Abstract

In this study, remediation of heavy metals; arsenic, cadmium, chromium, copper and lead, and petroleum hydrocarbons in co-contaminated soil using in situ application of admixtures of poultry manure and termite mound soil was examined. The contaminated soil with total heavy metals content, MTot 110.69±3.08 mg.kg-1 (As 8.00±0.36 mg.kg-1; Cd 10.83±0.33 mg.kg-1; Cr 20.90±0.56 mg.kg-1; Cu 43.43±0.99 mg.kg-1 and Pb 25.45± ±0.85 mg.kg-1) and total petroleum hydrocarbons content 208.30±0.62 mg.kg-1 was treated with admixtures of poultry manure and termite mound soil of various compositions (0 – 100 wt% poultry manure) and durations (30 – 120 days) of amendment application. Reductions in the levels of total-extractable and bioavailable metal fractions and in residual total petroleum hydrocarbons, plant (maize) uptake and transferability of heavy metals and changes in soil enzyme activities were used as indicators of remediation end-point. It was found that in comparison with unamended soil, marked reductions (in the range 64 -89%) were associated with poultry manure/termite mound soil application to the contaminated soil. The reduction in bioavailable metal fraction following amendment application was reflected in corresponding reduced plant uptake, 18-fold by maize roots and 25-fold in transferability to maize shoots as a result of the application of poultry manure/termite mound soil to the contaminated soil. Degradation of petroleum hydrocarbons varied in apparent dependence on the poultry manure content of the amendment and was almost quantitative (95%) with application of amendment (100 wt% poultry manure) and duration of 120 days. Increased levels of soil enzyme activities of several order of magnitude (67 – 500%) in comparison with unamended soil accompanied application of poultry manure/termite mound soil amendment to the contaminated soil. Restoration of soil quality (measured in terms of enzyme activities) depended on the level of poultry manure component of the amendment material.

Keywords: : contaminated soil, remediation, amendment application, metals, petroleum hydrocarbons