3.4. Effects of Inorganic Nitrogenous Fertilizers on Arsenic Mobilization under Anaerobic Incubation.Unlike the phosphorus fertilizers, the addition of nitrogenous fertilizers with 500 mg/L ammonium sulfate under anaerobic conditions did not show a significant effect on the increase ofarsenic solubility in either sterilized or nonsterilized sediments (Figure 4). This suggests that nitrogenous fertilizers do not have a significant role in the release of arsenic into groundwater. It is interesting that one study reported that the application of nitrogen fertilizers increased the release of arsenic from sediment to groundwater in Bangladesh,51 which differs from our present finding. It is likely that there are different microorganisms present in the sediments in different regions (Bangladesh vs BFD region), resulting in different arsenicrelease mechanisms.