Document Detail


Groundwater geochemistry and its implications for arsenic mobilization in shallow aquifers of the Hetao Basin, Inner Mongolia.
MedLine Citation:
PMID:  18234287     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Arsenic concentrations in shallow groundwaters from the Hetao Basin of Inner Mongolia range between 0.6 and 572 microg/L. High As groundwaters generally occur in the shallow alluvial-lacustrine aquifers, which are mainly composed of black (or dark grey) fine sands in a reducing environment. They are characterized by high concentrations of dissolved Fe, Mn, HCO(3)(-), P and S(2-), and low concentrations of NO(3)(-) and SO(4)(2-). Low SO(4)(2-) coupled with high S(2-) suggests that SO(4)(2-) reduction has been an active process. In the reducing groundwaters, inorganic As(III) accounts for around 75% of total dissolved As. Total As contents in the sediments from three representative boreholes are observed to be 7.3-73.3 mg/kg (average of 18.9 mg/kg). The total As is mildly-strongly correlated with total Fe and total Mn, while a quite weak correlation exists between total As and total S, suggesting that the As is associated with Fe-Mn oxides, rather than sulfides in the sediments. It is found in the sequential extraction that chemically active As is mainly bound to Fe-Mn oxides, up to 3500 microg/kg. The mobilization of As under reducing conditions is believed to include reductive dissolution of Fe-Mn oxides and reduction of adsorbed As. Although exchangeable As is labile and very vulnerable to hydrogeochemical condition, the contribution is relatively limited due to the low concentrations. The competition between As and other anions (such as HPO(4)(2-)) for binding sites on Fe-Mn oxides may also give rise to the release of As into groundwater. Slow groundwater movement helps accumulation of the released As in the groundwaters.
Authors:
Huaming Guo; Suzhen Yang; Xiaohui Tang; Yuan Li; Zhaoli Shen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-01-30
Journal Detail:
Title:  The Science of the total environment     Volume:  393     ISSN:  0048-9697     ISO Abbreviation:  Sci. Total Environ.     Publication Date:  2008 Apr 
Date Detail:
Created Date:  2008-02-18     Completed Date:  2008-06-10     Revised Date:  2008-07-15    
Medline Journal Info:
Nlm Unique ID:  0330500     Medline TA:  Sci Total Environ     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  131-44     Citation Subset:  IM    
Affiliation:
School of Water Resources and Environment, China University of Geosciences, Beijing 100083, People's Republic of China. hmguo@cugb.edu.cn
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MeSH Terms
Descriptor/Qualifier:
Arsenic / analysis*
Bicarbonates / analysis
China
Chlorides / analysis
Environmental Monitoring
Fluorine / analysis
Geologic Sediments / analysis
Metals / analysis
Nitrates / analysis
Oxides / analysis
Phosphorus / analysis
Sulfates / analysis
Sulfur / analysis
Water Pollutants, Chemical / analysis*
Water Supply / analysis*
Chemical
Reg. No./Substance:
0/Bicarbonates; 0/Chlorides; 0/Metals; 0/Nitrates; 0/Oxides; 0/Sulfates; 0/Water Pollutants, Chemical; 7440-38-2/Arsenic; 7704-34-9/Sulfur; 7723-14-0/Phosphorus; 7782-41-4/Fluorine

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