Phosphatase activity and populations of microorganisms from cadmium- and lead-contaminated soils.

摘要

A study was conducted to determine the effects of metals (e.g., Pb and Cd) and synthetic chelates (e.g., ethylenediamine tetraacetic acid (EDTA), ethylenebis (oxyethylenenitrilo), tetraacetic acid (EGTA)) on the phosphatase [phosphoric monoester hydrolases] activity and populations of bacteria and fungi from metal- and chelate-amended soils. It was observed that phosphatase activity decreased with increasing levels of soil Pb and Cd treatments compared to the control. This reduction in phosphatase activity was more pronounced in the presence of the chelates, EDTA and EGTA. Soil fungal population decreased with increasing levels of soil-applied Pb. It was noted however, that EDTA diminished the toxic effect of Pb especially at the lowest treatment. Soil fungi were tolerant to both Cd and EGTA as observed in their similar numbers compared to those present in the control treatments. Soil bacteria were tolerant to all levels of Pb except at 1000 mg Pb/kg treatment wherein a significant reduction in population was observed. Soil bacterial populations were greatly reduced by Cd especially at the two highest concentrations in combination with 5 mMol EGTA/kg. The resistance of the soil fungi and bacteria to soil-applied Pb and Cd indicated that these microorganisms have resistance mechanisms to deal with metal toxicity.