Groundwater dynamics and arsenic mobilization in Bangladesh assessed using noble gases and tritium

被引:113
作者
Klump, S
Kipfer, R
Cirpka, OA
Harvey, CF
Brennwald, MS
Ashfaque, KN
Badruzzaman, ABM
Hug, SJ
Imboden, DM
机构
[1] Swiss Fed Swiss Inst Aquat Sci & Technol, Dept Water Resources & Drinking Water, CH-8600 Dubendorf, Switzerland
[2] ETH, Dept Environm Sci, Swiss Fed Inst Technol, CH-8092 Zurich, Switzerland
[3] ETH, Dept Earth Sci, Swiss Fed Inst Technol, CH-8092 Zurich, Switzerland
[4] MIT, Lab Water Resources & Hydrodynam, Dept Civil & Environm Engn, Cambridge, MA 02139 USA
[5] Bangladesh Univ Engn & Technol, Dept Civil Engn, Dhaka 1000, Bangladesh
关键词
D O I
10.1021/es051284w
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
The contamination of groundwater by geogenic arsenic is the cause of major health problems in south and southeast Asia. Various hypotheses proposing that As is mobilized by the reduction of iron (oxy)hydroxides are now under discussion. One important and controversial question concerns the possibility that As contamination might be related to the extraction of groundwater for irrigation purposes. If As were mobilized by the inflow of re-infiltrating irrigation water rich in labile organic carbon, As-contaminated groundwater would have been recharged after the introduction of groundwater irrigation 20-40 years ago. We used environmental tracer data and conceptual groundwater flow and transport modeling to study the effects of groundwater pumping and to assess the role of re-infiltrated irrigation water in the mobilization of As. Both the tracer data and the model results suggest that pumping induces convergent groundwater flow to the depth of extraction and causes shallow, young groundwater to mix with deep, old groundwater. The As concentrations are greatest at a depth of 30 m where these two groundwater bodies come into contact and mix. There, within the mixing zone, groundwater age significantly exceeds 30 years, indicating that recharge of most of the contaminated water occurred before groundwater irrigation became established in Bangladesh. Hence, at least at our study site, the results call into question the validity of the hypothesis that re-infiltrated irrigation water is the direct cause of As mobilization; however, the tracer data suggest that, at our site, hydraulic changes due to groundwater extraction for irrigation might be related to the mobilization of As.
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页码:243 / 250
页数:8
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