磷肥钝化修复重金属污染土壤及其环境风险

Immobilization remediation of heavy metal contaminated soil by phosphate fertilizer and its environmental risk

磷肥广泛应用于农田重金属污染土壤钝化修复,但不同类型磷肥对多种重金属复合污染土壤的修复效果及其环境风险尚不明确。通过室内土壤培养和土柱淋溶模拟实验,研究枸溶性磷肥-钙镁磷肥(CMP)和水溶性磷肥-磷酸二氢钾(MPP)对重金属Pb、Cd、Cu、Zn复合污染土壤的钝化效果以及磷在土壤剖面中的淋溶损失特征。结果表明,CMP和MPP施用量(以P_(2)O_(5)计)为8 g·kg^(-1)时,Pb、Cd的钝化率分别为35.05%和71.72%、31.76%和40.99%,而Cu、Zn则出现一定程度的活化(最高达29.62%)。MPP对Pb的钝化效果显著优于CMP,但对Cd而言,2者差异不明显,且磷肥用量的成倍增加并不能显著提升钝化效果。土柱中土壤全磷、有效磷和淋溶液总磷的质量分数均随着深度(20~65 cm)递增而显著下降,且在某一深度上随着施磷量(1~8 g·kg^(-1))的增加而显著升高。MPP在高用量下造成的磷淋溶风险显著大于CMP。采用磷肥钝化修复复合重金属污染土壤应综合重金属类型、钝化效果以及潜在的磷流失风险,选择适当的磷肥种类和用量。本研究结果可为磷肥钝化修复重金属污染土壤提供参考。

Phosphate fertilizer is widely used in the passivation remediation of heavy metal contaminated soils in farmland.However,the remediation effect and environmental risk of different types of phosphate fertilizer on soil contaminated by multiple heavy metals have not been fully concerned.By indoor soil culture and soil column leaching simulation experiments,the passivation effect of calcium-magnesia phosphate(CMP)(citric soluble)and monopotassium phosphate(MPP)(water soluble)on Pb,Cd,Cu,Zn contaminated soil and the characteristics of phosphorus leaching loss in soil profile were investigated.The results showed that when the application rate of CMP and MPP(measured by P_(2)O_(5))was 8 g·kg^(-1),the passivation rates of Pb,Cd were 35.05%and 71.72%,31.76%and 40.99%,respectively,while Cu and Zn were activated to a certain extent(up to 29.62%).The passivation effect of MPP on Pb was obvious better than that of CMP,but for Cd,the difference was not obvious,and the doubling of the amount of phosphate fertilizer did not obvious improve the passivation effect.The mass fraction of soil total P,available P and total P in leaching solution in the soil column decreased significantly with the increase of depth(20~65 cm),and at a certain depth,with the application of phosphorus(1~8 g·kg^(-1))increased significantly.The risk of phosphorus leaching caused by MPP at high application rate was obvious higher than that caused by CMP.When using phosphate fertilizer passivation to remediate multiple heavy metal contaminated soil,the types of heavy metals,the passivation effect and the potential risk of phosphorus loss should be synthetically considered,and the appropriate type and amount of phosphate fertilizer should be selected.The results of this study can provide a reference for the remediation of heavy metal contaminated soil by phosphate fertilizer passivation.