DATA DECLARATION STATEMENT The datasets generated and/or analyzed during the study are available in a supplementary file. Author Contribution S. O. wrote the main manuscript text while the other authors reviewed the manuscript Acknowledgement I am deeply grateful to Professor Sidney Obidimma Nzeako from Department of Animal and Environmental Biology, University of Port Harcourt for his invaluable encouragement, motivation, inspiration, support, guidance and mentorship throughout this research. Data Availability Data is provided as a supplementary information file References Harvey, J. W. & Bohlke, J. K. Contributions of stream water and groundwater to the chemistry of a praire stream, Konza Creek, Kansas, USA. J. Hydrol. 278 (1–4), 210–225 (2003). Winter, T. C. The role of groundwater in generating stream flow in headwater areas and in maintaining base flow. J. Am. Water Resour. Assoc. 43 (1), 15–25 (2007). Sophocleous, M. A. Interactions between groundwater and surface water: The state of the science. Hydrogeol. J. 10 , 52–67 (2002). Oyekunle, O., Adekunle, J., Ogunfowokan, A. O., Olutona, G. O. & Durosinmi, M. Hydrology for disaster management total and exchangeable metals in groundwater of Ile-Ife, Southwestern Nigeria. Special Publication of the Nigerian Association of Hydrological Sciences, 208–223. (2012). https:publications.funaab.edu.ng/index.php/NAHS/article/download/929/897 Adesiyan, I. M. et al. Concentrations and human health risk of heavy metals in rivers in Southwest Nigeria. J. Health pollution . 8 (19), 180–907 (2018). Paul, B. T., Clement, G. Y., Anita, K. P. & Dwayne, J. S. Heavy metals toxicity and the environment. Natl. Cent. Biotechnol. Inform. 101 , 133–164 (2012). Wan, Y. L., Ahmad, Z. A. & Mohammad, P. Z. Spatial variability of metals in surface water and sediment in the Langat River and geochemical factors that influence their water-sediment interactions, Malaysia. Sci. World J. 10 , 150–652 (2012). Saravanan, P. et al. Comprehensive review on toxic heavy metals in the aquatic system: Sources, identification, treatment strategies and health risk assessment. Environ. Res. 258 , 119–440 (2024). Anifowose, A. & Oyebode, A. W. Studies on heavy metals contents of Osun River at the pre-urban settlement and across Osogbo City, Nigeria. J. Taibah Univ. Sci. 13 (1), 318–323 (2019). APHA. : Standard methods for the examination of water and wastewater (21st edition), American Public Health Association/American Water Works Association/ Water Environment Federation, Washington DC, 318-340pp (2005). Olabanji, I. O. & Oluyemi, E. A. Heavy Metals Determination in Some Species of Frozen Fish Sold at the Ile-Ife Main Market, Ife, South-West Nigeria. J. Sci. 13 , 86–93 (2011). Makinde, O. W. et al. Heavy metal contamination in stream water and sediments of gold mining areas of Southwestern, Nigeria. Afr. J. Environ. Sci. Technol. 10 (5), 150–161 (2016). Bankaji, I. et al. Comparison of Digestion Methods using Atomic Absorption Spectrometry for the Determination of Metals Levels in plants. Separations 10 , 40 (2023). World Health Organization (WHO). A global overview of national regulations and standard for drinking-water quality (2018). https://www.who.int/publications/i/item/9789241513760 European Union Directive (EU). 2020/2184 on the quality of water intended for human consumption https://www.fao.org/faolex/results/details/en/c/LEX-FAOC201243/ Adeyemi, A. A. & Zacchaeus, O. O. Concentrations and health risk assessment of industrial heavy metals pollution in groundwater in Ogun state, Nigeria. Sci. Afr. 11 (1), 666 (2021). Mustapha, A. M., Ugya, A. Y. & Mustapha, Z. Assessment of heavy metals levels in fish tissues, water and sediment from Epe Lagoon, Lagos, Nigeria. Sci. World J. , 16 (4). (2021). Additional Declarations No competing interests reported. Supplementary Files supplementaryfile.xls 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-6127785","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":441477683,"identity":"b90428dc-690a-4ed2-9508-f632e351f180","order_by":0,"name":"Sefiyah Oluwakemi 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3","display":"","copyAsset":false,"role":"figure","size":66546,"visible":true,"origin":"","legend":"\u003cp\u003eConcentrations of cations (heavy metals) analyzed from the surface water (Osun River) and groundwater (wells) in wet season\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6127785/v1/fa0ca21f19efda98f314528c.png"},{"id":81365711,"identity":"afd7343f-8205-4608-8b5e-eb22b74c20c0","added_by":"auto","created_at":"2025-04-25 09:23:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":972327,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6127785/v1/be579a2f-f1ae-40b1-a93d-db2c3fbb8150.pdf"},{"id":80724164,"identity":"7bab11c9-65e3-486d-912c-9b5e1bdc7e6d","added_by":"auto","created_at":"2025-04-16 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Groundwater contributes to base flow in rivers, ensuring a sustained flow during dry periods when surface water alone may not be sufficient to maintain stream flow [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The interaction of ground and surface water involves many physical, chemical and biological