• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文OA文献 >Flow and sorption controls of groundwater arsenic in individual boreholes from bedrock aquifers in central Maine, USA
【2h】

Flow and sorption controls of groundwater arsenic in individual boreholes from bedrock aquifers in central Maine, USA

机译：美国缅因州中部基岩含水层中单个钻孔中地下水砷的流量和吸附控制

页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

To understand the hydrogeochemical processes regulating well water arsenic (As) evolution in fractured bedrock aquifers, three domestic wells with [As] up to 478 μg/L are investigated in central Maine. Geophysical logging reveals that fractures near the borehole bottom contribute 70–100% of flow. Borehole and fracture water samples from various depths show significant proportions of As (up to 69%) and Fe (93–99%) in particulates (> 0.45 μm). These particulates and those settled after a 16-day batch experiment contain 560–13,000 mg/kg of As and 14–35% weight/weight of Fe. As/Fe ratios (2.5–20 mmol/mol) and As partitioning ratios (adsorbed/dissolved [As], 20,000–100,000 L/kg) suggest that As is sorbed onto amorphous hydrous ferric oxides. Newly drilled cores also show enrichment of As (up to 1300 mg/kg) sorbed onto secondary iron minerals on the fracture surfaces. Pumping at high flow rates induces large decreases in particulate As and Fe, a moderate increase in dissolved [As] and As(III)/As ratio, while little change in major ion chemistry. The δD and δ18O are similar for the borehole and fracture waters, suggesting a same source of recharge from atmospheric precipitation. Results support a conceptual model invoking flow and sorption controls on groundwater [As] in fractured bedrock aquifers whereby oxygen infiltration promotes the oxidation of As-bearing sulfides at shallower depths in the oxic portion of the flow path releasing As and Fe; followed by Fe oxidation to form Fe oxyhydroxide particulates, which are transported in fractures and sorb As along the flow path until intercepted by boreholes. In the anoxic portions of the flow path, reductive dissolution of As-sorbed iron particulates could re-mobilize As. For exposure assessment, we recommend sampling of groundwater without filtration to obtain total As concentration in groundwater.
机译：为了了解调节裂隙基岩含水层中井水砷（As）演化的水文地球化学过程，在缅因州中部研究了三口[As]高达478μg/ L的家用井。地球物理测井表明，井底附近的裂缝占流量的70％至100％。在不同深度的钻孔和压裂水样品中，颗粒（> 0.45μm）中的As（高达69％）和Fe（93-99％）占很大比例。这些颗粒物和经过16天批量试验后沉降的颗粒物包含560-13,000 mg / kg的As和14-35％的重量/重量的Fe。 As / Fe比（2.5–20 mmol / mol）和As分配比（吸附/溶解[As]，20,000–100,000 L / kg）表明As被吸附到无定形含水三氧化二铁上。新钻的岩心还显示出富集的砷（高达1300 mg / kg）吸附在断裂表面的次生铁矿物上。以高流速泵送会导致颗粒中的As和Fe大量减少，溶解的[As]和As（III）/ As比值适度增加，而主要离子化学变化很小。钻孔和压裂水的δD和δ18O相似，表明大气降水产生的补给来源相同。结果支持了在裂隙基岩含水层中对地下水[As]进行流量和吸附控制的概念模型，其中氧的渗透促进了流道含氧部分中较浅深度的含As硫化物的氧化，从而释放了As和Fe。然后进行Fe氧化形成氢氧化羟基Fe颗粒，这些颗粒在裂缝中运输并沿流路吸附As，直到被井孔拦截为止。在流道的缺氧部分中，As吸附的铁颗粒的还原溶解可能使As重新迁移。对于暴露评估，我们建议对地下水进行采样而不进行过滤，以获得地下水中总砷浓度。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利

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