Comparing Bioavailability of Cadmium and Arsenic in Agricultural Soil Under Varied pH Condition

Bioavailability of cadmium (Cd) and arsenic (As) can be different depending on soil pH. For this reason, main purpose of this research was to compare bioavailability of Cd and As in agricultural field under varied soil pH and different extractants. Bioavailable fraction of Cd and As in soil was extracted with $CaCl_2$, $NaNO_3$, DTPA, EDTA, and low molecular weight organic acids (LMWOAs). Soil samples and cultivated crops were collected at the range of soil pH 4.5-8.5 and correlation analysis was conducted between bioavailable fraction of Cd and As in soil and total concentration of Cd and As in crops. Results showed that concentration of Cd and As in acidic soil was ranged $0.002-0.462mg\;kg^{-1}$ and $0.041-4.903mg\;kg^{-1}$ respectively. In alkaline condition, concentration of Cd and As were ranged $0.006-0.351mg\;kg^{-1}$ and $0.039-2.807mg\;kg^{-1}$ respectively. Comparing bioavailable fraction of Cd and As in acidic and alkaline soil condition, higher concentration was measured in acidic condition. Similarly, higher average concentration of Cd and Asin crops was observed in acidic condition (0.398 and $0.751mg\;kg^{-1}$ respectively) than alkaline condition (0.248 and $0.264mg\;kg^{-1}$). Among different extractants, LMWOAs method showed higher correlation ($r^2=0.545$) for Cd in acidic condition indicating that LMWOAs method could be applied for evaluating bioavailability of Cd in acidic soil. However, no high correlation was observed for As in both acidic and alkaline condition. Overall, bioavailable fraction of Cd and As can be higher in acidic condition of soil than alkaline condition resulting higher uptake of Cd and As from soil to crops. Therefore, efficient best management practice (BMPs) for Cd and As in acidic soil should be conducted for minimizing uptake of Cd and As into crops.