TY - JOUR
T1 - Chelant-enhanced washing of CCA-contaminated soil
T2 - Coupled with selective dissolution or soil stabilization
AU - Beiyuan, Jingzi
AU - Lau, Abbe Y.T.
AU - Tsang, Daniel C.W.
AU - Zhang, Weihua
AU - Kao, Chih Ming
AU - Baek, Kitae
AU - Ok, Yong Sik
AU - Li, Xiang Dong
N1 - Funding Information:
The authors appreciate the financial support from the Hong Kong Research Grants Council (PolyU 15222115 and 15223517 ) for this study.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/1/15
Y1 - 2018/1/15
N2 - 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.
AB - 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.
KW - Arsenic
KW - Biodegradable chelant
KW - Chromium
KW - Fly ash
KW - Soil amendment
KW - Soil washing
UR - http://www.scopus.com/inward/record.url?scp=85028979569&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2017.09.015
DO - 10.1016/j.scitotenv.2017.09.015
M3 - Article
C2 - 28903175
AN - SCOPUS:85028979569
SN - 0048-9697
VL - 612
SP - 1463
EP - 1472
JO - Science of the Total Environment
JF - Science of the Total Environment
ER -