Impact of zinc and lead on soil respiration and microbial content under in vitro conditions

The habitation and activities of soil aerobic bacteria living in the sandy clay soil were affected by the toxicity of Zinc and Lead ions at different levels. Their inhibitory effect was manifested directly in the decrease of the total aerobic bacteria counts in the soil and physiological activity of the soil aerobic bacteria. Aerobic bacteria population generally decreased similarly to the CO₂-production in response to the toxic effects of the investigated metal ions. The soil samples were metabolically activated by C,N and P in the form of sodium nitrate, potassium phosphate and glucose, respectively as substrate-induced respiration. The inhibitions of biological activities in the soil samples were appeared even after three weeks, but highly significant effects were obtained after six-week incubation period. Lead had smallest effects on decreasing CO₂-production at different incubation intervals. The strongest inhibition of the gas production was detected by the influence of Zinc ions.