Sources, transport, and fate of arsenic in ground water

这项研究的主要目的是表征的来源，运输和命运的地下水系统中的砷在新罕布什尔州已知含有高水平的砷。我们将通过研究新罕布什尔州的四个地理区域来实现这一目标，我们在一项作为试点项目完成的区域调查中发现了这些区域的高砷含量。这将包括砷可能来自地质或人为来源的地区。在我们最近的研究中（Peters et al., 1999），我们测量了从新罕布什尔州随机选择的家庭中收集的992份饮用水样本中的砷浓度。在钻探的基岩井中发现砷含量很高，大约35%的井超过了2克/升，这是美国环保署考虑的新的最大污染物水平标准的最低值。我们确定了砷含量高的四个地理区域，它们都在该州的南半部。对最大的簇（新罕布什尔州的Bow）进行了更详细的研究，发现基岩中的砷含量很高，这是一种容易浸出的形式。在这里提出的研究中，我们希望在地下水系统的水文和地球化学方面仔细研究这四组中的每一组。我们将使用1)基本的水文技术来绘制区域地下水流动模式，2)电子探针x射线作图来确定岩石和土壤中的砷载体相，3)柱实验来测量砷从基岩和土壤中溶解的化学条件，4)特定物种的水化学分析来详细表征地下水系统的氧化还原条件和负责砷迁移的化学机制。5)采用柱形试验测量基岩和土壤的缓蚀特性。为了说明我们对这项研究的方法，我们将在本提案中重点介绍我们已经做了一些初步工作的两个实地地点，这些地点可能代表地质来源与人类来源的砷源的末端成员案例。这项工作的结果将进一步加深我们对含水层和矿山废品区砷的来源和化学的一般认识。我们的研究将集中在以前未被强调的晶体（即花岗岩）地质地质体中的砷污染问题上。我们的工作将提供信息，有助于在新英格兰和其他地方的砷污染结晶基岩地区的管理和补救方面做出更明智的决定。

The main goal of this study is to characterize the sources, transport and fate of arsenic in groundwater systems in New Hampshire which are known to contain high levels of arsenic. We will accomplish this goal by studying each of the four geographic regions within New Hampshire where high arsenic levels were identified by us in a regional survey that was completed as a pilot project. This will include regions where arsenic may be derived from either geologic or human-derived sources. In our recent study (Peters et al., 1999) we measured arsenic concentrations in 992 drinking water samples collected from randomly selected households in New Hampshire. Arsenic was found to be highly elevated in drilled bedrock wells, with approximately 35% of these wells exceeding 2 g/L, which is the lowest value being considered by the USEPA for the new maximum contaminant level standard. We identified four geographic regions with high arsenic levels, all of which are in the southern half of the state. The largest cluster (Bow, NH) was studied in more detail and found to have highly elevated arsenic in bedrock, which was in an easily leachable form. In the study proposed here, we wish to closely investigate each of the four clusters with respect to the hydrology and geochemistry of the groundwater systems. We will use 1) basic hydrologic techniques to map the regional groundwater flow patterns, 2) electron microprobe x- ray mapping to determine arsenic carrier phases in rocks and soils, 3) column experiments to measure the chemical conditions under which arsenic is solubilized from the bedrock and soils, 4) species-specific chemical analyses of waters to characterize in detail the redox conditions of the groundwater system and the chemical mechanisms responsible for arsenic mobility, and 5) column experiments to measure the retardatioin properties of bedrock and soils. For the purposes of illustrating our approach to this study, we will focus in this proposal on two field sites where we have done some preliminary work and which may represent the end-member cases of geologically-derived versus human-derived arsenic sources. Results from this work will further our general knowledge of the sources and chemistry of arsenic in the aquifers and mine waste areas. Our study will concentrate on a previously under-emphasized arsenic contamination problem in crystalline (i.e., granitic) geological teranes. Our work will provide information that will aid in making more informed decisions with respect to the management and remediation of arsenic- contaminated crystalline bedrock regions in new England and elsewhere.