灌溉对非饱和带中砷迁移转化过程的影响

Influence of Irrigation Practices on Arsenic Mobilization and Transformation in the Unsaturated Zone

通过场地灌溉试验,探讨了灌溉活动对非饱和带中砷迁移转化过程的影响机理。结果表明:灌溉过程中非饱和带中砷的迁移转化受多个地球化学过程共同控制,非饱和带pH值、Ec值、SO_4^(2-)和HCO_3^-与As的竞争吸附以及氧化还原条件的波动都会影响土壤孔隙水中砷的质量浓度。灌溉活动导致土壤处于相对还原环境,铁氧化物矿物还原溶解,被吸附或与之共沉淀的砷被释放进入水相,灌溉结束后,土壤逐渐恢复相对氧化环境,重新生成铁氧化物矿物,土壤孔隙水中砷以吸附/共沉淀形式被其固定。因此,通过改变非饱和带氧化还原条件导致铁氧化物矿物的沉淀/溶解是灌溉作用下非饱和带水体中砷迁移转化的主要原因。

In this study,the influence mechanism of irrigation practices on arsenic mobilization and transformation in the unsaturated zone is discussed by field irrigation practices.The results show that arsenic mobilization in the unsaturated zone during high arsenic groundwater irrigation practices is influenced by multiple geochemical process.The arsenic concentration is affected by the pH,the competitive adsorption between SO4^2- and HCO3^- and the redox volatility in the unsaturated zone.During the irrigation,the soil is in the relatively reducing conditions,the iron oxide mineral is dissolved,and the arsenic which is combined with their on oxide mineral due to coprecipitation or sorption is released into soil pore water.After the irrigation,the soil comes into the relatively oxidizing conditions,in which the iron oxide mineral precipitates,and the arsenic of soil pore water is fixed by the iron oxide mineral due to coprecipitation or sorption.Therefore,the change of the redox condition,which causes the precipitation/dissolution of the iron oxide mineral,is the main reason of arsenic mobilization in the unsaturated zone in irrigation practices.