Linking land subsidence to deep arsenic release in the Mekong Delta aquifer system

将地面沉降与湄公河三角洲含水层系统深层砷释放联系起来

• 批准号: 1313518
• 负责人: Steven Gorelick
• 金额: $ 25.64万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-15 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1313518&HistoricalAwards=false
• 关键词: Linking; land; subsidence; deep; arsenic

An estimated 100 million people living in floodplains in Asia are exposed to arsenic in groundwater that is derived from Himalayan sediments. Arsenic is a toxin linked to cancer and a variety of other serious ailments through direct ingestion of contaminated groundwater. Growing exploitation of these contaminated aquifers increases the number of people facing these health risks, and exposes still greater populations to the hazard of consuming agricultural products irrigated with arsenic-contaminated groundwater. Despite widespread awareness of the arsenic hazard, understanding of the relationship between groundwater exploitation and arsenic contamination remains limited, particularly in deep aquifers, which are increasingly providing a larger portion of total pumped groundwater.In this work, we focus on the Mekong Delta, where we have obtained a comprehensive, unique, unanalyzed dataset consisting of 42,000 dissolved arsenic measurements from southern Vietnam showing widespread contamination (1000 sq km) in deep aquifers (200m) that are used extensively for water supply. One hypothesis is that deep pumping has induced shallow dissolved arsenic or arsenic-mobilizing solutes to move deeper. However, preliminary analysis does not support this mechanism in the Mekong Delta given the observed widespread deep arsenic contamination in the presence of thick clay deposits that serve as relative vertical flow barriers. We hypothesize a previously unrecognized deep arsenic source mechanism in which water containing arsenic is expelled from storage in clays that compact when overlying and underlying deep aquifers are exploited. This work combines spatial statistical modeling of groundwater arsenic observations, 3D aquifer flow and compaction simulation, and remote measurement of land subsidence using satellite radar imagery (InSAR). Our goal is to explore the notion that deep groundwater arsenic may be due to the release of pore-waters containing arsenic trapped in clay beds deposited millions of years ago. This research has important implications to science and society. First, our formerly unrecognized contamination mechanism may be fundamental to understanding arsenic occurrence in aquifer systems and the associated health risks of deep groundwater exploitation. Our investigation will have implications for water resources development and human health in the arsenic-affected basins of Southeast Asia where some regions of planned deep aquifer exploitation may unknowingly expose people to deep-source arsenic. This work has consequences for analogous arsenic-affected aquifer systems in sedimentary basins around the world containing interbedded compressible clays that may harbor arsenic and other contaminants. Second, in terms of methods, the link between subsidence and arsenic release has significant potential as a reconnaissance tool, particularly in underdeveloped regions where the impacts of excessive pumping on land subsidence have not been recognized. The use of satellite radar to detect land deformation can serve as a means to identify areas where clay compaction and consequent arsenic release may be occurring.

据估计，居住在亚洲洪泛区中的1亿人暴露于地下水中的砷，这些砷来自喜马拉雅沉积物。砷是通过直接摄入受污染的地下水与癌症和其他各种严重疾病相关的毒素。对这些受污染的含水层的剥削日益增加，增加了面临这些健康风险的人数，并使人口更大，面临着消费用砷污染的地下水灌溉的农产品的危害。尽管人们对砷危害的认识很广泛，但对地下水剥削和砷污染之间关系的理解仍然有限，尤其是在深层含水层中，越来越多地提供了较大的总泵送地下水的部分。在这项工作中，我们专注于乳房达尔塔（Mekong Delta），我们已经通过众多的，众多的，众多的，众多的量子级别的菜单，是众所周知的42,000，422,422,422,422,422,422,4222,422,200越南在深含水层（200m）中显示出广泛的污染（1000平方公里），这些污染物广泛用于供水。一个假设是，深水泵种引起了浅溶解的砷或砷溶质的溶质，以更深地移动。然而，鉴于在存在厚厚的粘土沉积物的存在下，初步分析不支持湄公河三角洲的这种机制，这些污染物是相对垂直流动屏障的厚粘土沉积物。我们假设一种先前未知的深砷源机制，其中含有砷的水是从粘土中排出的，这些粘土的储存在上覆盖和下层深层含水层时被利用。这项工作结合了地下水砷观测，3D含水层流和压实模拟的空间统计模型，并使用卫星雷达成像（INSAR）对土地沉降进行了远程测量。我们的目标是探索一个观念，即深下的地下水砷可能是由于释放了被困在数百万年前的粘土床中的砷含量。 这项研究对科学和社会具有重要意义。首先，我们以前无法识别的污染机制可能是理解含水层系统中砷发生的基础，以及深层地下水剥削的相关健康风险。我们的调查将对以砷影响的东南亚盆地的水资源开发和人类健康产生影响，在那里，一些计划中的深水含水层剥削区域可能在不知不觉地将人们暴露于深层砷中。这项工作对世界各地的沉积盆地中类似的砷影响的含水层系统产生了影响，其中包含可能含有砷和其他污染物的可压缩粘土。 其次，就方法而言，沉降与砷释放之间的联系具有巨大的潜力作为侦察工具，尤其是在尚未确认过多抽水对土地沉降的影响的欠发达地区。使用卫星雷达检测土地变形可以用作确定可能发生粘土压实和随之而来的砷释放区域的一种手段。