Controlled variation of redox conditions in a floodplain soil: impact on metal mobilization and biomethylation of arsenic and antimony.

摘要

An automated biogeochemical microcosm system allowing the control of redox potential (E_H) in soil suspensions was used to assess the effect of E_H on the mobility of cadmium (Cd), copper (Cu), nickel (Ni), zinc (Zn), iron (Fe), and manganese (Mn) as well as on the methylation of arsenic (As) and antimony (Sb) in a contaminated and slightly acidic floodplain soil. The experiment was conducted under stepwise variation from reducing (approximately -300 mV at pH 5) to oxidizing (+600 mV at pH 5) conditions. The E_H was found to be an important factor controlling the dynamics of studied compounds and elements. Concentrations of Cd, Cu, Mn, Ni, and Zn in solution were low at low E_H and increased with rising E_H what might be attributed to the interaction with dissolved organic carbon (DOC), Mn, and precipitation as sulphides. Redox potential and pH correlate significantly with Cd, Ni, Cu, Zn, and Mn. Total Fe concentrations in solution were high at low E_H and dropped sharply at E_Hi) and antimony (Sb_i), momomethyl arsenic (MMAs), monomethyl antimony (MMSb), and dimethyl arsenic (DMAs) in solution decreased significantly with rising E_H, indicating that low E_H promotes the mobility of these compounds.