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Water chemistry in the shale bedrock of the Cretaceous-Tertiary of the Cross River and Niger Delta hydrological basins has been investigated using major ions. To carry out a characterization of the water bearing units, 30 and 16 representatives surface and groundwater samples were collected. The evolution of the water is characterized by enhanced content of sodium, calcium and sulphate as a result of leaching of shale rock. The spatial changes in groundwater quality of the area shows an anomalous concentrations of ions in the central parts, while lower values characterize the eastern part of the basin covering Ogoja, Ikom and Odukpani areas. The values of total dissolved solids (TDS) and ions increases down gradient in the direction of groundwater flow. The dissolution of halite and gypsum explains part of the contained Na ? , Ca 2? , Cl -and SO 4 2-, but other processes such as ion exchange, silicate weathering and pyrite oxidation also contribute to water composition. The assessment with contamination indicators such as TDS, hardness, chloride, nitrate and sulphate indicates that the water in area is suitable for human consumption in some locations. Modelling using MINTEQA2 program shows that the water from all the shale water bearing units are under saturated with respect to gypsum.

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A detailed investigation was conducted on the relationship between land use patterns and trace metal content in surface soils of the Benue State to assess soil environmental quality. Results revealed that metals levels were generally high in mineralized and urban soils and lower in agricultural soils whilst forest soils were lease by anthropogenic pollution. Mineralized soils developed from weathered sulphides were rich in lead (Pb), zinc (Zn), and cadmium (Cd). Urban soils accumulated copper (Cu), Zn, and Cd most probably from refuse dumps, gasoline combustion and farming. Agricultural soils were enriched in arsenic (As) and to a lesser degree Pb and Cd originating most probably from the application of pesticides, manure and fertilizers. A pollution index (PI) based on plant-tolerant contamination levels, indicates that multi-element contamination in soils is low and implies that the sampled soils could be cultivated for crop production especially away from point sources of pollution. The degree of anthropogenic pollution was high for As (80%), and Pb (54%), moderate for Zn (47%), Cd (40%), and low for Cu (27%). Correlations (r) are significant between Zn-Pb (0.7), Cu-As (0.6) in mineralized soils, between Zn-Cu (0.64), Zn-Cd (0.5), Cu-Cd (0.6), in urban soils, As-Cd (0.61), in agricultural soils and Zn-Pb (0.82) in forest soils. These distinct relationships indicate a common source or similar geochemical control. Based on the overall evaluation, recommendation in respect of contamination, control and monitoring strategies as well as land use planning in the study area are presented.

Water, sediment, and mine spoil samples were collected within the vicinity of the Okpara coal mine in Enugu, Southeastern Nigeria, and analyzed for trace elements using ICP-MS to assess the level of environmental contamination by these elements. The results obtained show that the mine spoils and sediments are relatively enriched in Fe, with mean values of 1,307.8(mg/kg) for mine spoils and 94.15% for sediments. As, Cd, Cr, Mn,Ni, Pb, and Zn in the sediments were found to be enriched relative to the mean values obtained from the study area, showing contamination by these elements. The mean values of Fe, Mn, Cu, and Cr in the mine spoils and mean values of Fe, Cu, Pb, Zn, Ni, Cr, and Mn in sediments, respectively, are above the background values obtained from coal and shale in the study area, indicating enrichment with these elements. The water and sediments are moderately acidic, with mean pH values of 4.22±1.06 and 4.66±1.35, respectively. With the exception of Fe, Mn, and Ni, all other elements are within the Nigerian water quality standard and WHO limits for drinking water and other domestic purposes. The strong to moderate positive correlation between Fe and Cu (r=0.72), Fe and Zn (r=0.88), and Fe and As (r=0.60) at p<0.05 as obtained for the sediments depict the scavenging effect of Fe on these mobile elements. As also shows a strong positive correlation with Mn (r=≥ 0.70, p<0.05), indicating that Mn plays a major role in scavenging elements that are not co-precipitated with Fe. In water, the strong positive correlation observed between Cr and Cd (r=1.00), Cu and Ni (r=0.94), Pb and Cu (r=0.87) and Zn and Cu (r=0.99); Ni and Pb (r=0.83) and Zn and Ni (r=0.97); and between Pb and Zn (0.84) at p<0.05 may indicate similar element-water reaction control on the system due to similarities in chemical properties as well as a common source. Elevated levels of heavy metals in sediments relative to surface water probably imply that sorption and co-precipitation on Al and Fe oxides are more effective in the mobilization and attenuation of heavy metals in the mine area than acid-induced dissolution. The level of concentration of trace elements for the mine spoils will serve as baseline data for future reference in the study area.