State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, PR China; College of Environment and Ecology, Chongqing University, Chongqing 400044, PR China.
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, PR China; Key Laboratory of Southwest Resources Exploitation and Environmental Hazards Controlling Engineering of Education Ministry, Chongqing University, Chongqing 400044, PR China; College of Environment and Ecology, Chongqing University, Chongqing 400044, PR China.
Sci Total Environ. 2021 Oct 10;790:148140. doi: 10.1016/j.scitotenv.2021.148140. Epub 2021 May 29.
In the remediation of Cr(VI)-contaminated soils, the effectiveness and long-term stability are critical qualities for the selection of a reductant. In current engineering practices, iron-based materials and sulfides are the most prevalent reductants, and calcium polysulfide (CaS) is considered as the one with the highest effectiveness and strongest long-term stabilization ability. But this opinion is questioned by the high interference ability of CaS to soil Cr(VI) analysis. This study provides a pretreatment method to eliminate the interference of residual ferrous and sulfides to soil Cr(VI) analysis. By this pretreatment method and comparing with FeSO and NaS, the mechanisms of the false high effectiveness and strong long-term stabilization ability of CaS is revealed. In the remediation process, CaS produces much elemental sulfur (S) which remains in the soils. During the alkaline digestion, the S generates polysulfide which reduces the extracted Cr(VI), inducing serious negative analysis bias. When this negative bias is eliminated by pretreatment method, analysis results show that CaS exhibits lowest effectiveness. The S cannot be leached away from soils and oxidized by oxygen under natural conditions, this makes CaS exhibit a persistent interference ability, which is mistaken for a strong long-term stabilization ability.
在六价铬污染土壤的修复中，还原剂的有效性和长期稳定性是选择的关键质量。在当前的工程实践中，铁基材料和硫化物是最常见的还原剂，而多硫化钙（CaS）被认为是效果最好、长期稳定性最强的还原剂。但这种观点受到 CaS 对土壤六价铬分析的高干扰能力的质疑。本研究提供了一种预处理方法，以消除残余亚铁和硫化物对土壤六价铬分析的干扰。通过这种预处理方法，并与 FeSO 和 NaS 进行比较，揭示了 CaS 具有高假有效性和强长期稳定能力的机制。在修复过程中，CaS 会产生大量元素硫（S），这些硫会留在土壤中。在碱性消解过程中，S 会生成多硫化物，从而减少提取的六价铬，导致严重的负分析偏差。当通过预处理方法消除这种负偏差时，分析结果表明 CaS 的效果最低。S 不能从土壤中浸出，也不能在自然条件下被氧气氧化，这使得 CaS 表现出持久的干扰能力，这被误认为是强的长期稳定性。
