Ou Ling, Gannon Travis W, Polizzotto Matthew L
Department of Botany and Plant Pathology, Purdue University, 915 W State St, West Lafayette, IN, 47907, United States.
Department of Crop and Soil Sciences, North Carolina State University, 101 Derieux Pl, Raleigh, NC 27695, United States.
Chemosphere. 2017 Nov;186:243-250. doi: 10.1016/j.chemosphere.2017.07.147. Epub 2017 Jul 28.
Monosodium methyl arsenate (MSMA), a common arsenical herbicide, is a major contributor of anthropogenic arsenic (As) to the environment. Uncertainty about controls on MSMA fate and the rates and products of MSMA species transformation limits effective MSMA regulation and management. The main objectives of this research were to quantify the kinetics and mechanistic drivers of MSMA species transformation and removal from solution by soil. Laboratory MSMA incubation studies with two soils and varying soil organic carbon (SOC) levels were conducted. Arsenic removal from solution was more extensive and faster in sandy clay loam incubations than sand incubations, but for both systems, As removal was biphasic, with initially fast removal governed by sorption, followed by slower As removal limited by species transformation. Dimethylarsinic acid was the dominant product of species transformation at first, but inorganic As(V) was the ultimate transformation product by experiment ends. SOC decreased As removal and enhanced As species transformation, and SOC content had linear relationships with As removal rates (R = 0.59-0.95) for each soil and reaction phase. These results reveal the importance of edaphic conditions on inorganic As production and overall mobility of As following MSMA use, and such information should be considered in MSMA management and regulatory decisions.
甲基胂酸单钠（MSMA）是一种常见的含砷除草剂，是环境中人为来源砷的主要贡献者。MSMA归宿的控制以及MSMA物种转化的速率和产物存在不确定性，这限制了对MSMA的有效监管和管理。本研究的主要目的是量化MSMA物种转化的动力学和机制驱动因素，以及土壤对溶液中MSMA的去除情况。开展了在两种土壤以及不同土壤有机碳（SOC）水平下进行的MSMA实验室培养研究。在砂质粘壤土培养中，溶液中砷的去除比砂质培养更为广泛和迅速，但对于这两种体系，砷的去除均呈双相，最初快速去除受吸附控制，随后较慢的砷去除受物种转化限制。起初，二甲基胂酸是物种转化的主要产物，但到实验结束时，无机砷（V）是最终的转化产物。SOC降低了砷的去除并增强了砷的物种转化，并且每种土壤和反应阶段的SOC含量与砷去除率呈线性关系（R = 0.59 - 0.95）。这些结果揭示了土壤条件对使用MSMA后无机砷产生及砷整体迁移性的重要性，在MSMA管理和监管决策中应考虑此类信息。
