添加化学改良剂对海南岛砖红壤中铅的化学形态与转化的影响

Chemical Forms and Transformations of Pb in Granitic Latosol on Hainan Island Through Adding Chemical Amendments

采用土培试验和连续提取-原子吸收分光光度法,研究了海南岛花岗岩砖红壤中重金属Pb的6种形态(水溶态Pb、交换态Pb、碳酸盐结合态Pb、铁锰氧化物结合态Pb、有机质结合态Pb和残余态Pb)、外源Pb污染对土壤Pb形态的影响以及化学修复剂磷、钙、硫对土壤Pb形态的影响。结果表明,在供试原土壤中,重金属Pb的化学形态以结合态和残余态为主,土壤有效态Pb含量较低,其中:残余态Pb>有机质结合态Pb>铁锰氧化物结合态Pb>碳酸盐结合态Pb>交换态Pb>水溶态Pb,说明土壤Pb的环境风险较低。当外源Pb以离子态污染土壤时,土壤中6种形态Pb的含量均有明显上升,且随时间推移,外源Pb污染土壤中Pb的化学形态发生了连续变化,有:水溶态Pb和交换态Pb的比例持续下降,碳酸盐结合态Pb和铁锰氧化物结合态Pb的比例持续上升,有机质结合态Pb和残余态Pb的比例则有先升后略有下降再趋于稳定的趋势;土壤中Pb主要以铁锰氧化结合态累积,并有:铁锰结合态Pb>残余态Pb>有机态Pb>碳酸盐结合态Pb>交换态Pb>水溶态Pb的趋势。向污染土壤施加化学改良剂过磷酸钙、硫化钠和石灰,能显著降低水溶态Pb和交换态Pb的含量,可使有机结合态Pb、碳酸盐结合态Pb和铁锰氧化物结合态Pb含量下降,而残余态Pb有增加的趋势。化学改良剂的加入可使土壤Pb的有效态含量降低、活性下降,从而可抑制重金属Pb由土壤向植物体系的迁移,有利于植物安全生产。

The transformation processes of Pb in granitic latosol on Hainan island were characterized and the effect of exotic Pb and three soil amendments on its chemical forms in the soil studied. Results show that a major fraction of Pb in the original tested soils is in bond form and residual form and the content of available form is low, which indicates a low environmental risk. The percentage of Pb in different forms increased in the order：residual〉 organic〉Fe-Mn oxide〉 carbonate〉exchangeable〉water soluble form. The percentage of Pb in six forms in the soil increased significantly when exotic Pb enters soil in the ion form. As time goes, the chemical forms in the exotic Pb polluted soil change continuously as followed： （ 1 ）the percentage of water soluble form and exchangeable form decreased; （2）the percentage of carbonate and FeMn oxide forms increased;（3）the tendency of the percentage of residual, organic forms shaped as inverted＂U＂ ; （4）Fe-Mn oxide form was cumulated in the soil and the percentage of Pb in different, forms increased in the order：Fe-Mn oxide〉residual〉 organic〉 carbonate〉exchangeable〉water soluble form. The application of three soil amendments （calcium superphosphate, lime, sodium sulphide ）can significantly reduce the percentage of Pb in water soluble and exchangeable forms. The tendency indicates that soil amendents can reduce the percentage of Pb in effective forms and activity of Pb, which restrain the transfer of Pb from soil to plant and ensures the safety of plants.