Gamble Audrey V, Givens Alyssa K, Sparks Donald L
J Environ Qual. 2018 Jan;47(1):121-128. doi: 10.2134/jeq2017.07.0264.
Lead arsenate is an environmentally hazardous contaminant that was applied as a pesticide in orchards during the early 1900s. Elevated arsenic (As) concentrations persist in soils where lead arsenate was applied. To assess the risk associated with historic lead arsenate contamination, the retention, bioavailability, and speciation of soil As were evaluated in three historically contaminated orchard soils. Stirred-flow desorption studies and in vitro physiologically based extractions were used to assess the mobility and relative bioavailability of soil As, respectively. Synchrotron-based X-ray absorption spectroscopy was used to determine soil As speciation. Arsenic concentrations in former orchard soils ranged from 11.8 to 59.0 mg kg. Less than 22% of total As was considered bioavailable according to in vitro extractions. Up to 15% of soil As was desorbed in 10 mM KCl, but desorption with phosphate solutions resulted in release of up to 70% of total As dependent on soil type. Desorption data suggest that arsenate is primarily sorbed via inner-sphere complexation, and elevated concentrations of competing ions in soil solution may increase mobility of soil As. Arsenic was primarily present in the As(V) oxidation state, the less mobile form of As. Combined results from X-ray absorption spectroscopy and desorption studies indicate that As primarily exists as sorbed species, likely to ubiquitously present Fe- and Al-oxides in soils. Results demonstrate that soil As from these historically contaminated orchards is mostly in stable, nonhazardous forms, but factors such as Fe- and Al-oxide content and land management practices have a significant effect on As transport and bioavailability.
砷酸铅是一种对环境有害的污染物，在20世纪初曾被用作果园杀虫剂。在曾施用砷酸铅的土壤中，砷（As）浓度仍然很高。为评估与历史上砷酸铅污染相关的风险，对三个历史污染果园土壤中砷的保留、生物有效性和形态进行了评估。分别使用搅拌流解吸研究和体外生理基础提取法来评估土壤中砷的迁移率和相对生物有效性。使用基于同步加速器的X射线吸收光谱法来确定土壤中砷的形态。前果园土壤中的砷浓度范围为11.8至59.0 mg/kg。根据体外提取法，总砷中不到22%被认为具有生物有效性。高达15%的土壤砷在10 mM KCl中被解吸，但用磷酸盐溶液解吸时，根据土壤类型，总砷的释放量高达70%。解吸数据表明，砷酸盐主要通过内球络合作用吸附，土壤溶液中竞争离子浓度的升高可能会增加土壤中砷的迁移率。砷主要以As(V)氧化态存在，这是砷的迁移性较低的形式。X射线吸收光谱法和解吸研究的综合结果表明，砷主要以吸附态存在，可能是土壤中普遍存在的铁和铝氧化物。结果表明，这些历史污染果园土壤中的砷大多以稳定、无害的形式存在，但铁和铝氧化物含量以及土地管理实践等因素对砷的迁移和生物有效性有显著影响。