processes that take place in a variety of physiographic and climatic settings [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Surface and groundwater are important to man, animals and environment for domestic, household, industrial, transportation, fishing, tourism and cultural purposes [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Heavy metals contamination of surface and groundwater, reduce the quality of drinking and irrigation water, as well as the food web structure thereby, posing great risk to humans, animals and the environment [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Heavy metals are not only regarded as natural trace components of the environment but are also commonly known as environmental pollutants particularly when prevalent due to anthropogenic activities [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Their occurrences not only originate from natural factors such as the weathering of soils and rocks, but also from anthropogenic inputs such as industrial wastes, agricultural and mining activities [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Metal concentrations in freshwater sources (rivers, lakes, etc.) can be regarded as a good indicator of the freshwater contamination [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. This work is aimed at determining the heavy metals status in surface and groundwater systems and its public health implication in the study area.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Study area\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eOsun River is located in southwestern Nigeria and is one of the key characteristics and features of Osun State (7.5629\u0026ordm;N, 4.5200\u0026ordm;E). The Osun River is situated in the southwestern part of Nigeria, primarily flowing through Osun and Oyo states. Osun River originates from Igede-Ekiti (in Ekiti State) and flows southwards through Southwestern Nigeria into the Lagos lagoon and the Atlantic Gulf of Guinea. Before flowing across Osogbo town in Osun State, the river meanders through many rainforests, farmlands and villages. The river flows across the southern part of Osogbo city (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) and serves as habitat to various fauna, especially catfish which are trapped and sold by local fishermen. The study areas covered the pre-urban and urban parts of the river. The sampling locations in this study have peculiar characteristics. Osun-jela is situated beside a bridge dividing Owode town with population of 83,831 (2006 census) from Osun-jela community (a rural settlement). It is about 25m from Osogbo-Ilesa road. Oke-ijetu (urban settlement) is beside a bridge along the newly constructed Oke-ijetu road with relatively less urban activities which is about 1km from Fountain University. This portion of the river accommodates some rocks, which form its base. Aregbe (urban settlement) is densely populated with anthropogenic activities, domestic and industrial wastes [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Sample Collection\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eWater samples were collected from surface water (Osun River) and groundwater (well) at Osunjela (7.739645\u0026deg;N 4.597762\u0026deg;E, 7.738606\u0026deg;N 4.596087\u0026deg;E and 7.737615\u0026deg;N 4.595897\u0026deg;E), Oke-ijetu (7.742508\u0026deg;N 4.556423\u0026deg;E, 7.743365\u0026deg;N 4.555888\u0026deg;E and 7.744362\u0026deg;N 4.555222\u0026deg;E) and Aregbe (7.767707\u0026deg;N 4.539669\u0026deg;E, 7.768203\u0026deg;N 4.539238\u0026deg;E and 7.768703\u0026deg;N 4.539010\u0026deg;E). Twelve water samples were collected from surface water (Osun River) and three water from groundwater (well) at Osunjela, Oke-ijetu and Aregbe each from upstream, midstream and downstream respectively from Osogbo town (Osogbo and Olorunda LGAs), Osun State, Nigeria in dry and wet seasons. The sampling was done for four months (March- June, 2024) because it was done at the peak of dry and wet seasons which corresponded with the peak of anthropogenic activities in the study areas. The samples were collected from upstream, downstream and midstream at a specific point respectively across the study area from the two sources [well (groundwater) and Osun River (surface water)] respectively monthly. Samples were transported to atomic absorption spectrophotometer laboratory (AAS), Centre for Energy Research and Development (CERD), Obafemi Awolowo University, Ile-Ife, Nigeria for further analysis [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e and \u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Digestion of water samples\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003e25ml each of the filtered samples were measured into clean conical flasks. 15ml of freshly prepared aqua-regia was added into each flask and were each heated to near dryness. 