Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW, 2308, Australia; Department of Soil Science, Sher-e-Bangla Agricultural University, Dhaka, 1207, Bangladesh.
Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, Victoria, 3000, Australia.
Chemosphere. 2022 Jun;296:134053. doi: 10.1016/j.chemosphere.2022.134053. Epub 2022 Feb 18.
Arsenic contamination in abandoned soils is a global concern which warrants an effective method of remediation. In this study, two organic acids and one biodegradable chelating agent were used to treat arsenic (As) contaminated abandoned mine soils. The concentration of As was 19,100 and 75,350 (mg/kg) for Webbs Consols (WC) and Mole River (MR) samples, respectively. X-ray diffraction and scanning electron microscopy confirmed that tooeleite, arsenopyrite, scorodite and quartz were the major minerals in these soils. A major portion of the As was composed of amorphous and crystalline oxides of Fe and Al determined by sequential extraction. Among the three washing reagents (oxalic acid, citric acid and EDDS) oxalic acid showed the best performance for extracting As. Based on the batch experiment, 0.5 M oxalic acid and 3 h of washing was the most efficient treatment to extract As and other trace elements. Extraction of As, Fe, and Pb was 70, 55, and 48% respectively for WC, while 68, 45 and 63% respectively for MR soil. Oxalic acid extracted 75 and 83% of As and Fe, respectively from tooeleite. Leachability and bioaccessibility of As and Fe in the treated soil was reduced due to washing. However, bioaccessibility and leachability of Pb in soil and Fe and As in tooeleite increased in washed samples. Though the leachability and bioaccessibility of As and Fe in soil was reduced in the treated soil, As still exceeded the USEPA criteria (5 mg/L) which is needed to successfully remediate soil by washing. Soil washing and subsequent solidification/stabilization could be an alternative option to remediate extremely contaminated abandoned mine soil.
废弃土壤中的砷污染是一个全球性问题，需要采用有效的修复方法。本研究采用两种有机酸和一种可生物降解的螯合剂处理砷（As）污染的废弃矿山土壤。Webbs Consols（WC）和 Mole River（MR）土壤样品中砷的浓度分别为 19100 和 75350（mg/kg）。X 射线衍射和扫描电子显微镜证实，太傲石、毒砂、砷铁矿和石英是这些土壤中的主要矿物。顺序提取法确定，大部分砷由铁和铝的无定形和结晶氧化物组成。在三种洗涤试剂（草酸、柠檬酸和 EDDS）中，草酸对提取砷的效果最好。基于批量实验，0.5 M 草酸和 3 小时的洗涤是提取砷和其他微量元素最有效的处理方法。WC 土壤中，As、Fe 和 Pb 的提取率分别为 70%、55%和 48%；MR 土壤中，As、Fe 和 Pb 的提取率分别为 68%、45%和 63%。草酸从太傲石中分别提取了 75%和 83%的砷和铁。洗涤后，处理土壤中砷和铁的浸出率和生物可利用性降低。然而，在洗涤后的样品中，土壤中 Pb、太傲石中 Fe 和 As 的生物可利用性和浸出率增加。尽管处理土壤中砷和铁的浸出率和生物可利用性降低，但仍超过美国环保署（USEPA）的标准（5 mg/L），需要通过洗涤来成功修复土壤。土壤洗涤和随后的固化/稳定化可能是修复极度污染的废弃矿山土壤的替代选择。
