Effects of Dumpsite Leachates on Soil Biological Sentinels in Benin City, Nigeria

Abstract

In this study, an attempt was made to examine the effects of dumpsite leachate on soil biological sentinels by collecting leachate samples from Ikhueniro and Otofure dumpsites in Benin City Nigeria, and analyzed using standard methods. The parameters include pH, chemical oxygen demand, biochemical oxygen demand, phosphate, sulphate, chloride, nitrate, chromium, cadmium and lead. The mean results showed pH (8.30 ±0.14), BOD (566 mg/l), COD (1713 mg/l), Phosphate (7.73 ± 0.14 mg/l), Sulphate (22.40 ± 0.75 mg/l), Chloride (187.5 ± 1.12 mg/l), Nitrate (1.47 V 0.06 mg/l), Chromium (0.06 ± 0.1 mg/l), Cadmium (0.20 ± 0.1 mg/l), Lead (1.03 ± 0.04) for Ikhueniro and pH (8.0 ± 0.1), BOD (315 mg/l), COD (1095 mg/l), Phosphate (5.85 ± 0.19 mg/l), Sulphate (31.70 ± 0.73 mg/l), Chloride (135.25 ± 1.59 mg/l), Nitrate (0.93 ± 0.09 mg/l), Chromium (0.06 ± 0.1mg/l), Cadmium (0.109 ± 0.1mg/l), Lead (0.015 ± 0.005 mg/l)for Otofure respectively. Different concentrations of leachate ranging between 25% and 100% was used and the growth of Nitrosomonas sp reduced from 6.4×10⁴(cfu/ml) – 2.9×10⁴(cfu/ml), when compared to the control which increased from 6.4×10⁴(cfu/ml) – 1.0×10⁵ (cfu/ml). The percentage survival of Lumbricus terrestris was 2.19%,  1.14%, 3.42%, 6.69%, with varying concentrations of 25%, 50%, 75%, and 100% respectively. The method implored for analysis shows the leachate sample was toxic to both test organisms. Nitrosomonas sp and Lumbricus terrestris may be used as indicator organisms for leachate toxicity in the soil.

Keywords: toxic leachate effects, heavy metals leachate, soil sentinels, earthworm assay