LONG-TERM stability of arsenic in iron amended contaminated soil

This study aimed at elucidating the long-term efficiency of soil remediation where chemical stabilization of arsenic (As) contaminated soil using zerovalent iron (Fe) amendments was applied. A combination of chemical extraction and extended X-Ray absorption fine structure (EXAFS) spectroscopy technique was applied on soils collected from five laboratory and field experiments in Sweden and France. All soils were treated with 1 wt% of zerovalent Fe grit 2-15 years prior to the sampling. The results indicate that all studied soils, despite the elapsed time since their amendment with Fe grit, had substantial amounts of ferrihydrite and/or lepidocrocite. These metastable and the most reactive Fe (oxyhydr)oxides (mainly ferrihydrite) were still present in substantial amounts even in the soil that was treated 15 years prior to the sampling and contributed most to the As immobilisation in the amended soils. This increases confidence in the long-term efficiency of As immobilisation using zerovalent Fe amendments. Both applied methods, sequential extraction and EXAFS, were in line for most of the samples in terms of their ability to highlight As immobilisation by poorly crystalline Fe phases. (C) 2020 The Authors. Published by Elsevier Ltd.

Automated summary

This study investigated the long-term efficiency of soil remediation using zerovalent iron to stabilize arsenic contaminated soil. The results showed that even after 15 years, substantial amounts of ferrihydrite and lepidocrocite were still present in the soils, contributing to arsenic immobilization. Both sequential extraction and EXAFS techniques were effective in highlighting arsenic immobilization by poorly crystalline iron phases.