Natural occurrence of hexavalent chromium in the aromas red sands aquifer, California
Natural occurrence of hexavalent chromium in the aromas red sands aquifer, California
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DOI：
10.1021/es048835n
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发表时间：
2005-08-01
影响因子：
11.4
通讯作者：
Flegal, AR
中科院分区：
文献类型：
--
作者：
Gonzalez, AR;Ndung'u, K;Flegal, AR
为解决圣克鲁斯县饮用水中铬污染日益严重的问题，我们设计了一项研究，调查当地含水层中铬浓度和形态的来源和空间梯度。Soquel CreekWater区的一份报告（2001年1月）催化了这项研究，该报告称，在Aromas Red Sands含水层中，六价铬浓度升高，范围从6 μ g L-1到36 μ g L-1，接近该州的最大浓度限值50 μ g L-1。为了测试这些初步测量的准确性，我们收集了地下水使用微量金属清洁技术从11个地点在圣克鲁斯县，包括10个从含水层，据报道，铬浓度升高和1个从邻近的含水层，普里西马，并分析了他们的总铬使用电感耦合等离子体质谱法。据报告，10个污染场地中有9个场地的总铬浓度范围为5至39 μ g L-1，而对照场地的一个场地低于检测限（0.01 μ g L-1）。我们还测量了铬的形态在所有网站使用固体支撑膜提取结合石墨炉原子吸收光谱法，并确定平均84%的总铬是铬（VI）。除了地下水分析外，还对Aromas Red Sands和Purisima含水层的沉积物样品进行了一系列提取。这些测试被用来经验性地表征沉积物中的痕量金属（铬，铁，锰）分布在五个阶段提供有关这些痕量金属的起源，可用性，反应性和动员的信息。从地下水和沉积物样品的结果表明，铬是天然存在的芳香红砂含水层，可能是由铬（III）矿床被氧化为铬（VI）的锰氧化物在含水层。
To address increasing concerns of chromium contamination in the drinking water of Santa Cruz County, we designed a study to investigate the source(s) and spatial gradients of the chromium concentration and speciation in local aquifers. This study was catalyzed by a report (January 2001) by the Soquel CreekWater District of elevated hexavalent chromium concentrations ranging from 6 to 36 mu g L-1, approaching the state's maximum concentration limit of 50 mu g L-1, in the Aromas Red Sands aquifer. To test the accuracy of those preliminary measurements, we collected groundwater using trace metal clean techniques from 11 sites in Santa Cruz County, including 10 from the aquifer with reportedly elevated chromium concentrations and 1 from an adjacent aquifer, the Purisima, and analyzed them for total chromium using inductively couple plasma mass spectrometry. Nine of the reportedly 10 contaminated sites had total chromium concentrations ranging from 5 to 39 mu g L-1, while one from the control site was below the limit of detection (0.01 mu g L-1). We also measured the speciation of chromium at all sites using a solid supported membrane extraction coupled with graphite furnace atomic absorption spectrometry and determined that on average 84% of total chromium was Cr(VI). In addition to the groundwater analyses, a series of extractions were performed on sediment samples from both the Aromas Red Sands and Purisima aquifers. These tests were used to empirically characterize sediment trace metal (Cr, Fe, Mn) distributions in five phases providing information about the origin, availability, reactivity, and mobilization of these trace metals. Results from groundwater and sediment samples indicate that the chromium is naturally occurring in the Aromas Red Sands aquifer, possibly by Cr(III) mineral deposits being oxidized to Cr(VI) by manganese oxides in the aquifer.