In contrast, reduced Fe(II) and As(III) are practically the sole species in the more reducing landfill environment. Relatively high solubility of Fe(II) and low sorption affinity of As(III) would always render the iron-laden sludge more susceptible to rapid leaching under the oxygen-starved environment of the landfill or underground waste site.In an aerated (i.e.,oxidizing) environment arsenic and iron leaching are minimized.