Toxicologie environnementale et analytique

Evaluation of Leachate Contamination Index Obtained from Dumpsite in Onitsha, Nigeria

Abstract

Emmanuel Ikpe Michael

Physico-chemical and microbiological parameters were analyzed in leachate sample obtained at different locations (Obosi public dumpsite, groundwater and agricultural soil farmland 45.6 km from Onitsha dumpsite). This is to assess the impact of leachate and the effect of heavy metals on agricultural produce, Zea mays and Phaseolus vulgaris. In addition, pH values and the concentrations of these metals (Cd, Ag, Al, Mo, As, Hg, Mn, Zn, Cu, Hi, Cr, Mg, Fe, Pb and Co) in dumpsite leachate, agricultural soil collected from a depth of 10 cm were assessed. The pH of the experimental samples ranged from 6.41-7.15. The analysis of samples for heavy metals revealed very high concentrations of Mg (14.20-20.23 ppm), Hg (0.002-2.29 ppm), Pb (0.09-0.65 ppm), Cd (0.001-0.53 ppm), but Al and As were not detected in most of the samples. Physiochemical parameters (Total dissolved Solid, Temperature, Conductivity, Turbidity, Cation Exchange Capacity, Color, Total Organic Carbon and Particle size) and Microbiological parameters (Total heterotrophic bacterial and fungal count) were analyzed using standard methods. The microbial enumeration showed heterotrophic bacterial and fungal count ranging from 12 × 105 to 2 × 105 cfu/ml for leachate and ground water samples. Heterotrophic fungal count ranged from 3 × 105 to 8 × 105 cfu/ml for leachate and ground water. Culture plate, structural form and biochemical characterization conducted on these isolates using Bergey's manual of determinative bacteriology. Fungal atlas was used to suggest possible identities of the fungal isolates. These isolates were molecularly identified by 16 S rDNA and ITS rDNA sequence analysis for bacterial and fungal isolates respectively. The bacterial identities were Lysinibacillus fusiformis and Klebsiella pneumoniae, while fungal isolates were identified as Aspergillus tamarii, and Aspergillus fumigatus. The leachate generated from Obosi overburden dumpsite has the potential to pollute the surrounding water.