基于中性盐提取的土壤重金属固液分配与自由态金属离子浓度测定

Solid-solution partitioning of soil heavy metals and free-ion concentration measurement in neutral salt extractions

采用0.01mol·L-1CaCl2、0.002mol·L-1Ca(NO3)2和纯水(UPW)3种常用提取剂对我国南方两种典型农田重金属污染土壤进行提取试验.同时,应用土壤重金属固液分配多表面模型来预测提取液中重金属含量,结合道南膜技术(DMT)测定Ca(NO3)2提取液中自由态金属离子浓度,并与ECOSAT模型计算值进行比较.结果表明,提取剂中Ca2+浓度增加能显著提高土壤重金属溶出率,而提取液pH、溶解态有机碳(DOC)浓度却随溶液Ca2+浓度增加而降低.多表面模型(Multi-Surface Model)对大部分提取液金属浓度有较好的预测效果,部分土样提取液Cu、Pb、Zn浓度的预测效果较差.DMT测定的Ca(NO3)2提取液自由态重金属浓度与模型计算值较为一致,能够较准确地测定土壤溶液自由态重金属离子浓度.

To investigate the solid-solution partitioning of soil heavy metals, two typical agricultural soils were collected from Southeast China, and heavy metal extraction experiments were carried out using 0.01 mol·L^-1 CaCl2, 0.002 mol·L^-1 Ca（NO3）2 and Ultra Pure Water（UPW）. The heavy metal concentrations in the extracts were calculated by a Multiple Surface Model （MSM） which could describe the speciation and partitioning of heavy metals in soils. The free ion concentrations were measured by the Donnan Membrane Technique （DMT） and compared with the ECOSAT model predicted values. The results showed that heavy metal concentrations in solution increased with increasing Ca^2＋ concentration, but solution pH and DOC concentrations decreased with the increase of Ca^2＋ in the solution. The Multiple Surface Model could give quite good predictions except for Cu, Zn and Pb values of some soil samples. The free ion concentrations measured by DMT were consistent with the values predicted by the model.