Application of phosphorus fertilizers to a multi-element contaminated soil resulted in increased water soluble As, but decreased As uptake by plants

摘要

A field trial using a vegetable (Brassica campestris L. chinensis) was conducted in a heavy metal and arsenic (As) contaminated soil (Alfisol) in Shaoxing, China, to evaluate the effectiveness of phosphate fertilizers including single super phosphate (SSP), phosphate rock (PR) and calcium magnesium phosphate (CMP) in immobilization and mobilization of heavy metals and As;to investigate the dynamics of heavy metals and As after application of SSP, PR and CMP;and to elucidate the relationship among P, As and Pb in relation to their uptake by the vegetable. Results showed that SSP treatments decreased soil pH, while PR and CMP treatments increased soil pH. Water soluble As increased with the increase in pH. Water soluble P increased significantly with applicatiou rates in the order SSP ?CMP?PR. P fertilizers decreased water soluble Pb except SSP2 and SSP3. It is ap-parent that lower pH and higher Ca concentration in solution increased Pb availability. Ca is an important ion influencing availability of Pb Zn and As in soil solution, leading to competitive absorption by the vegetable. It was found that water soluble As concentration was positively correlated with water soluble P. Pb concentrations in the vegetable in all P applied plots were lower than the controls, even in SSP2 and SSP3 plots in which water soluble Pb concentration was much higher than the controls. Therefore it is suggested that higher uptake of Ca suppressed Pb uptake by the vegetable. The correlation coefficient (r=0.785 **) between Pb and Ca in the vegetable indicates that Ca plays an important role in Pb uptake by the vegetable when P fertilizers are applied to immobilize Pb in contaminated soils. P concentration in the vegetable was negatively correlated with As concentration (r=- 0.813 **), suggesting that P suppressed As uptake by the vegetable even though water soluble As in the soil solution significantly increased by up to 5.5 times due to application of P fertilizers.