title: Integrating EDDS-enhanced washing with low-cost stabilization of metal-contaminated soil from an e-waste recycling site.
abstract: While chelant-enhanced soil washing has been widely studied for metal extraction from contaminated soils, there are concerns about destabilization and leaching of residual metals after remediation. This study integrated 2-h soil washing enhanced by biodegradable ethylenediaminedisuccinic acid (EDDS) and 2-month stabilization using agricultural waste product (soybean stover biochar pyrolyzed at 300 and 700 °C), industrial by-product (coal fly ash (CFA)), and their mixture. After integration with 2-month stabilization, the leachability and mobility of residual metals (Cu, Zn, and Pb) in the field-contaminated soil were significantly reduced, especially for Cu, in comparison with 2-h EDDS washing alone. This suggested that the metals destabilized by EDDS-washing could be immobilized by subsequent stabilization with biochar and CFA. Moreover, when the remediation performance was evaluated for phytoavailability and bioaccessibility, prior EDDS washing helped to achieve a greater reduction in the bioavailable fraction of metals than sole stabilization treatment. This was probably because the weakly-bound metals were first removed by EDDS washing before stabilization. Both individual and combined applications of biochar and CFA showed comparable effectiveness regardless of the difference in material properties, possibly due to the high level of amendments (150 ton ha(-1)). Based on the mobility and bioaccessibility results, the estimated human health risk (primarily resulting from Pb) could be mitigated to an acceptable level in water consumption pathway or reduced by half in soil ingestion pathway. These results suggest that an integration of EDDS washing with soil stabilization can alleviate post-remediation impacts of residual metals in the treated soil.
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Jingzi
authors.initials: J
authors.lastname: Beiyuan
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China. Electronic address: dan.tsang@polyu.edu.hk.
authors.forename: Daniel C W
authors.initials: DCW
authors.lastname: Tsang
authors.affiliation: School of Natural Resources and Environmental Science, Korea Biochar Research Center, Kangwon National University, Chuncheon 24341, Republic of Korea. Electronic address: soilok@kangwon.ac.kr.
authors.forename: Yong Sik
authors.initials: YS
authors.lastname: Ok
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Environmental Engineering, Chonbuk National University, Jeollabuk-do 561-756, Republic of Korea.
authors.forename: Kitae
authors.initials: K
authors.lastname: Baek
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Li
mesh_terms: D001673:Biodegradation, Environmental; D002606:Charcoal / Q000737:chemistry; D059029:Electronic Waste / Q000032:analysis*; D005029:Ethylenediamines / Q000737:chemistry*; D006801:Humans; D019216:Metals, Heavy / Q000737:chemistry*; D059027:Recycling; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D013386:Succinates / Q000737:chemistry*
chemical_list: D005029:Ethylenediamines; D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D013386:Succinates; C540010:biochar; D002606:Charcoal; C041447:N,N'-ethylenediamine disuccinic acid
keywords: Charcoal; Chelating agents; Heavy metals; Integrated remediation; Soil amendment