State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, PR China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, PR China.
J Hazard Mater. 2017 Jan 5;321:228-237. doi: 10.1016/j.jhazmat.2016.09.021. Epub 2016 Sep 9.
Although reductive dissolution of Fe(III) oxides has been well accepted for As mobilization in alluvial aquifers, the key factors controlling this process are poorly understood. Arsenic(V)-adsorbing ferrihydrite, goethite and hematite were used to examine in-situ mobilization and transformation of adsorbed As(V) and Fe(III) oxides. In the Hetao basin, seven wells with wide ranges of groundwater As were selected to host As(V)-Fe(III) oxides sand. During 80 d experiments, As was firstly desorbed and then released via reductive dissolution of iron oxide from ferrihydrite, while only desorption was observed from goethite/hematite sand. Desorbed As was predominantly controlled by groundwater HCO and DOC, while reductive dissolution-related As release was mainly regulated by ORP values, DOC and Fe(II) concentrations. Mineral transformation from ferrihydrite to lepidocrocite and goethite/or mackinawite would also contribute to As release. Arsenic species was transformed from As(V) to As(III) on ferrihydrite, but remained unchanged on goethite and hematite. Arsenic partition between As-Fe(III) oxide sand and real groundwater ranged between 0.012 and 0.102L/g. K between As-goethite sand/As-hematite sand and groundwater fell within the ranges observed between sediments and groundwater. This study suggests that As desorption, reductive dissolution and mineral transformation of ferrihydrite would be the major processes controlling As mobility.
尽管铁氧化物的还原溶解已被广泛接受为所有含砷含水层中砷的迁移机制，但控制这一过程的关键因素仍了解甚少。本研究采用砷（V）吸附的水铁矿、针铁矿和赤铁矿来考察吸附砷（V）和铁（III）氧化物的原位迁移和转化。在河套盆地，选择了 7 口具有广泛地下水砷浓度的井来容纳砷（V）-铁（III）氧化物砂。在 80d 的实验中，砷首先通过铁氧化物的还原溶解从水铁矿中解吸并随后释放，而仅从针铁矿/赤铁矿砂中观察到解吸。解吸的砷主要受地下水 HCO 和 DOC 控制，而与还原溶解相关的砷释放主要受 ORP 值、DOC 和 Fe(II)浓度调节。从水铁矿向纤铁矿和针铁矿/磁黄铁矿的矿物转化也会导致砷释放。砷物种在水铁矿上从砷（V）转化为砷（III），但在针铁矿和赤铁矿上保持不变。砷-铁（III）氧化物砂与实际地下水之间的砷分配系数介于 0.012 和 0.102L/g 之间。砷-针铁矿砂/砷-赤铁矿砂与地下水之间的 K 值在沉积物与地下水之间的观测范围内。本研究表明，水铁矿的砷解吸、还原溶解和矿物转化将是控制砷迁移的主要过程。
