Studies of common heavy metals were conducted at Onitsha, Anambra State, the most urbanized city in Southeastern Nigeria. It was discovered that both surface and subsurface water were heavily polluted. Seven (7) heavy metals namely: arsenic (As +2), cadmium (Cd +2), lead (Pb +2), mercury (Hg +2), zinc (Zn +2), copper (Cu +2) and iron (Fe +2) were studied. Their major sources include wastes like refuse dumps, effluent from industries, sewage, fuel spills from dumps and mechanic workshops, hospital and pharmaceutical wastes, agricultural materials, fossil fuel combustion, metallurgical industries, electronic components and semiconductors , batteries, pigments and paints. Further data were collected in ongoing research works in the area and public enlightenment was done in a small scale. Recommendations are made to government to note the impending dangers of further urban environmental pollution by these trace metals.

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Mining activities have long been recognized as a major source of environmental contamination associated with heavy metals and metalloids. This study evaluated the relationship between the occurrence and mining of lead-zinc sulphide ores at Ishiagu, Nigeria, and heavy metal and metalloid contamination. A comparative study of two zones in the area, with and without mining activities was also made Water, soil, stream sediment and ore samples were analyzed, after acid digestion, using atomic absorption spectrophotometer (AAS).  The concentration levels of seven heavy metals and a metalloid namely Pb, Cu, Ni, Zn, Mn, Co, Cd and as were evaluated. While the highest concentration levels of As, Co and Pb (5.20 mg/l, 0.54 mg/l and 3.40 mg/l respectively) were found in water, those of Ni and Mn (2.26 mg/l and 5.48 mg/l respectively) occurred in soil.  For Cu and Zn, highest levels of concentration (2.80 mg/l and 0.41 mg/l respectively) occurred in stream sediments. The variations in the concentration levels of these elements in varying geologic media (soil, water and sediment) indicate influence of rock types, human activities and media physiochemical characteristics. Geostatistical analyses using QQPlot, semivariogram and kriging showed normal distribution of these elements. Distribution and dispersion patterns of the heavy metals indicated increase in concentration levels in the local stream flow direction. Pb, Cu, As, Cd, Mn, and Ni concentrations had reached pollutant levels in water based on WHO standards, while Zn level is below. Since the local people use untreated surface water and groundwater for drinking and other domestic purposes, soil for farming and lead for cosmetics, long term exposure poses significant health risk for humans, animals and plants.

Pollutants have a tendency to sequestrate into remote sites in different environmental matrices thereby reducing the level of available fraction for uptake in living organisms. We examined availability of metals by subjecting soil and rice plant samples from Ishiagu mining district to a sequential extraction procedure and subsequently analyzed the extracts using Atomic Absorption Spectrophotometer (AAS). Our results revealed that metals were moderately available in samples in the following decreasing order: Zn>Pb>As>Cd>Se>Cu. Though metal levels differed in rice plant samples compared to soil, we noted also that availability of these pollutants varied spatially among various study locations. Based on available acceptable range, copper and zinc were within tolerable limits while cadmium was in excess in some study locations. On the other hand, levels of lead in rice plant samples exceeded acceptable limits. Considering the levels reported from different locations, it is possible that metals were immobilized in soil organic matter or trapped in other forms. Though in general metal levels were within acceptable limits in our study locations, we recommend that deliberate steps be taken by authorities to curtail indiscriminate mining activities capable of polluting soils and farm lands. For this reason, farmers should be encouraged to plant safe cultivars since this rice variety is a known poor metal accumulator.