相对湿度对铁锰氧化物表面甲基对硫磷降解行为的影响OA

The pollution of soil by organophosphorus pesticides(OPPs)has attracted widespread attention from researchers.Exploring the environmental behaviors of OPPs on the surface of soil iron-manganese oxides is crucial for clarifying the environmental fate of such pollutants.The degradation behaviors of methyl parathion(MP)by seven iron and manganese oxides with different crystal forms were investigated under limited moisture conditions.Results showed that MP mainly underwent hydrolysis on the surface of iron oxides and iron-manganese oxides,while both hydrolysis and oxidation reactions occurred simultaneously on the surface of manganese oxides.When the relative humidity(RH)was in the range of 33%-76%,the hydrolysis rate of MP by iron oxides reached the maximum(1.37×10-2 h-1).For manganese oxides,there was a significant negative correlation between the observed degradation rate(Kobs)of MP and RH.As RH increased from 5%to 100%,the Kobs value decreased from 0.66 h-1 to 0.31 h-1.In addition,the degradation rate of MP by α-MnO2(0.276 h-1·m-2)was 2～3 orders of magnitude higher than that of goethite(0.010 6 h-1·m-2)and iron-manganese oxides(0.004 03 h-1·m-2).The hydrolysis of MP by iron oxides and manganese oxides was jointly controlled by surface hydroxyl groups and Lewis acid sites,while the hydrolysis by the iron-manganese oxide was governed exclusively by the surface Lewis acid sites.The findings of this study underscore the impact of limited moisture conditions on the catalytic transformation of OPPs by iron and manganese oxides,and also reveal the likely long-overlooked abiotic transformation behavior of such pollutants in the soil environment.