Soil bacterial flora and enzymatic activities in zinc and lead contaminated soil

Soil bacterial flora and enzymatic activities in lead and zinc contaminated soil of Ishiagu, Nigeria were investigated. The physicochemical properties measured showed that the mining pit had acidic pH (5.6) which gradually increased till 7.5 in the control. Organic matter was only 2.57mg/g in the pit but gradually reached 7.41mg/g in control. Pb concentration was higher at pit 360.52mg/g, 305.46mg/g at 5m away and lowest at control 36.16mg/g. Zn was 217.47mg/g at the pit, 176.32mg/g at 5m, 106.18mg/g at 10m and only 40.67mg/g at control. This showed a gradual fall away from the pit. Major organisms at the pit were Pseudomonas and Bacillus species (30% each) and Mocrococcus and Chromobacter species (20% each) E. coli, Salmonella and Lactobacillus species, which occurred in the control soil, were absent in the pit soil but occurred at various rates in other soil samples. Bacterial prevalence, diversity, and bioload were all high in the control, followed by 100m away while values decreased significantly towards the pit. Soil enzymatic activities correlated negatively with heavy metal concentration. This showed that the higher the heavy metal concentration the lower the enzymatic activities. Urease, dehydrogenase activity, hydrogen peroxidase and polyphenol oxidase were adversely affected but alkaline phosphatase did not show any significant effect.