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Arsenic in fractured bedrock aquifers in greater Augusta, Maine, USA.

机译：美国缅因州大奥古斯塔破裂基岩含水层中的砷。

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摘要

Thirty one percent of private well water samples (n=790) collected in 2006 from fractured meta-sedimentary bedrock aquifers in greater Augusta, Maine were found to contain >10 mug/L of arsenic. An additional 331 samples were obtained in 2007 from 4 towns representing low to high arsenic occurrence. The spatial pattern of groundwater arsenic distribution resembled the bedrock map. Arsenic exceedance rate was highest in the Silurian pelite and sandstone/limestone (∼40%), and differed significantly from those in the Silurian-Ordovician sandstone (24%), the Devonian granite (15%) and the Ordovician-Cambrian volcanic rocks (9%). This was confirmed in the 4 cluster areas with a greater sampling density. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at scales of 100-101 km.;The elevated arsenic concentrations were associated with high pH, fluoride, molybdenum, and low dissolved oxygen, nitrate, chloride. A logistic regression model showed that bedrock geology, soil arsenic content, pH, dissolved oxygen, nitrate and sulfate played important roles on groundwater arsenic concentrations. Water geochemistry suggested a complex mobilization mechanism of oxidation of arsenic-rich sulfide, adsorption on iron minerals, pH-dependent desorption of arsenic from iron minerals with calcite dissolution along the groundwater flow path.;Geophysical logging and water sampling from bore hole and specific fractures in two wells in Manchester, Maine found that dissolved arsenic concentrations increased when the bore hole water was replaced by the water with high dissolved arsenic coming primarily from high yielding fractures near the bottom of bore hole in response to pumping. Iron particulate precipitates were common and found to be enriched in arsenic. Laboratory experiment suggested that in the bore hole arsenic was mainly settled with iron enriched particles, probably amorphous ferric oxyhydroxides, with possibly minor adsorption on the iron minerals.;The association of arsenic distributions in groundwater, soil and stream sediment from national data sets examined by logistic regression models suggested that soil and stream sediment arsenic distributions had significant effects on groundwater arsenic occurrence at the national scale. Stronger correlations were found in Florida, New England and Nevada at regional scales and in greater Augusta, Maine at the local scale with higher sampling density.
机译：2006年，从缅因州大奥古斯塔破碎的准沉积基岩含水层中收集的私人井水样本（n = 790）中有31％被发现含有> 10杯/升的砷。 2007年从4个城镇中分别采集了331个样品，这些样品分别代表了低砷到高砷的发生。地下水砷分布的空间格局类似于基岩图。志留系泥质和砂岩/石灰岩中的砷超标率最高（〜40％），与志留纪-奥陶纪砂岩（24％），泥盆纪花岗岩（15％）和奥陶纪-寒武纪火山岩（ 9％）。在具有较高采样密度的4个群集区域中已确认了这一点。因此，基岩地质与研究区域100-101 km范围内裂隙基岩含水层中的砷发生有关;砷浓度升高与高pH，氟化物，钼和低溶解氧，硝酸盐，氯化物有关。 Logistic回归模型表明，基岩地质，土壤砷含量，pH，溶解氧，硝酸盐和硫酸盐对地下水砷浓度起着重要作用。水地球化学表明富集硫化物的氧化，铁矿物质上的吸附，pH依赖的铁矿物质中砷的解吸以及沿方解石沿地下水流路的迁移的复杂动员机制;地球物理测井和钻孔和特定裂缝的取水在曼彻斯特的两口井中，缅因州发现，用井眼中的水代替井眼中的高溶解砷的水后，溶解砷浓度会增加，这主要是由于抽水导致井眼底部附近的高产裂缝引起的。铁颗粒沉淀是常见的，并发现富含砷。实验室实验表明，在井眼中，砷主要沉降在富铁颗粒中，可能是无定形的羟基氧化铁，对铁矿物质的吸附可能很小;根据国家数据集对地下水，土壤和河流沉积物中砷分布的关联进行了研究。 Logistic回归模型表明，在全国范围内，土壤和河流沉积物中的砷分布对地下水中砷的产生具有重大影响。在佛罗里达州，新英格兰州和内华达州，在区域尺度上发现了更强的相关性；在缅因州的奥古斯塔州，在当地尺度上发现了更强的相关性，具有更高的采样密度。

著录项

  • 作者

    Yang, Qiang.;

  • 作者单位

    City University of New York.;

  • 授予单位 City University of New York.;
  • 学科 Environmental Geology.;Environmental Sciences.;Geochemistry.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 157 p.
  • 总页数 157
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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