The reduction of Se(IV) with ascorbic acid: it's relevance in aqueous and soil solutions

Abiotic processes able to reduce oxidized Se species may have a strong influence on the environmental behavior of selenium since Se toxicity, bioavailability and mobility followthe order Se(-II) < Se(0) < Se(IV) < Se(VI). Ascorbic acid, which is exudated from plant roots, aquatic macrophytes and phytoplankton and also derives fromdecomposition of organic matter (e.g. litter, dead roots, algal cells), is present either in soil solution or in the water phase and may interact with Se affecting its speciation and environmental behavior. The rates of the reduction of Se(IV) by ascorbic acid (C6H8O6 = H2A) were measured in NaCl and NaClO4 solutions with 1 lM Se(IV) and 100–1000 lM H2A as a function of pH, temperature and ionic strength and in the presence of possible interfering metals.