10ml of distilled water was then added and heated again for 2\u0026ndash;3 minutes, allowed to cool and filtered. The filtrates were each made up to mark in a 25ml flask and kept refrigerated pending metal determination by AAS [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e and \u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 CALIBRATION\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eBefore analyzing digested water, sediment and fish samples for metal concentration, PG990 AAS was calibrated with the use of standard reference material. Each of the metals has its own different standard concentrations which were prepared from the stock solution (1000ppm) for each cation.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5 Determination of cations (Heavy Metals) in water\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThe digested water samples was analyzed with PG990 atomic absorption spectrophotometer of the Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria for the heavy metals in the samples by flame atomization, using air-acetylene flame and single element hollow cathode lamp which generated absorbance values and concentrations for each of the heavy metals were generated automatically by software called AA win. This absorption follows Beer-Lambert\u0026rsquo;s law which states the absorbance to be directly proportional to the path length in the flame and to the concentration of atomic vapor in the flame [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e and \u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e2.6 Data Analysis\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eData analysis for the heavy metals involved processing and interpretation of the data generated from the Flame Atomic Absorption Spectroscopy (FAAS), using descriptive statistics.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eFifteen cations (Arsenic, Copper, Lead, Nickel, Iron, Zinc, Chromium, Manganese, Magnesium, Sodium, Calcium, Cadmium, Cobalt, Mercury and Potassium) were detected in the water samples from Osun River and selected wells from the study area. Thirteen cations with different concentrations were detected in both seasons {Arsenic (0.005 ± 0.003 to 0.018 ± 0.008mg/l), Copper (0.028 ± 0.023 to 0.058 ± 0.011mg/l), Cobalt (0.013 ± 0.001 to 0.028 ± 0.017mg/l), Lead (0.004 ± 0.004 to 0.016 ± 0.013mg/l), Nickel (0.014 ± 0.008 to 0.039 ± 0.008mg/l), Iron (0.021 ± 0.013 to 0.057 ± 0.005mg/l), Zinc (0.017 ± 0.004 to 0.047 ± 0.019mg/l), Chromium (0.011 ± 0.001 to 0.039 ± 0.001mg/l), Manganese (0.012 ± 0.012 to 0.025 ± 0.021mg/l), Magnesium (0.028 ± 0.004 to 0.070 ± 0.014mg/l), Sodium (0.018 ± 0.004 to 0.046 ± 0.006mg/l), Calcium (0.024 ± 0.003 to 0.044 ± 0.011mg/l) and Potassium (0.026 ± 0.014 to 0.060 ± 0.028mg/l) (dry season)} and Arsenic (0.004 ± 0.001 to 0.105 ± 0.002mg/l), Copper (0.036 ± 0.004 to 0.077 ± 0.011mg/l), Cobalt (0.003 ± 0.001 to 0.020 ± 0.013mg/l), Lead (0.004 ± 0.001 to 0.011 ± 0.003mg/l), Nickel (0.009 ± 0.001 to 0.037 ± 0.026mg/l), Iron (0.016 ± 0.006 to 0.067 ± 0.014mg/l), Zinc (0.021 ± 0.006 to 0.067 ± 0.004mg/l), Chromium (0.013 ± 0.002 to 0.043 ± 0.023mg/l), Manganese (0.016 ± 0.014 to 0.037 ± 0.040mg/l), Magnesium (0.034 ± 0.005 to 0.078 ± 0.018mg/l), Sodium (0.058 ± 0.042 to 0.096 ± 0.064mg/l), Calcium (0.023 ± 0.004 to 0.096 ± 0.064mg/l) and Potassium (0.035 ± 0.024 to 0.106 ± 0.023mg/l (wet season)} which were within WHO (2018) and EU (2020) limits. While Cadmium [(0.014 ± 0.008 to 0.035 ± 0.002mg/l) (Dry season)}; (0.012 ± 0.002 to 0.026 ± 0.003mg/l) (Wet season)] and Mercury [(0.005 ± 0.002 to 0.012 ± 0.012mg/l) (Dry season); (0.002 ± 0.000 to 0.080 ± 0.003mg/l) (wet season)] in Osun River and Wells exceeded 0.005mg/l according to WHO (2018) and EU (2020) limits (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and 3).\u003c/p\u003e\u003cp\u003e \u003cb\u003ea b\u003c/b\u003e \u003c/p\u003e\u003cp\u003ea b\u003c/p\u003e\u003cp\u003e \u003cb\u003eFigure 3: Concentrations of cations (heavy metals) analyzed from the surface water (Osun River) and groundwater (wells) in wet season\u003c/b\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe study revealed that the Osun River and Groundwater systems in Osogbo Town of Osun State, Nigeria were contaminated with fifteen cations (Arsenic, Copper, Lead, Nickel, Iron, Zinc, Chromium, Manganese, Magnesium, Sodium, Calcium, Cadmium, Cobalt, Mercury and Potassium) in Osun River and wells using Atomic Absorption Spectroscopy (AAS) where two cations (Cadmium and Mercury) were above 0.005mg/l according to the international limits {WHO (2018) and EU (2020)} limits in dry and wet seasons [14 and 15]. Adeyemi and Zacchaeus, (2021) determined the mean concentrations of eight cations (Nickel, Lead, Chromium, Manganese, Copper, Cadmium, Zinc and Iron) in groundwater (hand-dug wells and boreholes) collected from Ota and Sagamu industrial areas, Ogun State, Nigeria using Atomic Absorption Spectroscopy (AAS) where Lead and Iron exceeded the safe limits of WHO (2017) during dry and wet seasons [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Mustapha \u003cem\u003eet al\u003c/em\u003e. (2021) determined the mean concentrations of six cations (Zinc, Copper, Manganese, Iron, Lead and Cadmium) in Epe Lagoon, Lagos, Nigeria where Lead and Cadmium exceeded WHO (2003) safety limits [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe concentration of heavy metals in surface and groundwater systems in Osogbo metropolis were within safe limits according to international standards in dry and wet seasons, although there were slight seasonal variations across upstream, midstream and downstream. While, Mercury (Hg) and Cadmium (Cd) were observed to be high in concentrations above safety limits in both surface and groundwater systems in dry and wet seasons according to WHO and EU’s safety limits. This study showed that surface and groundwater systems assessed were contaminated with heavy metals in dry and wet seasons which portend health risks to consumers in the study area.