[Stabilization of Arsenic-Contaminated Soils Using Fe-Mn Oxide Under Different Water Conditions]

Fe-Mn oxide (FM) was used to evaluate its stabilization effects on three typical arsenic (As)-contaminated soils in southern China under different water conditions (dry soil, moist soil, and flooded soil). With an increase in moisture content, the toxicity characteristic leaching procedure (TCLP) results for As decreased by 34.78%, 47.62%, and 13.64%, respectively,in Shaoguan,Hechi, and Changde, and then increased by 310.34%, 185.22%, and 23.38%, respectively. The results showed that adding a certain amount of water (30%) had a positive effect on decreasing the As concentration in the TCLP, but excessive amounts (80%) led to As re-release into the soil. The application of FM under flooding conditions has obvious advantages. In the three soils of Shaoguan,Hechi, and Changde, FM significantly reduced the As concentration in the TCLP by more than 99.00%, and reduced the soil available As content by 55.40%, 40.05%, and 16.92%, respectively. FM increased the specificandnon-specific adsorption of As to stabilize the bound fractions of hydrated iron-aluminum oxide, thus significantly reducing the biological effectiveness of soil As and soil environmental risk.FM reduced the available P in the soil in Shaoguan,Hechi, and Changde by 0.60%-6.67%, 15.74%-50.00%, and 32.48-40.39%, respectively. Our study revealed that FM can absorb a small amount of available P, which may limit P uptakeby agricultural products in P-deficient areas, while effectively inhibiting the non-point source pollution of soil to surrounding water bodiesin P-rich areas. The variation in pH after FM application in the three soils was only 0.04-0.07, which had little effect on the soil environment. FM has good prospects for stabilization of flooded As-contaminated soil. The results of this study provide an important scientific basis for soil As stabilization in China.