Geological Society of America

T192 Arsenic: From Nature to Human I

Wednesday, 31 October 2007
8:00 AM - 12:00 PM

HIGH ARSENIC IN ALLUVIAL AQUIFERS IN VARIED CLIMATIC REGIME: HYDROGEOCHEMICAL COMPARISON BETWEEN HUHHOT BASIN, INNER MONGOLIA, PR CHINA AND BENGAL BASIN, INDIA AND BANGLADESH

Paper number: T192-12
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Prosun Bhattacharya Presenting Author
KTH Royal Institute of Technology, Stockholm
Abhijit Mukherjee
University of Texas at Austin, Austin, TX
Fei Shi
Royal Institute of Technology (KTH), Stockholm, N/A
Zheng Miao Xie
Hangzhou Dianzi University, Hangzhou, N/A
Arun B. Mukherjee
University of Helsinki, University of Helsinki, N/A
Ondra Sracek
Masaryk University, Brno, N/A
Yongguan Zhu
Chinese Academy of Sciences, Beijing, N/A
Jochen Bundschuh
National Cheng Kung University, Tainan City
Gunnar Jacks
KTH Royal Institute of Technology, Stockholm

Abstract

Presence of elevated arsenic (As) in the alluvial aquifers of the Ganges-Brahmaputra-Meghna river basin (Bengal basin) and Yellow river basin (Huhhot basin) are well known for about last two decades. The geogenic contamination in both the areas has been largely attributed to the hydrodynamics, including the recharge pattern and hydrochemical cycling. However, while the Bengal basin (BB) is located at low latitude, humid climate (annual mean 1400 mm precipitation) condition, Huhhot basin (HB) is located at the mid latitudes, arid to semi-arid environment (400 mm), indicating a basic difference in the recharge and hence the pattern in hydrological and geochemical cycles. Moreover, BB is comprised of fluio-detlaic deposits derived from Himalayas and the Indian craton in contrast to the Da-Quing Mountain derived fluvio-lacustrine sediments of HB. But interestingly, most of the numerous studies undertaken in BB and limited number of studies done in HB all suggests that microbially catalyzed reductive dissolution of metal oxides and hydroxides present in the organic matter affluent Holocene sediments possibly leads to the mobilization of the As.

The present study tries to understand the nuances of As mobilization in similar redox conditions under a different climatic regime and geologic setting. While BB shows prolific recharge from meteoric and non-meteoric sources, HB probably has a limited recharged, closed inland basin. Arsenic concentrations [mostly As(III)] are higher in the shallow depths of both the dominantly Ca-HCO₃- type groundwater of BB and Na-HCO₃-Cl water of HB, although the relative percentage of contaminated deeper wells is much higher than in the HB than BB. The maximum concentrations of Fe, Mn, and As are much lower in HB in contrast to BB, which shows a better correlations between As and other redox sensitive related solutes (e.g. Fe, Mn, HCO₃), probably indicating a difference in desorption mechanism and metal cycling. This is further suggested by the difference in depth-wise distribution of the solutes in the two regions. Future comparative studies are expected to illustrate the differences between the two locations in greater details with enumeration of the cause for similar mobilization mechanisms.