“…In addition to hydrothermal deposits, arsenic may readily interact with sulfide in anoxic sediments, soils, and waters at temperatures <50 • C (Figure 3.3). In these highly reducing environments, arsenic may precipitate as sulfide compounds, form thioarsenic species, adsorb onto Fe(II) sulfides, and/or possibly coprecipitate with Fe(II) sulfides (Chaillou et al, 2003), 3001; (Reisinger, Burris and Hering, 2005), 459A, 461A; (Nicholas et al, 2003); (Jay et al, 2005). In a low-iron and sulfide-rich reducing environment, the absence of Fe(II) sulfide precipitation could cause H 2 S concentrations to dramatically increase.…”