Effect of Cadmium and Lead Concentrations on Their Bioavailability in Different Soils

mouseover=«function onmouseover() {msoCommentShow (''_anchor_1''،''_com_1'')}» onmouseout=«function onmouseout() {msoCommentHide (''_com_1'')}» href= «#_msocom_1» > [H1] The objective of this study was to investigate the effect of time and concentration on bioavailability of added Cd and Pb to one acidic and three alkaline soils. The soils were treated with five different concentrations of Cd and Pb and incubated at 85% field capacity and constant temperature of 25 ° C for one year. Samples were taken at certain intervals and extracted by DTPA method. Results showed that decrease in Cd and Pb bioavailability were initially rapid followed by a slower rate at longer time. Time dependence of Cd and Pb bioavailability in different concentrations had a similar pattern، except for 5000 mgPb kg-1. After one year، the bioavailability of soil-added Cd and Pb decreased 50. 4% and 57 % in alkaline soils and 35. 4% and 42% in acidic soil، respectively. bioavailability increased with increasing soil-added Cd and Pb levels، but this increase was linear for Cd and nonlinear for Pb. Comparison of coefficients of determination (R2) showed that the modified Probert- Larsen equation was able to describe the results (R2=0. 92 to 0. 99، p<0. 001).