Influences of Simulated Organic Residues in Petroleum-Exploiting Areas on the Dissolution and Speciation of Arsenic in Soil-Mineral Solid

Enhanced subsurface reductive potentials and anaerobic conditions induced by organic residues at oilfield sites may affect arsenic (As) levels in groundwater (GW) and GW-irrigated crops. To substantiate this effect, a Fe/Mn-As binary mineral oxide (FMBO-As) was synthesized by co-precipitation and a series of soil columns packed with varying FMBO-As levels were eluted with simulated oily wastewater to evaluate total As levels and As speciation. According to results from FTIR, XPS, SEM, and EDS analyses, As in synthesized FMBO-As particles exist in certain Fe-O-As bonding states. Both total As and arsenite (As(& x2162;)) fraction in soil-column leached solutions increased significantly with increasing FMBO-As packed in soil columns when leached by the simulated oily sewage water. Meanwhile, the total As and As(& x2162;) levels in leachate were well correlated with the leaching time, the chemical oxygen demand (COD), and the abundance of sulfate-reducing bacteria in simulated oily wastewater. Especially when the COD value was 51040 mg/L, the increase percentage of total As in the leachate has reached to 64.2%-186.6% at a leaching time of 2 to 18 days. These findings support the view that wastewaters from petroleum exploiting sites enhance the release of soil-and/or mineral-bound As and the distribution of As(& x2162;) versus As(& x2164;) in nearby GW to ultimately impact the local ecological quality and human health.