Predicting Secular Changes in Arsenic Hazard in Circum-Himalyan Groundwaters

Over 100 million people drink groundwaters containing naturally occurring arsenic (As) higher than the WHO guide value (10 ppb). In Bangladesh alone, 20% of all deaths in impacted areas are attributable to such exposure (ARGOS, 2010) - this corresponds to about 30,000 premature deaths every year.

Studies provide evidence for both in-aquifer and near-surface sediment As sources. ISLAM (2004) demonstrated that As release occurs from within the aquifer sediments & highlighted the importance of organic matter (OM) in this process. BENNER (2008) & POLIZZOTTO (2008) have suggested, instead, that As release mostly occur in near-surface sediments BEFORE entering the aquifer. Determining the relative importance and controls of As release from the near surface sediments (typically 5 m - 15 m depth) from that which occurs within the aquifer, as well as assessing the various controls on As once in solution, are critical if we are to develop the required process oriented understanding of As mobility in drinking water supplies.

Identifying study areas that reveal these processes is hard. For example, massive groundwater abstraction in the densely populated areas of West Bengal and Bangladesh has resulted in a complex subsurface hydrological environment which makes tracking As release mechanisms almost impossible. However, the absence of such extensive abstraction in As-rich aquifers of Cambodia means that this subsurface hydrological environment remains largely unaltered. Recent work by project partners (Stanford) means that a representative high As area has been identified and the hydrogeology established - but not on a scale or with the geochemical techniques required to establish a full understanding.

We will drill 77 new and relatively inexpensive boreholes at the Cambodian site after using geophysics (supplied by our BGS partner) to determine the best locations. These new wells will allow us to collect samples across established As hotspots at a scale over which the As release process must be operating. Three well nests will sample an oxbow lake overlying an As contaminated aquifer, a sand 'window' through the overlying clay sediments and a control through the clay sediment overlying the As contaminated main aquifer. Two further well sequences will allow sampling of the main aquifer along its flow path. A 5-20m tube-well separation represents ~5-250 years of aquifer chemical evolution. Our Cambodian partners at RUPP & RDI will give local logistic support.

We have been working closely our NERC Radiocarbon Lab partner. We show within our proposal that 14-C dating of organic matter in sediments and of dissolved inorganic and organic carbon in groundwaters provides a profound technique for identifying organic matter sources, central to resolving As release mechanisms. Similarly, pilot work withour NERC stable isotope facility partner has shown the utility of applying delta-18O and delta-D data to quantify surface water input into the main aquifer. Both of these approaches, combined with Manchester anion, cation and inorganic assay of sediments as well as tritium and 4-He techniques to date any young water input or ancient fluid contribution, will provide a fully comprehensive geochemical approach. With the high spatial resolution of sampling we expect this approach to make a major contribution in: i) quantifying the flux of As on a spatial scale alongside secular changes in As hazard from these two potential As sources; ii) identifying the dominant source of OM responsible for driving As release from these locations; and iii) identifying the controlling processes and mechanisms responsible for As release in these profiles. Together this understanding will enable the development of a quantitative model with predictive capacity that will inform governmental agencies responsible for drinking water and irrigation supplies to assess how continuation of, or changing, water use practice will impact future water supply As risks.

Beside academic researchers (see academic beneficiaries), the research outcomes will be of interest to:

[1] Groundwater resource stakeholders: government organisations & NGOs who have responsibilities, authority and/or interests in protecting public health in the regions impacted should have interests in the research - particularly as it informs predictions of secular increases in groundwater arsenic hazard - proper and informed utilization of well communicated relevant project outcomes may ultimately benefit millions of people

[2] In addition, we recognize a responsibility to undertake broader range outreach to inform, educate and involve a wider spectrum of society, particularly in regions impacted by groundwater arsenic

We will use a range of activities tailored to best effectively impact the different major target groups:

[1] Groundwater resource stakeholders

a. We will email/write to key stakeholders, particularly in Cambodia, Vietnam, India, Bangladesh & China, with lay summaries of our key findings

b. We will make further personal contacts with key government & NGO officers & through a short workshop in Phnom Penh, Cambodia in the final year of the project to highlight key relevant findings

For these activities we will build upon networking links &collaborations established through the AquaTRAIN MRTN (pan European), EU Asia-Link CALIBRE (SE Asia) and UKIERI PRAMA (India) networks all coordinated by the PI. Key stakeholder representatives engaged in our UKIERI PRAMA workshops have included the Chair, Government of West Bengal (GoWB) Arsenic Task Force and the Chief Engineer of the GoWB PHED (Public Health Engineering Directorate), responsible for implementing the substantial part of a £300,000,000 arsenic mitigation programme in that state. Our EU Asia-Link CALIBRE workshops in Phnom Penh & Vientiane have to date delivered CPD training to over 50 environmental professionals from a wide variety of government organisations and NGOs in Cambodia & Lao PDR respectively.

[2] General public - in groundwater arsenic impacted regions & in UK

a. Website, as above but with content specifically targeted at non-science readers. The key components will be to give a description of our approach, the methods used and the results obtained in a user-friendly and accessible way. All educational material as a result of other activities, such as the workshop, our UK outreach programme and the video (see below), will be made freely available through this website.

b. Press releases: Key research results will be communicated in lay terms through press releases via the University Press Office (after, as appropriate, liaising with the NERC press office) and through other media, including TV and radio. Our work on arsenic biogeochemistry (and also on CO2 sequestration) has already attracted considerable media attention over the last 5 years, with many newspaper and web articles as well as radio interviews, including recently in the France equivalent of New Scientist, Pour Le Science (Millot, Charlet & Polya, 2011)

c. Cambodia Outreach, we will engage in Outreach Activities, in collaboration with the our NGO partner RDI who have a long and successful track record of such engagement at national, provincial and local levels. This will build upon activities already undertaken as part of the EU Asia-Link CALIBRE Project, to which RDI was an Associate Partner. Specifically we will assist in the production of a video that can be used in these activities and in the support in activities piggy-backing on RDI's existing programme of outreach to arsenic-impacted villages.

d. UK Outreach: We will participate in public events, including the University of Manchester Science Showcase week, open programme lecturing at The Manchester Museum and/or assisting in running workshops on public engagement in Science. We are currently collaborating with the UK Health Protection Agency on public exposures to arsenic in SW England.