Fig. 4. Changes in the concentration of Se species, pH, and redox potential (Eh) of drainage water during 14 d of incubation with nonsterile rice straw. Selenium concentrations are given for the rice straw solution with the exception of total Se(0), which was determined as the difference between added Se(VI) and total soluble Se in the entire water and rice-straw system. Symbols , , and • show triplicate experiments. Batch 3 experiments.