TY - JOUR T1 - Aquifer-Scale Observations of Iron Redox Transformations in Arsenic-Impacted Environments to Predict Future Contamination JF - Environmental Science & Technology Letters Y1 - 2020 A1 - Nghiem, Athena A. A1 - Shen, Yating A1 - Stahl, Mason A1 - Sun, Jing A1 - Haque, Ezazul A1 - DeYoung, Beck A1 - Nguyen, Khue N. A1 - Thi Mai, Tran A1 - Trang, Pham Thi Kim A1 - Pham, Hung Viet A1 - Mailloux, Brian A1 - Harvey, Charles F. A1 - van Geen, Alexander A1 - Bostick, Benjamín C. KW - BANGLADESH KW - BENGAL BASIN KW - groundwater KW - PLEISTOCENE AQUIFER KW - POLLUTION KW - RELEASE KW - RIVER DELTA KW - Sediment KW - TRANSPORT KW - VIETNAM AB - 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. VL - 7 UR - 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- IS - 12 ER - TY - JOUR T1 - Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance JF - Nature Communications Y1 - 2018 A1 - Hodgkins, Suzanne B. A1 - Richardson, Curtis J. A1 - Dommain, René A1 - Wang, Hongjun A1 - Glaser, Paul H. A1 - Verbeke, Brittany A1 - Winkler, B. Rose A1 - Cobb, Alexander R. A1 - Rich, Virginia I. A1 - Missilmani, Malak A1 - Flanagan, Neal A1 - Ho, Mengchi A1 - Hoyt, Alison M. A1 - Harvey, Charles F. A1 - Vining, S. Rose A1 - Hough, Moira A. A1 - Moore, Tim R. A1 - Richard, Pierre J. H. A1 - De La Cruz, Florentino B. A1 - Toufaily, Joumana A1 - Hamdan, Rasha A1 - Cooper, William T. A1 - Chanton, Jeffrey P. AB - Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats. VL - 9 UR - http://www.nature.com/articles/s41467-018-06050-2 IS - 1 ER -