Abstract

This study investigated some physicochemical and heavy metals concentration in soils from around the bank of waste retention pits receiving municipal and industrial waste water from the vicinity of oil and gas facilities in Rivers state, Nigeria. Soil samples were collected during the rainy season month of June 2010 from the bank of two waste dump pits with one control sample being established 100 meters away from the waste point sources. The soils were collected and analyzed following standard field and analytical protocols. Results revealed the following soil characteristics: 6.08 – 7.53 (pH), 140 - 490 µS/cm (conductivity), 26.4 – 887.8 mg/kg (oil and grease), 1.05 – 1.66 mg/kg (ammonium), 85 – 320 mg/kg (chloride), 0.039 – 2.240 mg/kg (nitrite), 40.6 - 564 mg/kg (nitrate), 1.40 – 5.2 mg/kg (phosphate), 1.4 – 5.2 mg/kg (sulphate), 72.31 – 240.85 mg/kg (sodium), 27.20 – 78.5 mg/kg (potassium), 17.12 – 210.83 mg/kg (calcium), 13.94 – 41.19 mg/kg (magnesium), <0.01 mg/kg (mercury), 572.7 – 1,858.8 mg/kg (iron), 0.57 – 2.87 mg/kg (chromium), 0.01 – 0.130 mg/kg (cadmium) and 0.94 – 5.28 mg/kg (zinc). The waste pits showed an apparent enrichment in their various physicochemical attributes especially in waste pit 2. Therefore, the municipal and industrial waste water discharged in these pits could be contributing to an alteration in soil physical and chemical characteristics of the receiving environment since soils rich in organic matter actively retains metallic elements while the significant levels of toxic heavy metals and hydrocarbon in the control soil when compared to waste pit 1 may have resulted from the tendency of soils to retain persistent toxicants in an acidic environment since metal solubility tends to increase at lower soil pH. The elevated concentrations of oil and grease in the soils of waste bank 2 and control locations as compared to DPR target values also suggests that runoff from rainfall may have resulted in the transportation of organic constituents of improperly disposed municipal and industrial wastes into nearby surface or open water bodies depending on the retention time of the micro pollutants in the soil matrix and the relative topography of the area.



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