Recharge of low-arsenic aquifers tapped by community wells in Araihazar, Bangladesh, inferred from environmental isotopes

I. Mihajlov, M. Stute, P. Schlosser, B. J. Mailloux, Y. Zheng, I. Choudhury, K. M. Ahmed, A. van Geen

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

More than 100,000 community wells have been installed in the 150–300 m depth range throughout Bangladesh over the past decade to provide low-arsenic drinking water (<10 µg/L As), but little is known about how aquifers tapped by these wells are recharged. Within a 25 km2 area of Bangladesh east of Dhaka, groundwater from 65 low-As wells in the 35–240 m depth range was sampled for tritium (3H), oxygen and hydrogen isotopes of water (18O/16O and 2H/1H), carbon isotope ratios in dissolved inorganic carbon (DIC, 14C/12C and 13C/12C), noble gases, and a suite of dissolved constituents, including major cations, anions, and trace elements. At shallow depths (<90 m), 24 out of 42 wells contain detectable 3H of up to 6 TU, indicating the presence of groundwater recharged within 60 years. Radiocarbon (14C) ages in DIC range from modern to 10 kyr. In the 90–240 m depth range, however, only five wells shallower than 150 m contain detectable 3H (<0.3 TU) and 14C ages of DIC cluster around 10 kyr. The radiogenic helium (4He) content in groundwater increases linearly across the entire range of 14C ages at a rate of 2.5 × 10−12 ccSTP 4He g−1 yr−1. Within the samples from depths >90 m, systematic relationships between 18O/16O, 2H/1H, 13C/12C, and 14C/12C, and variations in noble gas temperatures, suggest that changes in monsoon intensity and vegetation cover occurred at the onset of the Holocene, when the sampled water was recharged. Thus, the deeper low-As aquifers remain relatively isolated from the shallow, high-As aquifer.

Original languageEnglish (US)
Pages (from-to)3324-3349
Number of pages26
JournalWater Resources Research
Volume52
Issue number5
DOIs
StatePublished - May 1 2016

Keywords

  • Bangladesh
  • arsenic
  • groundwater dating
  • noble gas temperatures
  • radiocarbon
  • tritium

ASJC Scopus subject areas

  • Water Science and Technology

Fingerprint Dive into the research topics of 'Recharge of low-arsenic aquifers tapped by community wells in Araihazar, Bangladesh, inferred from environmental isotopes'. Together they form a unique fingerprint.

  • Cite this