Study and Assessment of Trace Metal Contamination (As, Cd, Pb and Hg) in Water Resources from the Headwaters of the Ouémé and Pendjari Watersheds in the Copargo Municipality, Northwestern Benin

<p>Understanding the geochemistry of water resources is a prerequisite in the development of sustainable water resource management strategies. The Pra Basin is one of the few basins in Ghana with economic importance. The Basin is constituted by three river systems (Birim, Offin and Pra) and covers a total land size of approximately 2,300 km<sup>2</sup>. It traverses several towns and serves as the main water supply for communities and industry. Currently, the quality of water resources in the Pra Basin especially surfacewaters have been affected negatively as a result of activities such as illegal mining (e.g., the use of mercury for the extraction of gold), indiscriminate waste disposal, and poor farm management practices (e.g., inappropriate application of fertilizers and pesticides). Specific contaminants include mercury (Hg), arsenic (As), lead (Pb), iron (Fe), manganese (Mn), cadmium (Cd), selenium (Se), and nitrate (NO<sub>3</sub>). The Pra Basin is underlain by three rock formations, the Birimian Supergroup, the Tarkwain Formation and the granitoids. The mineral composition of the Birimian Supergroup comprises argillitic/pellitic sediment (plus or minus kerogen), sericite schist, and quartz-sericite schist. The granitoids comprise biotite (hornblende, muscovite), biotite gneiss, biotite schist, amphibolite partly of contact metamorphism, K-feldspar rich granitoid, two-mica or muscovite granite and monzonite, serecite schist, quartz-serecite, and garnet. The Tarkwaian rocks mineralogy also includes basaltic flow/subvolcanic rock and minor interbedded volcaniclastics, detrital sediment mainly sandstone and conglomerate ultramafic and minor mafic igneous rock. Samples of groundwater were collected from shallow (mainly hand-dug wells of depths < 10 m) and deep (mainly boreholes of depths >30 m) aquifers across the Pra Basin. Surfacewaters were collected from rivers and stream networks.  The samples were analysed for major ions, trace metals and stable isotopes (oxygen-18 and deuterium) using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Ion Chromatography (IC), and Picarro L-2140i Ringdown Spectrometer at the GFZ laboratories. Multivariate statistical analysis and inverse geochemical modelling have been applied to around 100 water samples sourced from boreholes, hand-dug wells, and rivers of the Pra Basin to determine the chemical state of the waters. Specifically, the study seeks to (1) determine the origin and evolution of the geochemistry of both surfacewater and groundwater, (2) identify recharge and discharge areas, and (3) study sources and sinks of minerals including sulphates, carbonates, and silicates. The abundance of cations and anions are in the order of Na>Ca>K>Mg and HCO<sub>3</sub>>Cl>SO<sub>4</sub>>NO<sub>3</sub> (surfacewater), Na>Ca>Mg>K and HCO<sub>3</sub>>Cl>NO<sub>3</sub>>SO<sub>4</sub> (hand-dug well), and Na>Ca>Mg>K, and HCO<sub>3</sub>>Cl>NO<sub>3</sub>>SO<sub>4</sub> (boreholes). Our research findings demonstrate that geochemistry of water resources in the Pra Basin is mainly controlled by rock-water interaction. With the application of hydrogeochemical modelling, including silicate mineral weathering and ion exchange, significant processes controlling the basin’s hydrochemistry variations are quantified. The presented results will support the development of sustainable water resources management strategies and contribute to mitigating future contamination.</p>

