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New paper: Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence

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  • Laurel Schaider
    Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence   Laura E. Erban, Steven M. Gorelick, Howard A.
    Message 1 of 1 , Sep 10 6:34 AM
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      Release of arsenic to deep groundwater in the Mekong Delta , Vietnam , linked to pumping-induced land subsidence
       
      Laura E. Erban, Steven M. Gorelick, Howard A. Zebker, and Scott Fendorf
      Proceedings of the National Academy of Sciences.  110 (34): 13751-13756.
       
       
      Abstract
       
      Deep aquifers in South and Southeast Asia are increasingly exploited as presumed sources of pathogen- and arsenic-free water, although little is known of the processes that may compromise their long-term viability. We analyze a large area (>1,000 km2) of the Mekong Delta , Vietnam , in which arsenic is found pervasively in deep, Pliocene–Miocene-age aquifers, where nearly 900 wells at depths of 200–500 m are contaminated. There, intensive groundwater extraction is causing land subsidence of up to 3 cm/y as measured using satellite-based radar images from 2007 to 2010 and consistent with transient 3D aquifer simulations showing similar subsidence rates and total subsidence of up to 27 cm since 1988. We propose a previously unrecognized mechanism in which deep groundwater extraction is causing interbedded clays to compact and expel water containing dissolved arsenic or arsenic-mobilizing solutes (e.g., dissolved organic carbon and competing ions) to deep aquifers over decades. The implication for the broader Mekong Delta region, and potentially others like it across Asia , is that deep, untreated groundwater will not necessarily remain a safe source of drinking water.
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