铬污染土壤稳定化处理对蚯蚓的毒性效应

浸出毒性测试是评价重金属污染土壤稳定化处理效果的主要方法,但该方法不能准确反映稳定化处理后土壤的生物毒性变化.本研究以多硫化钙(CPS)稳定化处理的电镀厂铬(Cr)污染土壤为对象,以赤子爱胜蚓为指示生物,研究评估土壤稳定化处理的生物毒性效应.结果表明,在Cr污染土壤中,随着CPS投加量的增加,蚯蚓的毒性效应逐渐减弱随后增强.高浓度Cr污染土壤经过CPS稳定化处理后仍然具有明显的生物毒性,CPS与土壤中Cr(VI)投加比(物质的量比,下同)为3时土壤浸出毒性虽满足浸出标准,但对蚯蚓的7 d致死效应高达100%,且暴毒期间出现肉眼可见的外部形态变化,回避率为83.3%,在暴毒第5 d时蚯蚓体内总Cr含量为20.9 mg·kg~(-1).CPS对蚯蚓具有较强的生物毒性作用,在不含Cr污染的对照组土壤中,CPS投加量与稳定化处理Cr污染土壤中稳定化药剂投加比为5相同时,蚯蚓的7 d急性毒性致死率为100%.蚯蚓的致死率和外部形态变化可快速直观地反映重金属污染土壤的生物毒性,可为土壤稳定化处理的安全性与生物毒性评估提供参考依据.

The biotoxicity effect on earthworms by stabilization treatment of Cr-contaminated soil

Leaching toxicity test is an appropriate method to evaluate the stabilization treatment of heavy metal contaminated soil, but it cannot precisely reflect the biotoxicity changes after stabilization in soil. The objective of current study is to evaluate the biotoxicity effect of soil stabilization, Cr contaminated soil treated by CPS was selected as the research object, and Eisenia fetida was employed as indicator. According to obtained results the increase of CPS dosage in Cr contaminated soil lead to weakened toxicity effect on earthworms at first and was later strengthened. High concentration Cr contaminated soil showed obvious biotoxicity even after CPS stabilization, when molar ration of CPS to Cr(VI) was 3, the leaching toxicity could reach the leaching standard, but at the same ratio, earthworm mortality was up to 100% at the 7th day of exposure period with appearance of visible external morphological changes, while the avoidance rate was 83.3%, and the total Cr content of earthworms was 20.9 mg·kg^-1 at the 5th day of the exposure period. Moreover, CPS itself also possessed toxic effects on earthworms. In the control group soil, which contained CPS at the molar ration of 5 but no Cr contamination, the acute toxicity fatality of earthworms reached 100% at the 7th day of the exposure period. The fatality rate and morphological changes of earthworm directly showed the biotoxicity of heavy metal contaminated soils, that can be the reference to safety and biotoxicity evaluation of soil stabilization.