• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Hydrogeochemical evolution of arsenic in groundwater: Sources and sinks in the Mississippi River Valley alluvial aquifer, southeastern Arkansas, United States.
【24h】

Hydrogeochemical evolution of arsenic in groundwater: Sources and sinks in the Mississippi River Valley alluvial aquifer, southeastern Arkansas, United States.

机译：地下水中砷的水文地球化学演化：美国阿肯色州东南部密西西比河谷冲积含水层的来源和汇。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Twenty one of 118 irrigation water wells completed in the shallow (25-30 m thick) Mississippi River Valley alluvial aquifer in the Bayou Bartholomew watershed, southeastern Arkansas had arsenic (As) concentrations (<0.5 to 77 μg/L) exceeding 10 μg/L. Two nested monitoring wells (10 m and 36 m deep) were installed in the vicinity of the highest, median, and lowest concentrations of As at three sites in Jefferson County, Arkansas. Sediment and groundwater samples were collected to characterize the mobilization, transport, and distribution of As in aquifers. A traditional five-step sequential extraction was performed to differentiate the exchangeable, carbonate, amorphous Fe and Mn oxide, organic, and hot HNO3-leachable fraction of As and other compounds in sediments. The Chao extraction removes amorphous Fe and Mn oxides by reductive dissolution and is a measure of reducible Fe and Mn in sediments. The hot HNO3 extraction removes mostly crystalline metal oxides. Significant total As (20%) is complexed with amorphous Fe and Mn oxides in sediments. Arsenic abundance is not significant in carbonates or organic matter. Significant (40-70 μg/Kg) exchangeable As is only present at shallow depth (0-1 m). Arsenic is positively correlated to Fe extracted by Chao reagent (r=0.83) and HNO3 (r=0.85). Increasing depth has a positive relationship (r=0.56) to Fe (II)/Fe (the ratio of Fe concentration in the extracts of Chao reagent and hot HNO3), but it has a negative relationship (r=-0.45) to As extracted by Chao reagent. Fe (II)/Fe is positively correlated (r=0.76) to As extracted from Chao reagent. Although Fe (II)/Fe increases with depth, the relative amount of reducible Fe decreases noticeably with depth. The amount of reducible hydrous Fe oxides (HFO), as well as its complexed As decreases with depth. Possible explanations for the decrease in reducible Fe and its complexed As with depth include historic flushing of As and Fe from HFO and aging of HFO to crystalline phases. As+5, the dominant As-species in groundwater, has positive relations (r=0.84) to decreasing redox (RmV).;Inverse geochemical modeling (PHREEQC) was used to identify the evolution of groundwater with emphasis on As in the research area. The modeling was based on flow paths defined by high-precision (±2 cm) water level contour map; x-ray diffraction (XRD), scanning electron microscopic (SEM), and chemical analysis of boring-sediments for minerals; and detailed chemical analysis of groundwater along the flow paths. Potential phases were constrained using general trends in chemical analyses data of groundwater and sediments, and saturation indices data (MINTEQA2) of minerals in groundwater. Modeling results show that calcite, gypsum, halite, fluorite, Fe oxyhydroxide, organic matter, CO2 (gas), H2S (gas) are dissolving, whereas sphalerite, FeS, siderite, barite, and vivianite are mostly precipitating. Significant amount of sediment sulfide was detected in the aquifer sediments below the water table.;The redox environment, chemical data of sediments and groundwater, and the results of geochemical modeling indicate that reductive dissolution of Fe oxyhydroxide is the dominant process of As release in the groundwater. Gypsum solubility and SO42- reduction