The influence of lead on the respiration and biomass of microorganisms in gray forest soil in a long-term field experiment

The effects of lead oxide and lead nitrate on soil microorganisms were studied in a field experiment. As soon as the soil was treated with lead, a response of the microbial community was expressed in the higher rate of the basal respiration irrespectively of the dose and form of the lead compounds applied. At the same time, the microbial biomass decreased in the variants contaminated with 100–1000 mg Pb/kg. The long-lasting influence of lead lowered the basal respiration and the microbial biomass in the variant with the application of 400–1000 mg Pb/kg in the form of nitrate and 1000 mg Pb/kg as oxide. The experiments proved that the content of mobile lead in the soil, irrespectively of the form and solubility of the lead compounds, controls the functional relationship between the effect of the lead and the microbiological indices of the soil. The suppression of the soil microbial activity by more than 25% took place when the mobile lead content exceeded 170 mg Pb/kg.