铁锰氧化物在不同水分条件下对土壤As的稳定化作用

本文以铁锰氧化物(Fe-Mn,FM)为研究对象,评估其在不同水分条件下对我国南方3种砷(As)污染土壤的稳定化修复效果.结果表明,添加一定比例(质量分数30%)水分对于抑制土壤As的毒性浸出具有积极作用,但水分过高(淹水条件)则会引发As的大量活化释放.淹水条件下,FM对As污染土壤具有明显的应用优势,能使韶关、河池和常德这3种土壤毒性浸出质量浓度均显著下降99. 00%以上,使其土壤有效态As含量分别显著降低55. 40%、40. 05%和16. 92%,并增加专性和非专性吸附态As向水合铁铝氧化物结合态的稳定化. FM能使韶关、河池和常德土壤有效态磷(P)含量分别降低0. 60%～6. 67%、15. 74%～50. 00%和32. 48%～40. 39%,这有可能会限制缺P区域农产品对酸性或中性土壤的P摄取. FM对3种供试土壤p H值影响的变化幅度仅为0. 04～0. 07,对土壤环境的影响非常小. FM在我国淹水As污染土壤稳定化修复领域具有较好的应用前景.

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.