This paper focuses on the abiotic reduction of selenite (Se(IV)) by cysteine (Cys, NH3+CH(CH2SH)COOH), which is a representative thiol produced by aquatic organism under oxidative stress. The rates of reduction of Se(IV) by cysteine were measured in deaerated NaCl solutions and natural waters as a function of pH (4.0-9.0), temperature (10-40C), and ionic strength (0.01-1.0M). The rates showed a complex dependence on pH with similar values from pH 4.0-5.0, increasing values from pH 5.0-7.0 and then decreasing values at pH higher than 7.0. An apparent energy of activation obtained was 316kJmol-1, which was independent of ionic strength. 2013 Elsevier Ltd.
