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

Abstract

ABSTRACT 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(III)) 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(III) 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(III) versus As(Ⅴ) in nearby GW to ultimately impact the local ecological quality and human health.