with co-precipitation of As and sulfide is an important limiting process controlling the concentration of dissolved As in groundwater. Spatial and temporal variability of As is controlled by spatial distribution and redox status of different redox zones at various depths in the aquifer.;Application of surface complexation models (SCM) to predict the sorption behavior of As and HFO in the laboratory has increased in the last decade. However, the application of SCM to predict the sorption of As or other elements in natural sediments has not been often reported, and such applications are greatly constrained by the lack of site specific model parameters. Attempts have been made to use SCM considering a component-additivity approach which accounts for relative abundances of pure phases in natural sediments, followed by the addition of SCM parameters individually for each phase. Although, few reliable and internally consistent sorption databases related to HFO exist, the use of SCM using laboratory-derived sorption databases to predict the mobility of As or other elements in natural sediments has increased. This study evaluated the ability of the SCM using the geochemical code PHREEQC to predict solid phase As in the sediments of the research area. The SCM option of double layer model (DLM) was simulated using ferrihydrite and goethite as sorbents quantified from chemical extractions; calculated surface site concentrations, published surface properties, and normalized published laboratory-derived sorption constants for the sorbents. The model over predicts extracted As in deeper (21-36.6 m) reduced coarse-sediments 4 to 24-fold. The model predicts 57-92% of extracted As in shallow (0-17 m) relatively oxidized fine-sediments. The model is very sensitive to the speciation of As, and the presence of competitive ions in groundwater.
机译：在阿肯色州东南部的巴约巴塞洛缪流域的密西西比河河谷浅水冲积层中的118口灌溉水井中，有21口井的砷（As）浓度（<0.5至77μg/ L）超过10μg/ L.在阿肯色州杰斐逊县的三个地点，在最高，中值和最低砷浓度附近安装了两个嵌套的监测井（深分别为10 m和36 m）。收集沉积物和地下水样品以表征含水层中砷的迁移，运输和分布。进行传统的五步连续萃取以区分沉积物中As和其他化合物的可交换的碳酸盐，无定形的Fe和Mn氧化物，有机和热的HNO3可浸出部分。 Chao萃取通过还原溶解去除非晶态的Fe和Mn氧化物，是沉积物中可还原的Fe和Mn的量度。 HNO3的热萃取可去除大部分结晶金属氧化物。沉积物中大量的总砷（20％）与非晶态的铁和锰氧化物复合。碳酸盐或有机物中的砷丰度不明显。大量（40-70μg/ Kg）可交换砷仅存在于浅深度（0-1 m）中。砷与Chao试剂（r = 0.83）和HNO3（r = 0.85）提取的Fe呈正相关。深度的增加与Fe（II）/ Fe（Chao试剂和热HNO3的萃取物中的Fe含量之比）成正比关系（r = 0.56），而与As萃取成负相关（r = -0.45）经Chao试剂。 Fe（II）/ Fe与从Chao试剂中提取的As正相关（r = 0.76）。尽管Fe（II）/ Fe随深度增加，但可还原Fe的相对量随深度显着降低。可还原的含水Fe氧化物（HFO）的数量及其络合的As随深度降低。还原性铁及其复杂的砷随深度降低的可能解释包括历史性地将砷和铁从HFO中冲洗出来，以及将HFO老化至结晶相。 As + 5是地下水中的主要As物种，与还原氧化还原（RmV）呈正相关（r = 0.84）.;在研究区中，采用了逆地球化学模型（PHREEQC）来识别地下水的演化，重点是As 。建模基于高精度（±2 cm）水位等高线图定义的流径； X射线衍射（XRD），扫描电子显微镜（SEM）以及矿物沉渣的化学分析；以及沿流动路径的地下水的详细化学分析。使用地下水和沉积物化学分析数据的一般趋势以及地下水中矿物质的饱和指数数据（MINTEQA2）限制了潜在阶段。模拟结果表明，方解石，石膏，岩盐，萤石，羟基氧化铁，有机物，CO2（气体），H2S（气体）溶解，而闪锌矿，FeS，菱铁矿，重晶石和堇青石则大部分析出。在地下水位以下的含水层沉积物中检测到大量的沉积物硫化物。氧化还原环境，沉积物和地下水的化学数据以及地球化学模拟的结果表明，羟基氧化铁的还原溶解是砷释放的主要过程。地下水。石膏的溶解度和与砷和硫化物共沉淀的SO42-还原是控制地下水中溶解的砷浓度的重要限制过程。砷的时空变化受含水层中不同深度处不同氧化还原区域的空间分布和氧化还原状态的控制;在实验室中使用表面络合模型（SCM）来预测砷和HFO在实验室中的吸附行为的应用有所增加。过去十年。然而，SCM预测自然沉积物中As或其他元素的吸附的应用尚未见报道，并且由于缺乏特定地点的模型参数而受到极大的限制。已经尝试使用考虑成分可加性方法的SCM，该方法考虑了天然沉积物中纯相的相对丰度，然后为每个相分别添加了SCM参数。尽管几乎没有与HFO相关的可靠且内部一致的吸附数据库，但是使用SCM和实验室衍生的吸附数据库来预测天然沉积物中As或其他元素的迁移率已经增加。本研究使用地球化学代码PHREEQC评估了SCM预测研究区域沉积物中固相As的能力。双层模型（DLM）的SCM选项是使用三水铁矿和针铁矿作为吸附剂的化学提取方法进行模拟的；计算的表面部位浓度，已发布的表面性质，以及标准化的已发布的实验室衍生的吸附剂吸附常数。该模型过高地预测了较深（21-36.6 m）的粗提物减少了4至24倍的粗提率。该模型预测，浅层（0-17 m）相对氧化的细沉积物中提取的砷占57-92％。该模型对砷的形态以及地下水中竞争性离子的存在非常敏感。

著录项

  • 作者

    Sharif, Md. Salah Uddin.;

  • 作者单位

    University of Arkansas.;

  • 授予单位 University of Arkansas.;
  • 学科 Hydrology.;Geochemistry.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 367 p.
  • 总页数 367
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号