<p>As the demand for water supply increases with population growth, the quality of ground and surface water resources is deteriorating rapidly in many regions worldwide, particularly in Ghana. This situation has put supply systems under severe pressure as many of the available water resources are polluted by anthropogenic activities such as mining, agriculture, domestic and industrial sewage. Ghana's water quality problems are not different from current global challenges, as many surface waters and some aquifers have been polluted by mining activities and to some extent also by agriculture and industrial seepage. The Pra Basin is one of the most affected basins in Ghana with a total area of around 2,300 km<sup>2</sup> and a population of over five million people. The economic history of the basin is unparalleled as it is home to the country's major mineral deposits, including gold, bauxite, manganese, and diamonds. Recent studies have shown significant amounts of water pollutants including mercury (Hg), arsenic (As), lead (Pb), iron (Fe), manganese (Mn), cadmium (Cd), selenium (Se) and nitrate (NO<sub>3</sub>). The underlying geology of the Pra Basin consists mainly of metasediments and granitoids. The occurrence of groundwater is controlled by the development of secondary porosities through fractures, joints, and faults. This study provides insights into the evolution and hydrogeochemical processes that control the groundwater quality in the Pra Basin. The methodology applied here includes field sample collection, statistical analysis of hydrochemical data, petrographic and mineralogical analysis of rock outcrops and geochemical modelling. Groundwater samples were taken from shallow (mainly hand-dug wells with depths <10 m) and deep aquifers (mainly boreholes with depths >30 m) throughout the basin. Samples were analysed for major ions, and trace metals using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Ion Chromatography (IC), and a Picarro L-2140i Ringdown Spectrometer. Multivariate statistical analyses, inverse and forward geochemical modelling were applied to the hydrochemical data of around 100 water samples. The mineral phases used as model input were obtained from X-ray Diffraction (XRD) measurements of rock outcrops from the study area and mainly include chlorite, albite, muscovite, biotite, and calcite. The analysis of the results shows that the geochemistry of the groundwater resources in the Pra Basin is mainly controlled by water-rock-interaction. Within the given uncertainty limits, the dissolution of carbonates and weathering of silicates are the drivers for the chemical development of the groundwater in the basin. The presented findings will support the development of sustainable water resources management strategies and contribute to mitigating future contamination.</p>

Most regions in the tropics undergo high seasonal precipitation that produces cyclic patterns of riverine discharge, resulting in periods characterized by low and high water levels. Many chemical and bio-logical factors are affected by this hydrologic seasonality, and it therefore appeared to be very likely that aquatic food webs would also differ during the low and high water periods. Available carbon sources for fish are thought to be less varied during low water periods, but flooding during high water periods could bring fish into contact with a greater abundance and diversity of food sources such as terrestrial plants or the biofilms that grow on submerged terrestrial plants. At low water levels, higher fish densities may lead to more piscivory and less omnivory when compared with the high water periods. Therefore, trophic links within the fish communities may then be modified by water level changes in tropical reservoirs. To address this prediction, we performed stable isotope analyses of the most common species in Sélingué and Manantali, two large reservoirs in Mali (West Africa). Allochthonous and littoral carbon sources were shown to support fish production to a significant extent, even during low water periods. However, the allochthonous or littoral carbon contributions that sustained the top-predators production were indeed greater during the high water periods as expected. The expected higher omnivory in the high water period might have shortened the food chain when compared with the low water period. Some carnivorous fish species were shown to feed at lower trophic levels during high water periods in both reservoirs, but this was not a general pattern. Flooding did not, therefore, necessarily result in a shorter food chain when water levels were high. § Revised version of a paper presented at the 4th International Conference on Applications of Stable Isotope Techniques to Ecological Studies, April 19–23, 2004, Wellington, New Zealand.

The objectives of this study are to investigate chromosomal aberrations of snakehead fish in a leachate-affected reservoir located 100 meters from a municipal landfill which compared to non-affected reservoir. Three snakehead fish were collected and chromosomal aberrations were studied using kidney tissue. Lead and mercury were measured in water, sediment and snakehead fish from the affected reservoir at three sampling sites. The results showed that the average concentrations of lead and mercury in water were 0.0012±0.0003 and 0.0053±0.0036 mg/L, respectively. The average concentrations of lead and mercury in sediment were 3.3650±2.1930 and 0.0890±0.0272 mg/kg, respectively. These values did not exceed the standard for water and soil quality except for the mercury in the water, which was higher than acceptable. Lead was not found in snakehead fish from either reservoir. The average concentrations of mercury in snakehead fish from both reservoirs were 0.1330±0.0792 and 0.1180±0.0350 mg/kg, respectively, which were higher than the standard for mercury contamination in food. This study showed that the accumulation of mercury in snakehead fish was higher than in sediment because it accumulates in organisms through the consumption hierarchy. The diploid chromosome number of snakehead fish in both reservoirs was 2n = 42 and the percentage of chromosomal breakages of snakehead fish in the affected reservoir was higher than the non-affected reservoir. There were four types of chromosomal breakages: single chromatid gap, isochromatid gap, single chromatid breaks and isochromatid breaks. The difference in percentage of chromosomal breakages in snakehead fish from both reservoirs was statistically significant (p<0.05).

