固定剂对土壤中Cr形态变化及生物可利用性的影响

为了考察固定剂对土壤中重金属Cr形态变化及生物可利用性的影响,用天然沸石、FeSO4、MgO质量比为2∶1∶1的物质组合作为固定剂,取一定量风干后的Cr污染棕壤土样,按照5%的比例加入固定剂。在封闭的体系里培养1周后,用Tessier序列提取法提取土壤中添加固定剂前后不同污染程度时各形态的Cr,并对生物可利用性进行评价。结果表明,Cr在土壤中的存在形态以残渣态比例最高,固定剂的添加使Cr向稳定的铁锰结合态和有机结合态方向转变,降低了碳酸盐结合态的比例,从而使Cr的生物利用性和迁移性降低,减小了Cr进入生物链的几率,一定程度保证了土壤使用的安全性。

Immobilization agent influence on the heavy metal Cr morphological transformation and bioavailability contained in the soil

The paper is aimed at presenting the results of our study of the effects of the immobilization agent on the heavy metal Cr morphological transformation and bioavailability of the soil.For our research objective,we have done experiments with the materials combined of natural zeolite,FeSO4 and MgO according to the quality ratio of 2:1:1 as the immobilization agent.Practically speaking,we have taken the dried brown soil polluted by Cr mixed with the immobilization agent in the ratio of 5% as the testing agent.The reason of the choice is that the soil is in favor of growing the local plants and the biological circulation of the nutritional elements are helpful for leaching and deposition for the brown soil forming process.After cultivating a week in the closed system in the local natural environment simulated conditions free from foreign material pollution,we picked up the soils polluted by different forms of chromium at different levels with immobilization agent in the Tessier sequential extraction process,and then make assessment of bioavailability and mobility of chromium by using atomic absorption spectrometry.The results show that,the residual of the soil has a high percentage of heavy metals Cr both in the soil with immobilization agent or in the soil without immobilization agent.Besides,the addition of immobilization agent tends to increase the proportion of the metal and makes part of exchangeable form and the carbonate combination form of Cr.We have also found that the addition of immobilization agent tends to increase the proportion and makes part of exchangeable form and carbonate combination form of Cr tend to stabilize the Fe-Mn oxide form and organic form so as to reduce the exchangeable form and the carbonate form in the heavier polluted soils,such as No.2 and No.3 soil samples.And,consequently,the bioavailability and mobility of chromium in the soil are reduced,which means that it is possible for the chromium in the soil to enter the biological chain with the groundwater being lower.Thus,it can be concluded that the addition of immobilization agent helps to improve the safety of the polluted soil.However,strict control should be made to the limited usage of immobilization agent so as to reduce pollution of the soil.