Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
Sci Total Environ. 2018 Jan 15;612:1463-1472. doi: 10.1016/j.scitotenv.2017.09.015. Epub 2017 Sep 25.
Remediation of CCA-contaminated soil (Cr, Cu, and As) by biodegradable chelant-enhanced washing (EDDS, S,S-ethylene-diamine-disuccinic-acid) needs further enhancement. This study investigated the effectiveness of coupling with pre-treatment by selective dissolution and post-treatment by soil amendments, respectively. Three groups of reagents (reductants, alkaline solvents, and organic ligands) were adopted in the pre-treatment to dissolve the oxide minerals before EDDS extraction. In the post-treatment, soil amendments (coal fly ash (CFA), acid mine drainage sludge (AMDS), green waste compost (GWC)), and their mixtures) were used for a 2-month stabilization after 2-h EDDS washing. Multi-endpoint evaluation was performed by assessing the chemical state, leachability, mobility, bioaccessibility, and plant-availability of residual metal(loid)s as well as the cytotoxicity, enzyme activities, and available nutrients of the treated soils. Pre-treatment by dithionite-citrate-bicarbonate significantly enhanced extraction efficiency, but also increased the leachability of As and Cr and bioaccessibility of Cr in the treated soils. While sodium hydroxide removed the majority of As without increasing its leachability and bioaccessibility, it increased the cytotoxicity and inhibited the acid phosphatase activity. Post-treatment with AMDS and CFA effectively controlled the mobility and leachability of residual As and Cr after EDDS washing. However, destabilized Cu was only marginally immobilized by GWC due to strong Cu-EDDS complexation. The bioaccessibility and phytoavailability of Cu was primarily reduced by EDDS washing, while those of As and Cr could be attenuated by AMDS and CFA. This study indicates that coupling chemical extraction with subsequent soil amendment plays complementary roles in mitigating effects of residual metal(loid)s and improving environmental quality.
用可生物降解的螯合剂增强洗涤（EDDS，S，S-乙二胺二琥珀酸）修复受 CCA 污染的土壤（Cr、Cu 和 As）需要进一步加强。本研究分别考察了与选择性溶解预处理和土壤改良剂后处理相结合的效果。在预处理中采用了三组试剂（还原剂、碱性溶剂和有机配体），以溶解 EDDS 提取前的氧化物矿物。在后处理中，采用土壤改良剂（粉煤灰（CFA）、酸性矿山排水污泥（AMDS）、绿色废物堆肥（GWC））及其混合物，在 2 小时 EDDS 洗涤后进行 2 个月的稳定化。通过评估残留金属（类）的化学状态、浸出性、迁移性、生物可利用性和植物有效性以及处理土壤的细胞毒性、酶活性和有效养分，对多终点进行了评价。二硫代柠檬酸盐-碳酸氢盐预处理显著提高了提取效率，但也增加了处理土壤中 As 和 Cr 的浸出率和生物可利用性。而氢氧化钠去除了大部分 As，但没有增加其浸出率和生物可利用性，反而增加了细胞毒性并抑制了酸性磷酸酶活性。AMDS 和 CFA 后处理有效地控制了 EDDS 洗涤后残留 As 和 Cr 的迁移性和浸出率。然而，由于强 Cu-EDDS 络合作用，GWC 对不稳定的 Cu 仅略有固定作用。Cu 的生物可利用性和植物有效性主要通过 EDDS 洗涤降低，而 As 和 Cr 的生物可利用性和植物有效性可通过 AMDS 和 CFA 降低。本研究表明，将化学提取与随后的土壤改良相结合，在减轻残留金属（类）的影响和改善环境质量方面具有互补作用。
