Stability of Copper,Zinc and Phosphorus Accumulated in Sandy Agricultural Soils

Water quality impacted by heavy metals and nutrients accumulated in soils is a major environmental concern.Understanding the stability of the heavy metals and nutrients in the soils under different conditions is necessary to predict their potential impacts on water quality.In this study,the stability of Cu,Zn and P accumulated in sandy soils was examined by simulative leaching with deionized water,0.01 mol·L~(-1) CaCl_2,0.01 mol·L~(-1) HNO_3,and 0.01 mol·L~(-1) Na-EDTA.The chemical forms of Cu,Zn and P in the soils were also examined using a sequential fractionation method.The results indicated that most of Cu,Zn and P accumulated in the sandy soils were extractable fractions with high activity.pH had a great influence on solubility of Cu,Zn and P in the soils.Sensitivity to acidification of the solubility of the three elements decreased in the order of PZnCu.The concentrations of Cu,Zn and P in leachates varied greatly with leaching agents.The amounts of Cu,Zn,and P leached from the soils were Na-EDTA 0.01 mol·L~(-1) HNO_3 0.01 mol·L~(-1) CaCl_2 and deionized water,and related with chemical forms of Cu,Zn and P in the soils.The results suggested that Cu and Zn in the soils were more stable as compared with P under the current land use with high soil pH.However,soil acidification or/and increased soil soluble organic matter induced by afforestation may increase the release of Cu,Zn and P from the soils.