Arsenic speciation in Mono lake, California:: Response to seasonal stratification and anoxia
Arsenic speciation in Mono lake, California:: Response to seasonal stratification and anoxia
复制标题
DOI：
10.1016/j.gca.2004.10.011
复制
发表时间：
2005-04-15
影响因子：
5
通讯作者：
Wallschläger, D
中科院分区：
文献类型：
--
作者：
Hollibaugh, JT;Carini, S;Wallschläger, D
莫诺湖（Mono Lake）是一个封闭的碱性高盐湖，位于加州东部大盆地的西部边缘。2002年2月至11月，我们研究了砷（As）的形态分布在莫诺湖的水柱。这一时期捕获的季节性进程，从冬季混合，通过夏季热分层，秋季翻转。采用离子色谱-电感耦合等离子体质谱法对野外液氮速冻保存的样品中砷的形态进行了测定。我们发现，砷形态占主导地位（> 90%）的砷酸盐时，氧是可检测的。一旦水平下降到6 μ mol/L O-2以下，砷的形态转化为优势减少物种。砷酸盐和亚砷酸盐共同发生在一个过渡区直接低于基地的氧跃层和低，但显着浓度的砷酸盐偶尔检测到硫化物的低层样品。硫砷物种的主要形式发现在硫化物沃茨。随着硫化物浓度的增加，硫代砷物种的最大值与化学计量一致的单，二-和三硫代砷相继发生。与三硫代砷的化学计量一致的化合物是占主导地位的物种（类似于50%的总砷）在高硫化物（2 mmol/L）的底层水。底层水中总砷浓度较低，相对于地表水，建议沉淀的As/S矿物相，在长期缺氧过程中硫化物积累。版权所有（c）2005 Elsevier Ltd
Mono Lake is a closed-basin, alkaline, hypersaline lake located at the western edge of the Great Basin in eastern California. We studied the distribution of arsenic (As) species in the water column of Mono Lake between February and November, 2002. This period captured the seasonal progression from winter mixing, through summer thermal stratification, to autumn overturn. Arsenic speciation was determined by ion chromatography-inductively coupled-plasma-mass spectrometry of samples preserved in the field by flash-freezing in liquid nitrogen. We found that arsenic speciation was dominated (> 90%) by arsenate when oxygen was detectable. Once levels fell below 6 mu mol/L O-2, arsenic speciation shifted to dominance by reduced species. Arsenate and arsenite co-occurred in a transition zone immediately below the base of the oxycline and low but significant concentrations of arsenate were occasionally detected in sulfidic hypolimnion samples. Thio-arsenic species were the dominant form of As found in sulfidic waters. Maxima of thio-arsenic species with stoichiometries consistent with mono-, di- and trithio-arsenic occurred in succession as sulfide concentration increased. A compound with a stoichiometry consistent with trithio-arsenic was the dominant As species (similar to 50% of total As) in high sulfide (2 mmol/L) bottom water. Lower concentrations of total As in bottom water relative to surface water suggest precipitation of As/S mineral phases in response to sulfide accumulation during prolonged anoxia. Copyright (c) 2005 Elsevier Ltd