@article {2919,
	title = {Aquifer-Scale Observations of Iron Redox Transformations in Arsenic-Impacted Environments to Predict Future Contamination},
	journal = {Environmental Science \& Technology Letters},
	volume = {7},
	year = {2020},
	month = {Aug-12-2020},
	pages = {916 - 922},
	abstract = {Iron oxides control the mobility of a host of contaminants in aquifer systems, and the microbial reduction of iron oxides in the subsurface is linked to high levels of arsenic in groundwater that affects greater than 150 million people globally. Paired observations of groundwater and solid-phase aquifer composition are critical to understand spatial and temporal trends in contamination and effectively manage changing water resources, yet field-representative mineralogical data are sparse across redox gradients relevant to arsenic contamination. We characterize iron mineralogy using X-ray absorption spectroscopy across a natural gradient of groundwater arsenic contamination in Vietnam. Hierarchical cluster analysis classifies sediments into meaningful groups delineating weathering and redox changes, diagnostic of depositional history, in this first direct characterization of redox transformations in the field. Notably, these groupings reveal a signature of iron minerals undergoing active reduction before the onset of arsenic contamination in groundwater. Pleistocene sediments undergoing postdepositional reduction may be more extensive than previously recognized due to previous misclassification. By upscaling to similar environments in South and Southeast Asia via multinomial logistic regression modeling, we show that active iron reduction, and therefore susceptibility to future arsenic contamination, is more widely distributed in presumably pristine aquifers than anticipated.},
	keywords = {BANGLADESH, BENGAL BASIN, groundwater, PLEISTOCENE AQUIFER, POLLUTION, RELEASE, RIVER DELTA, Sediment, TRANSPORT, VIETNAM},
	issn = {2328-8930},
	doi = {10.1021/acs.estlett.0c0067210.1021/acs.estlett.0c00672.s00110.1021/acs.estlett.0c00672.s00210.1021/acs.estlett.0c00672.s00310.1021/acs.estlett.0c00672.s004},
	url = {https://apps.webofknowledge.com/InboundService.do?product=WOS\&Func=Frame\&DestFail=http\%3A\%2F\%2Fwww.webofknowledge.com\&SrcApp=search\&SrcAuth=Alerting\&SID=8AkJOJLKFU3j5nkGaRI\&customersID=Alerting\&mode=FullRecord\&IsProductCode=Yes\&AlertId=4d48b20a-7d27-4fa2-},
	author = {Nghiem, Athena A. and Shen, Yating and Stahl, Mason and Sun, Jing and Haque, Ezazul and DeYoung, Beck and Nguyen, Khue N. and Thi Mai, Tran and Trang, Pham Thi Kim and Pham, Hung Viet and Mailloux, Brian and Harvey, Charles F. and van Geen, Alexander and Bostick, Benjam{\'\i}n C.}
}
@article {2704,
	title = {Arsenic contamination of Bangladesh aquifers exacerbated by clay layers},
	journal = {Nature Communications},
	volume = {11},
	year = {2020},
	month = {Jan-12-2020},
	abstract = {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{\textendash}50 m) was recharged >60 years ago. Deeper (55{\textendash}65 m) groundwater in the same pre-Holocene aquifer was recharged only 10{\textendash}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.},
	doi = {10.1038/s41467-020-16104-z},
	url = {https://www.nature.com/articles/s41467-020-16104-z},
	author = {Mihajlov, Ivan and Mozumder, M. Rajib H. and Bostick, Benjam{\'\i}n C. and Stute, Martin and Mailloux, Brian J. and Knappett, Peter S. K. and Choudhury, Imtiaz and Ahmed, Kazi Matin and Schlosser, Peter and van Geen, Alexander}
}
