Workshop proposal: Recovering Uncompromised Samples of Aquifer Sands with In-Situ Groundwater from up to 300-m Depth in South and Southeast Asia

地下水含水层是全世界约20亿人饮用水的主要来源。然而，长期暴露于可从未受污染的沉积物中释放到地下水中的天然地质污染物的公共卫生问题日益引起关注。目前被认为对健康有重大影响的未经处理地下水的天然成分包括氟、锰，尤其是南亚和东南亚的砷。调节这些潜在有毒成分释放的地下水和沉积物特性在垂直和横向上往往变化很大。这种高度的空间变异性，再加上缺乏在不接触钻井液或大气氧气的情况下同时对地下水和含水层砂进行采样的技术，是难以分离出生物地球化学和水文因素的关键原因。克服这一限制的一个有希望的途径是增加一个原位冷冻包，在岩心底部形成一个塞，这些岩心是用DOSECC（地球钻探、观察和采样）开发的现有钢丝绳钻井工具收集的。美国大陆地壳公司（Continental Crust Inc.）是一家由国家科学基金会部分支持的非营利性公司。这项提案是对国际大陆科学钻探计划现有的讲习班赠款的一项补充请求，以开发必要的采样技术，并制定一项科学计划，以便在未来十年部署新技术。通过类比物理学中的大型实验，独特技术的可用性可以促进地球科学家社区内的合作水平，这比过去的分散努力更适合于理解复杂的环境问题，如南亚和东南亚的地下水砷问题。受影响地区的缓解工作继续受到从深层低砷含水层抽水的可持续性的不确定性的阻碍，这些含水层越来越多地被用来为数百万村民提供安全饮用水。拟议的技术将有助于减少这种不确定性，随后可用于与地下水质量有关的其他问题的研究。

Groundwater aquifers are the main source of drinking water for about 2 billion people worldwide. There is, however, growing public health concern about chronic exposure to natural, geogenic contaminants that can be released from uncontaminated sediment to groundwater. Natural constituents of untreated groundwater currently recognized to be of significant health concern include fluoride, manganese, and particularly arsenic in South and Southeast Asia. The groundwater and sediment properties that regulate the release of these potentially toxic constituents are often highly variable both vertically and laterally. This high degree of spatial variability combined with a lack of technology for sampling groundwater and aquifer sands simultaneously without exposure to drilling fluid or atmospheric oxygen are a key reason that contributing biogeochemical and hydrological factors have been difficult to isolate. A promising avenue for overcoming this limitation is the addition of an in situ freezing package to form a plug at the bottom of a core collected with existing wire-line drilling tools developed by DOSECC (Drilling, Observation and Sampling of the Earth?s Continental Crust Inc.), a not-for-profit corporation supported in part by the National Science Foundation. This proposal is a request to supplement an existing workshop grant from the International Continental Scientific Drilling Program to develop the necessary sampling technology and to generate a science plan for deploying the new technology over the next ten years. By analogy to large experiments in physics, the availability of unique technology could foster the level of collaboration within a community of geoscientists that is better suited than disparate efforts of the past to understanding a complex environmental issue such as the groundwater arsenic problem in South and Southeast Asia. Mitigation in the affected region continues to be hampered by uncertainty concerning the sustainability of pumping from deep low-arsenic aquifers that are increasingly tapped to provide safe drinking water to millions of villagers. The proposed technology will contribute to reducing this uncertainty and could subsequently be deployed for research on other issues related to groundwater quality.