Water quality studies in Nigeria are usually conducted at local scales and limited to a restricted number of chemical contaminants, while reliable data on trace metal concentrations (including arsenic) are relatively scarce. This study focuses on the quality of available renewable water resources in terms of major ion and trace element concentrations at selected sampling locations in the Lower River Niger basin and part of the Lagos region. A screening of water contamination by arsenic and heavy metals was carried out through water sampling at selected locations using in situ measurement and laboratory testing to estimate heavy metal concentrations and water type. The analysis reveals moderate trace element contamination of the water resources, with the exception of Pb, while Mn and, to a lesser extent, Al exceeded WHO quality standards, but the Arsenic concentrations are within drinking water quality standards and are safe for consumption and irrigation, while the water type is Bicarbonate.

Water resources assessment of zayandeh-rood river basin using integrated surface water and groundwater footprints and K-means clustering method

This study aimed to evaluate the concentration of heavy metals, specifically cadmium, mercury, lead, and arsenic, in locally produced food from the Arkhangelsk region and other regions of Russia. Data on the content of heavy metal were studied in accordance with the protocols of the Center for Hygiene and Epidemiology in the Arkhangelsk Region and the Nenets Autonomous Okrug during the period of 2017-2022. The levels of heavy metals did not exceed the maximum permissible concentrations. The analysis of median concentrations of heavy metals in food products produced in the Arkhangelsk region found that bread products had the highest average concentrations of cadmium and lead, while fish and fish products had the highest average concentrations of arsenic and mercury. The lowest average concentrations of cadmium and arsenic were found in fat-containing products, while milk and dairy products had the lowest average concentrations of mercury and lead.

This article is devoted to the study of the main environmental problems of local areas, which are associated with anthropogenic pressure on the quality of water and land resources. The scientific novelty of the work is identified the specific ecological factors which influence on the local areas and analyzed the cause deterioration of water and land quality. The research program provided for the application of a systematic approach to determine the main aspects of anthropogenic pressure on the state of local areas in order to evaluate the impact of urbanization and agricultural activities on land and water resources. To implement the research program, the following tasks were: to determine the factors influencing urbanization and agricultural activities on the state of land and water resources of local areas, which causes a significant anthropogenic load on the territory; to study the main factors of pollution of local areas due to anthropogenic load. According to the results articles we analyzed and determined the main environmental factors which had affect and influence on the quality water and land resources of local territories (Kyiv and Khmelnytsky regions). In particular, it was clarified that the main factors deteriorating the quality of water resources were discharges of untreated wastewater from enterprises and filtration water from landfills, which, due to technological violations, came from landfills to riverbeds. The anthropogenic pressure on land resources is due to the agricultural sector, in particular, it was found that uncontrolled use of agrochemicals and untreated manure in the studied areas were a predictable risk factor for soil contamination by pathogenic bacteria and heavy metals.

Hydroperiodic dynamics of microbial-mediated nitrogen cycling and its multi-element coupling effect in the Weihe River.

This work was carried out to monitor contamination levels of twelve heavy metals (HMs) in the agricultural soils of Kafr El-Zayat city in Egypt. The concentrations of Mg, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, and Pb were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). Contamination levels were estimated based on various geochemical parameters such as contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), degree of contamination (Cd ), and pollution load index (PLI). The results showed that the majority of investigated soil samples were moderately contaminated (1 ≤ CF < 3) with V, Cr, Co, Cu, Zn, and Sr and had low contamination levels (CF <1) with Mg, Mn, Fe, Ni, and Pb. All investigated elements had geo-accumulation indices smaller than zero indicating uncontaminated soil samples except for V which showed (0 < Igeo < 1) indicating uncontaminated to moderate pollution levels. All soil samples were found to have deficient to minimal enrichment for all investigated HMs based on the average values of EF (EF < 2). Cluster analysis (CA) and principal component analysis (PCA) revealed that HMs were clustered into three groups compromising As and V; Ni, Cr, Mn, Co, Fe, and Mn; and Pb, Cu, Sr, and Zn, which suggests the presence of different sources of pollution. The contribution of anthropogenic sources to V, Cr, Co, Cu, Zn, As, and Sr was estimated to be 45, 30, 26, 11, 23, 27, and 13% of the total metal content, respectively. In general, the investigated agricultural soil samples could be classified as moderately contaminated and polluted based on the Cd factor (Cd = 13.7), and the PLI (PLI = 1.1), respectively.

