Reclamation of arsenic contaminated soils around mining site using solidification/stabilization combined with revegetation

Abstract

Arsenic (As) is a known carcinogen and is one of the most commonly reported contaminants in farmland soils around mining sites. This study aimed to investigate four different soil amendments (rice husk biochar (RHB), maple leaf biochar (MLB), red mud (R.M), and steel slag (S.S)) with respect to the stabilization of arsenic in soil combined with revegetation of two hyperaccumulators (Asteraceae (lettuce) and Brassicaceae (mustard green)). Soil amendments at different application rates (0.5%, 1%, and 2% w/w) and small particle sizes (<74 μm) were added to the soil. A different pattern was observed for stabilization of As in treated soils. A meaningful decline in As stabilization was observed with increasing application dosage of MLB, R.M, and S.S, while in case of RHB efficiency was increased. Generally, maximum stabilization efficiency of As was observed following the adding of RHB (2%), MLB (0.5%), R.M (0.5%), and S.S (0.5%), by 90%, 94%, 94%, and 89%, respectively, which was primarily attributed to amendments-induced specific surface area within the structure. For lettuce, As was strongly accumulated by leaves, while As, for mustard green, was extracted much more by its roots. Sequential extraction analysis confirmed high proportions of Fe and Mn oxides and organic fractions of As, before and after planting. Altogether, the establishment of a suitable plant cover on treated soil with amendments showed encouraging results for preventing the dispersion of As through runoff and percolation. Besides, this combined technique, which is aesthetically pleasant, increases biodiversity.