TY - JOUR
T1 - Arsenic contamination of Bangladesh aquifers exacerbated by clay layers
AU - Mihajlov, Ivan
AU - Mozumder, M. Rajib H.
AU - Bostick, Benjamín C.
AU - Stute, Martin
AU - Mailloux, Brian J.
AU - Knappett, Peter S.K.
AU - Choudhury, Imtiaz
AU - Ahmed, Kazi Matin
AU - Schlosser, Peter
AU - van Geen, Alexander
N1 - Funding Information:
Columbia University and the University of Dhaka’s research in Araihazar, Bangladesh has been supported since 2000 by NIEHS Superfund Research Program grant P42 ES010349. NSF Coupled Natural and Human Systems Dynamics grant ICER 1414131 provided additional support. We thank M. S. Shahud, M. M. Hosain, and the villagers at site M for their help in the field, L. Baker, R. Friedrich, and R. Newton for data acquisition help, and Y. Zheng, H. Michael, and C. F. Harvey for their ideas and comments. This is Lamont-Doherty Earth Observatory contribution number 8396.
Publisher Copyright:
© 2020, The Author(s).
PY - 2020/12/1
Y1 - 2020/12/1
N2 - Confining clay layers typically protect groundwater aquifers against downward intrusion of contaminants. In the context of groundwater arsenic in Bangladesh, we challenge this notion here by showing that organic carbon drawn from a clay layer into a low-arsenic pre-Holocene (>12 kyr-old) aquifer promotes the reductive dissolution of iron oxides and the release of arsenic. The finding explains a steady rise in arsenic concentrations in a pre-Holocene aquifer below such a clay layer and the repeated failure of a structurally sound community well. Tritium measurements indicate that groundwater from the affected depth interval (40–50 m) was recharged >60 years ago. Deeper (55–65 m) groundwater in the same pre-Holocene aquifer was recharged only 10–50 years ago but is still low in arsenic. Proximity to a confining clay layer that expels organic carbon as an indirect response to groundwater pumping, rather than directly accelerated recharge, caused arsenic contamination of this pre-Holocene aquifer.
AB - Confining clay layers typically protect groundwater aquifers against downward intrusion of contaminants. In the context of groundwater arsenic in Bangladesh, we challenge this notion here by showing that organic carbon drawn from a clay layer into a low-arsenic pre-Holocene (>12 kyr-old) aquifer promotes the reductive dissolution of iron oxides and the release of arsenic. The finding explains a steady rise in arsenic concentrations in a pre-Holocene aquifer below such a clay layer and the repeated failure of a structurally sound community well. Tritium measurements indicate that groundwater from the affected depth interval (40–50 m) was recharged >60 years ago. Deeper (55–65 m) groundwater in the same pre-Holocene aquifer was recharged only 10–50 years ago but is still low in arsenic. Proximity to a confining clay layer that expels organic carbon as an indirect response to groundwater pumping, rather than directly accelerated recharge, caused arsenic contamination of this pre-Holocene aquifer.
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U2 - 10.1038/s41467-020-16104-z
DO - 10.1038/s41467-020-16104-z
M3 - Article
C2 - 32382006
AN - SCOPUS:85084380278
SN - 2041-1723
VL - 11
JO - Nature communications
JF - Nature communications
IS - 1
M1 - 2244
ER -