Arsenic distribution, speciation and solubility in shallow groundwater of Owens Dry Lake, California
Arsenic distribution, speciation and solubility in shallow groundwater of Owens Dry Lake, California
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DOI：
10.1016/s0016-7037(02)00897-9
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发表时间：
2002-09
影响因子：
5
通讯作者：
J. Ryu;Suduan Gao;R. Dahlgren;R. Zierenberg
中科院分区：
文献类型：
--
作者：
J. Ryu;Suduan Gao;R. Dahlgren;R. Zierenberg
欧文斯湖干盐湖产生的尘埃颗粒在美国西部造成了严重的空气污染危害。从干燥的湖床产生的大部分灰尘来自于盐水蒸发形成的盐，这些盐通常含有高浓度的溶解砷（As）。本研究的目的是研究浅层地下水中溶解态砷的空间分布，并探讨影响砷溶解度和形态的因素。蒸发浓缩，氧化还原电位，pH值，矿物溶解度进行了研究，作为调节砷的地球化学的因素。溶解态砷的浓度从0.1到96 mg L− 1不等，从湖岸线到湖床中心呈普遍增加趋势。砷浓度与电导率和δD呈显著正相关，表明蒸发浓缩是调节总砷浓度的重要过程。在Eh值小于约-170 mV时，亚砷酸盐[As（III）]是无机砷的主要形式，而在Eh值较高时，砷酸盐[As（V）]是主要形式。浅层地下水中有机砷含量均小于0.21%。溶解的砷浓度似乎不强烈调节固相反应。固相砷浓度一般在4.0至42.6 mg kg− 1之间，当溶液浓度增加到80 mg L−1时，达到最大浓度范围（20至40 mg kg−1），表明砷的吸附和/或沉淀最小。化学平衡模型表明，雌黄（As 2S 3）是唯一的固相具有正饱和指数（表示过饱和），但只有在高砷和硫化物浓度。这项研究的结果是很重要的评估潜在的环境影响，砷浓度升高的降尘工作发生在欧文斯干湖。
Generation of dust particles from the Owens Lake playa creates a severe air pollution hazard in the western United States. Much of the dust produced from the dry lakebed is derived from salts formed by evaporation of saline groundwater that often contains high concentrations of dissolved arsenic (As). The objectives of this research were to study the spatial distribution of dissolved arsenic in the shallow groundwater, and to examine factors affecting arsenic solubility and speciation. Evapoconcentration, redox potential, pH, and mineral solubility were examined as factors regulating arsenic biogeochemistry. Dissolved arsenic concentrations ranged from 0.1 to 96 mg L−1and showed a general increase from the shoreline to the center of the lakebed. Arsenic concentrations were strongly correlated to electrical conductivity (EC) and δD suggesting that evapoconcentration is an important process regulating total As concentrations. Arsenite [As(III)] was the dominant form of inorganic arsenic at Eh values less than about −170 mV while arsenate [As(V)] was predominant at higher Eh values. Organic arsenic was negligible (<0.21%) in all shallow groundwater samples. Dissolved arsenic concentrations do not appear to be strongly regulated by solid-phase reactions. Solid-phase arsenic concentrations generally ranged between 4.0 and 42.6 mg kg−1and a maximum concentration range (20 to 40 mg kg−1) was reached as solution concentration increased up to 80 mg L−1, indicating minimal sorption and/or precipitation of arsenic. Chemical equilibrium modeling indicated that orpiment (As2S3) was the only solid phase with a positive saturation index (indicating over-saturation), but only at high arsenic and sulfide concentrations. The findings of this research are important for assessing the potential environmental impacts of elevated arsenic concentrations on dust mitigation efforts taking place at Owens Dry Lake.