Nokoué Lake is located in the south of Benin and is fed by the Ouémé and Sô Rivers. Its hydrosedimentary dynamics were modelled using Telemac2D, incorporating the main environmental factors of this complex ecosystem. The simulations accounted for flow rates and suspended solids concentrations during periods of high and low water. The main factors controlling sediment transport were identified. The model was validated using field measurements of water levels and suspended solids. The results show that the north–south current velocity ranges from 0.5 to 1 m/s during periods of high water and 0.1 to 0.5 m/s during low-water periods. Residual currents are influenced by rainfall, river discharge, and tides. Complex circulation patterns are caused by increased river flow during high water, while tides dominate during low water and transitional periods. The northern, western, and south-eastern parts of the lake have weak residual currents and are, therefore, deposition zones for fine sediments. The estimated average annual suspended solids load for 2022–2023 is 17 Mt. The model performance shows a strong agreement between the observed and simulated values: R2 = 0.91 and NSE = 0.93 for water levels and R2 = 0.86 and NSE = 0.78 for sediment transport.

Aim: We aimed to evaluate the variation in planktonic ciliate species composition in different strata of the Guaraná Lake, encompassing high and low water periods, at the Upper Paraná River floodplain. Methods Samplings were collected monthly between March 2007 and February 2008, from the epilimnion, metalimnion and hypolimnion. Ciliates samples were filtered using a plankton net of 10µm mesh size and identified in vivo under an optical microscope. Results Among 112 species identified, 13 were found exclusively during the high water periods and 39 during the low water period. Results of nonparametric extrapolation indices evidenced that the observed richness represented between 70% and 90% of the estimated richness. Regarding the variation in species composition, Beta1 index showed that the alteration in composition between strata during the low water period was slightly greater than that registered during high waters. Cluster analysis evidenced a higher dissimilarity in ciliate species composition between periods than among the different strata. The greatest variation in species composition was verified during the distinct hydrological periods, whereas no significant differences were observed for the different strata analysed. Conclusions We found that in the pelagic compartment, ciliate species composition changed significantly between hydrological periods, and a higher similarity in species composition among strata was observed during the high water period. Therefore, alterations in the vertical distribution seem to be related to the homogenizing effect of the floods in the water column stability.

Integrated LIBS-Raman spectroscopy: A comprehensive approach to monitor microplastics and heavy metal contamination in water resources

From South African and international experience, it is known that coal mining has a pronounced impact on surface and groundwater quality and quantity. The influx of water may be as low as 1% of rainfall for underground mines to as much as 20% for opencast mines. Such differences may influence the quantity and quality of surface water and groundwater resources at the local scale and further afield. The Waterberg coal reserves represent the only area with proven coal reserves which are still available for development in South Africa. These reserves are targeted for large-scale mining in the near future, and are situated in a relatively dry part of South Africa. In view of the low rainfall and limited surface water resources, the necessary level of safeguard measures to ensure the quantity and quality of existing water resources is unclear. Experience from other areas cannot necessarily be extrapolated directly. A scoping level study was performed to consolidate the existing information on the geohydrology and pre-mining water quantity and quality of water resources associated with the Waterberg coal reserves. New data regarding water quality and acid-base potential for the different geological areas (through field investigations) and geology and mining methods were obtained. Findings showed a significant likely impact on groundwater resources, with a potential for generation of acid mine drainage, although low transmissivities will in all probability prevent decant after back-filling is complete.Keywords: Waterberg Coalfield, water quality, water quantity, recharge, acid-base accounting, geohydrological modelling

We examined the life history, annual production, diet, habitat preferences and competition of two species of stoneflies Notoperla fasciata and N. magnaspina in a Patagonian mountain headwater stream. Benthic samples and adult collections were taken monthly from July 2004 to June 2005. A habitat selection study was performed concurrently during high and low water periods in five substrate types. Although both species showed long life cycles (N. fasciata: 20 months and N. magnaspina: 3 years) their life histories and temporal dynamics were different. Growth was rapid during summer and early autumn as a result of warmer temperatures but N. magnaspina had a shorter emergence period (November to January) than N. fasciata (January to April). N. fasciata was the dominant Notoperla species with a mean annual density 6 times higher and secondary production 4.5 higher than that of N magnaspina. While boulders in riffles and pools, and leaf-pack habitats supported significantly more individuals of N. magnaspina in the low water period (ANOVA, p 0.26). N. fasciata dominated in the high water period and N. magnaspina during the low water period. Analysis of gut contents revealed that both species were herbivorous grazers, and consumed the same food types. The interspecific overlap in density, biomass and annual production among habitat types was high in the low water period (PS> 0.5). However, N. fasciata were smaller than N. magnaspina. The existence of different life history strategies and the temporal shift of main generations and density peaks were critical to allow species coexistence and to reduce competition.