Effects of Phosphorus Solubilizing Bacteria on Chemical forms of Lead and cadmium in Two Different Textural Soils

One of the promising tools for evaluating heavy metals bioavailability in the environment is the knowledge of their partitioning among the various soil constituents. The present study was conducted in order to investigate the changes of chemical forms of cadmium (Cd) and lead (Pb) under the influence of phosphorus solubilizing bacteria in the soil.

Phosphorus (KH2PO4), Cd(NO3)2 and Pb(NO3)2 simultaneously were introduced into the soil to promote the contamination and formation of phosphate minerals of added metals in two selected soils. After two months the soils were inoculated with two Enterobacter species and incubated for 3 months. A single (DTPA) and sequential extraction scheme were applied to determine the chemical forms of Cd and Pb 5, 25, 60 and 90 days after incubation.

The results revealed that DTPA extractable Cd and Pb were decreased in the presence of the phosphorus solubilizing bacteria. Soluble+ exchangeable Cd fraction was decreased whereas, the fractions associated with organic matter and oxides were increased in inoculated soils during the incubation time. In the other hand Soluble+ exchangeable and carbonate fractions of Pb were increased and organic matter and oxides associated Pb fractions were decreased in the presence of phosphorus solubilizing bacteria. Carbonate and oxides associated are the abundant Cd and Pb fractions in studied soil.

Although the Cd and Pb chemical fractions were affected in the presence of phosphorus solubilizing bacteria, but two metals contradictory were differ in behavior in the studied soils. Indeed, the destination of added metals in the soil in the presence of microbes may be different.