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首页> 外文学位 >Geochemical investigation of tungsten in two groundwater flow systems: The Carrizo Sand Aquifer, Texas, USA, and the Aquia Aquifer, Maryland, USA.
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Geochemical investigation of tungsten in two groundwater flow systems: The Carrizo Sand Aquifer, Texas, USA, and the Aquia Aquifer, Maryland, USA.

机译：两种地下水流动系统中钨的地球化学研究：美国德克萨斯州的卡里佐砂含水层和美国马里兰州的阿基亚含水层。

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摘要

Groundwater sampled were collected from well sites located within the Carrizo Sand aquifer in Atascosa and McMullen counties in Texas, and also within the Aquia Aquifer, Maryland in the counties of Queen Anne's, Kent, and Ann Arundel in Maryland. During the field sampling trips, on site measurements were conducted for pH, specific conductance, temperature, alkalinity, dissolved oxygen (DO), oxidation-reduction potential (Eh), iron speciation ([Fe (II)/Fe(III)]), and dissolved S (-II) concentrations. In order to examine and study solid phase tungsten concentrations in the Aquia (archived at the Maryland Geological Survey) and Carrizo Aquifer sediments, we collected a number of aliquots, including duplicates, from pre-existing drill cores (Evergreen Underground Water Conservation District, Pleasenton, TX; Maryland Geological Survey, Baltimore, MD). Tungsten concentrations in the Carrizo Sand Aquifer range from 3.64 to 1297 pmol kg-1 with the lowest concentrations reported from the recharge area followed by progressively increasing dissolved W concentrations with flow downgradient along the flow path. Total tungsten in the Aquia aquifer varies along the flow path ranging from 14.31 to 184.41 pmol kg-1, with an average concentration of 80.41 pmol kg-1. We suggest that increases in W concentrations in our groundwaters are reflective of pH-related desorption. Given that the chemistry of tungsten is very similar to that of Molybdenum, and also that the Carrizo groundwaters contain high levels of S(-II), we suggest that the possible formation of thiotungstates could most likely be responsible for the high tungsten levels in these groundwaters. Again, as was the case with our Aquia sediment samples, the high concentrations of tungsten in the last two fractions of our experiment are in accordance with these studies, and suggest that tungsten is being released into solution under oxidizing conditions. Evolution of W in the Aquia aquifer suggests the element's conservative behavior in these generally oxic to suboxic groundwaters. The observed changes of W concentrations along the studied flow path is also consistent with some direct control due the moderately changing redox conditions in the aquifer, i.e from oxic, to suboxic conditions. We suggest therefore that for W dissolution in groundwaters, pH related adsorption desorption reactions are the key controlling factors in oxic, and sub-oxic waters. Our results also suggest that except for the first few sediment samples, most of the W in the Aquia sediments are bound up in Al-silicate minerals, and are therefore not available for recycling in the groundwaters.
机译：从位于Atascosa的Carrizo砂含水层和得克萨斯州的McMullen县以及马里兰州安妮女王，肯特郡和Ann Arundel县的马里兰州的Aquia含水层内的井场采集了地下水。在野外采样过程中，对pH，比电导，温度，碱度，溶解氧（DO），氧化还原电位（Eh），铁形态（[Fe（II）/ Fe（III）]）进行了现场测量。 ，以及溶解的S（-II）浓度。为了检查和研究Aquia（在马里兰州地质调查局存档）和Carrizo Aquifer沉积物中的固相钨浓度，我们从预先存在的钻芯（常绿地下水保护区，Pleasenton）中收集了许多等分试样，包括重复试样，德克萨斯州；马里兰州地质调查局，马里兰州巴尔的摩）。 Carrizo砂含水层中的钨浓度范围为3.64至1297 pmol kg-1，从补给区报告的最低浓度，然后随着沿流动路径的流速逐渐降低而逐渐增加溶解的W浓度。 Aquia含水层中的总钨沿流径变化范围为14.31至184.41 pmol kg-1，平均浓度为80.41 pmol kg-1。我们认为，地下水中W浓度的增加反映了与pH有关的解吸。鉴于钨的化学性质与钼非常相似，并且卡里佐（Carrizo）地下水含高水平的S（-II），因此我们建议可能形成硫钨酸盐的原因可能是这些钨中的高钨含量地下水。同样，与我们的阿奎亚（Aquia）沉积物样品一样，实验的最后两个部分中的高浓度钨与这些研究一致，表明钨在氧化条件下释放到溶液中。含水层含水量中W的演变表明，在这些通常为有氧至亚低氧的地下水中，元素的保守行为。由于含水层中氧化还原条件的适度变化，即从有氧到低氧条件，沿研究流径观察到的W浓度变化也与某些直接控制相一致。因此，我们建议，对于W在地下水中的溶解，pH相关的吸附解吸反应是含氧和亚含氧水中关键的控制因素。我们的结果还表明，除了前几个沉积物样本外，阿基亚沉积物中的大部分W都被铝硅酸盐矿物束缚，因此无法在地下水中循环利用。

著录项

  • 作者

    Dave, Heeral B.;

  • 作者单位

    The University of Texas at Arlington.;

  • 授予单位 The University of Texas at Arlington.;
  • 学科 Geochemistry.
  • 学位 M.S.
  • 年度 2008
  • 页码 63 p.
  • 总页数 63
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;
  • 关键词

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