The Effect of Sewage Sludge and CdCl2 Application on Cadmium Transport in Soil and Plant Uptake
Subject Areas : environmental management
Keywords: Cadmium, sewage Sludge, transport and plant uptake,
Abstract :
The use of sewage sludge with high concentrations of heavy metals increases concentrations of these elements in soil, groundwater and food chain. This study investigated the effects of sewage sludge and CdCl2 application on Cd transport in soil and plant uptake. A filed experiment was carried out in a random block design with five treatments and three replicates (two levels of sewage sludge: 0, 50 ton ha-1 and three levels of Cd: 0, 42.5 and 85 mg Cd kg-1). Air-dried sewage sludge and CdCl2 were applied to soil and were mixed uniformly. In the first stage, cress was planted. Thirty days later, soil samples were collected from a 20-cm depth. Also, plant samples were provided from shoots and roots of cress. In the second stage, lettuce and spinach were planted. One hundred and eighty-four days later, soil samples were collected from 20, 40, 60, 80,100 and 120 cm depths. Plant samples were provided from shoots and roots of lettuce and spinach. The DTPA-Cd and total Cd concentrations were determined in soil samples. Also, Cd concentrations were determined in shoots and roots of plants. The results show that there existed a significant relationship between total Cd and DTPA-Cd in 20 cm depth after 30 and 184 days (R2=0.98 and R2=0.86, respectively ). CdCl2 application significantly increased the concentration of DTPA-Cd in the 20-cm depth. Sewage sludge and CdCl2 application had no significant effect on Cd transport in soil. CdCl2 application increased Cd concentrations in shoots and roots of plants significantly. Also, there were significant relationships between DTPA-Cd concentration and Cd concentration in roots of cress, lettuce and spinach (R2= 0.98, R2= 0.89, and R2= 0.76, respectively).