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.
Elevated groundwater arsenic (As) concentrations impact the health of over 100 million villagers across Pakistan, Nepal, India, Bangladesh, Myanmar, Cambodia, Vietnam, and China who rely on tubewells as their main source of drinking water. A group of 44 scientists and students from 14 countries met on April 25-27, 2011 in Hanoi, Vietnam to set the stage for a new continental drilling program focused on the groundwater As problem in Asia (www.icdp-online.org/front_content.php?idcat=1580). Half of the participants in this workshop sponsored by International Scientific Continental Drilling Program (ICDP) and the US National Science Foundation (NSF) were from low and lower-middle income countries directly facing the health threat due to elevated As levels in groundwater. There was broad agreement among participants that the dissolution of iron oxides in aquifer sediment that are enriched in As is a key process leading to widespread occurrence of As in shallow groundwater across South, Southeast, and East Asia. However, participants also pointed to the lack of scientific understanding needed to address the issue of greatest societal relevance which is the vulnerability of those aquifers that are currently low in As. This is a crucial question from a public health perspective because selectively tapping low-As aquifers is the most effective way of lowering As exposure. Workshop participants agreed that a decade-long integrated research program may be required to identify the mechanisms that are most relevant to predicting the fate of low-As aquifers. Such a multi-year and multi-country program would be unprecedented in continental scientific drilling and will require supplemental funding beyond ICDP and NSF, as well as a strong governance structure for prioritizing study sites, ensuring broad participation, standardizing methods, and archiving (in some cases freezing) samples for future study.
