@article {Radloff2017142,
	title = {Reversible adsorption and flushing of arsenic in a shallow, Holocene aquifer of Bangladesh},
	journal = {Applied Geochemistry},
	volume = {77},
	year = {2017},
	note = {Environmental and Health Roles of Geogenic Arsenic},
	pages = {142 - 157},
	abstract = {Abstract The spatial heterogeneity of dissolved arsenic (As) concentrations in shallow groundwater of the Bengal Basin has been attributed to transport of As (and reactive carbon) from external sources or to the release of As from within grey sand formations. We explore the latter scenario in this detailed hydrological and geochemical study along a 300~m transect of a shallow aquifer extending from a groundwater recharge area within a sandy channel bar to its discharge into a nearby stream. Within the 10{\textendash}20~m depth range, groundwater ages along the transect determined by the 3H{\textendash}3He method increase from \&lt;10~yr in the recharge area to a maximum of 40~yr towards the stream. Concentrations of groundwater As within the same grey sands increase from 10 to 100 to \~{}500~μg/L along this transect. Evidence of reversible adsorption of As between the groundwater and sediment was obtained from a series of push{\textendash}pull experiments, traditional batch adsorption experiments, and the accidental flooding of a shallow monitoring well. Assuming reversible adsorption and a distribution coefficient, Kd, of 0.15{\textendash}1.5~L/kg inferred from these observations, a simple flushing model shows that the increase in As concentrations with depth and groundwater age at this site, and at other sites in the Bengal and Red River Basins, can be attributed to the evolution of the aquifer over 100{\textendash}1000 years as aquifer sands are gradually flushed of their initial As content. A wide range of As concentrations can thus be maintained in groundwater with increases with depth governed by the history of flushing and local recharge rates, without external inputs of reactive carbon or As from other sources.},
	keywords = {Push{\textendash}pull tests},
	issn = {0883-2927},
	doi = {http://doi.org/10.1016/j.apgeochem.2015.11.003},
	url = {http://www.sciencedirect.com/science/article/pii/S0883292715300706},
	author = {Kathleen A. Radloff and Yan Zheng and Martin Stute and Beth Weinman and Benjamin Bostick and Ivan Mihajlov and Margaret Bounds and M.Moshiur Rahman and M.Rezaul Huq and Kazi M. Ahmed and Peter Schlosser and Alexander van Geen}
}