\u003c/p\u003e"},{"header":"Recommendation","content":"\u003cp\u003eThere is a need for appropriate treatment of surface and groundwater systems before consumption by residents in the study area. Also, there is a need to regulate the activities of miners and residents that contribute to the contamination and pollution of these sources of portable water to forestall public health disasters in the study area.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCONFLICT OF INTEREST\u003c/h2\u003e\n\u003cp\u003eThere is no conflict of interest amongst the authors for this paper to be published.\u003c/p\u003e\n\u003ch2\u003eDATA DECLARATION STATEMENT\u003c/h2\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the study are available in a supplementary file.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eS. O. wrote the main manuscript text while the other authors reviewed the manuscript\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eI am deeply grateful to Professor Sidney Obidimma Nzeako from Department of Animal and Environmental Biology, University of Port Harcourt for his invaluable encouragement, motivation, inspiration, support, guidance and mentorship throughout this research.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eData is provided as a supplementary information file\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHarvey, J. W. \u0026amp; Bohlke, J. K. Contributions of stream water and groundwater to the chemistry of a praire stream, Konza Creek, Kansas, USA. \u003cem\u003eJ. Hydrol.\u003c/em\u003e \u003cb\u003e278\u003c/b\u003e (1\u0026ndash;4), 210\u0026ndash;225 (2003).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWinter, T. C. 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Concentrations and health risk assessment of industrial heavy metals pollution in groundwater in Ogun state, Nigeria. \u003cem\u003eSci. Afr.\u003c/em\u003e \u003cb\u003e11\u003c/b\u003e (1), 666 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMustapha, A. M., Ugya, A. Y. \u0026amp; Mustapha, Z. Assessment of heavy metals levels in fish tissues, water and sediment from Epe Lagoon, Lagos, Nigeria. \u003cem\u003eSci. World J.\u003c/em\u003e, \u003cb\u003e16\u003c/b\u003e(4). (2021).\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":"Groundwater, surface water, heavy metals, dry season, wet season, Osogbo","lastPublishedDoi":"10.21203/rs.3.rs-6127785/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6127785/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePortable sources of surface and groundwater are constantly polluted by anthropogenic activities and have negative impacts on human and animals\u0026rsquo; health. This study investigated seasonal variation of heavy metals in Osun River and selected wells in Osogbo town, Osun State, Nigeria, to ascertain their public health impacts. Water samples from surface and groundwater systems were examined using PG990 atomic absorption spectrophotometer to determine heavy metal concentrations of surface and groundwater systems in Osogbo town, Osun State, Nigeria. The concentrations of 13 heavy metals (Arsenic, Copper, Cobalt, Lead, Nickel, Iron, Zinc, Chromium, Manganese, Sodium, Magnesium, Calcium and Potassium) in well (groundwater) and surface water (Osun River) were within international limits except for Cadmium and Mercury which were observed to be above 0.005mg/l limits in dry and wet seasons. This study showed that the surface and groundwater systems assessed were contaminated with heavy metals in dry and wet seasons which portend health risks to consumers in the study area. Also, there is a need for appropriate treatment and regulation of the activities of miners and residents that contribute to the contamination and pollution of these sources of portable water to forestall public health disasters in the study area.\u003c/p\u003e","manuscriptTitle":"Determination of heavy metals in surface and ground water systems and its public health implication in Osogbo town, Osun State","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-16 11:25:50","doi":"10.21203/rs.3.rs-6127785/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":"14a4a1d8-2914-441b-a24e-1bbc800c9d16","owner":[],"postedDate":"April 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":47008014,"name":"Biological sciences/Ecology"},{"id":47008015,"name":"Biological sciences/Zoology"}],"tags":[],"updatedAt":"2025-04-25T09:23:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-16 11:25:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6127785","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6127785","identity":"rs-6127785","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}