Abstract
The goal of this study was to quantify the mobility and partitioning of trace elements originating from mine waste rocks derived from open pit coal extraction activities. The results showed that native rice plants were adapted to growing in metal contaminated soils, posing a severe health risk to local population. Sequential extraction procedures and bulk soil chemical analyses both suggest enrichment of Cd, Pb and Cu in rice paddy soils. Lead was shown to be evenly partitioned among all mineral and organic phases. Copper was associated with carbonates and organic matter. Smaller fractions of Pb and Cu were also bound to Fe and Mn oxides. Only 25% of Cd, 9% of Pb and 48% of Cu were associated with the exchangeable fraction, considered mobile and thus bioavailable for plant uptake. Effects of Cd, Cu and Pb on local Cam Pha Nep cai Hoa vang, and control Asia Italian rice, showed marked differences in growth. The local Vietnamese variety grew close to control values, even upon exposure to higher trace metal concentrations. Whereas the development of the control rice species was significantly affected by increasing trace metal concentrations. This result suggests toxic trace elements accumulation in the edible parts of crops.
Highlights
Open-pit coal mining in countries such as China and Vietnam, is one of the major causes of freshwater, soil and air pollution [1,2]
Sequential extraction of mine waste tailings from the Cam Pha area show a heterogeneous distribution of trace elements bound to distinct mineral composites (e.g., Pb to Fe-Mn oxides) and organic matter (e.g., Cu)
Chemical weathering of waste rocks, especially under tropical climate conditions, leads to an enhanced release of potentially toxic trace elements, which become mobile in agricultural soils and become bioavailable to essential food crops, such as rice
Summary
Open-pit coal mining in countries such as China and Vietnam, is one of the major causes of freshwater, soil and air pollution [1,2]. Waste rock material derived from open pit coal mining contains significant concentrations of reduced sulfides. These include pyrite (FeS2), chalcopyrite (CuFeS2) and other metal sulfides, including covellite (CuS), chalcocite (Cu2S) and galena (PbS). The chemical weathering of these minerals enhances the solubility, mobilization and bioavailability of trace metals [11]. In contaminated areas, these elements may be transported by colloidal or suspended particulates present in water used to irrigate agricultural land [12]
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