Identifying sources and controlling factors of arsenic release in saline groundwater aquifers
An integrated hydrogeochemical study was carried out to realize the occurrence of arsenic (As) in a saline aquifer. Saline groundwater was mostly concentrated in the uppermost aquifer, and non-saline water was in the lower aquifer in the study area. High As concentrations were found in both the uppe...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2014-03-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | http://www.hydrol-earth-syst-sci.net/18/1089/2014/hess-18-1089-2014.pdf |
| _version_ | 1818288018990039040 |
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| author | C.-W. Liu K.-L. Lu Y.-H. Kao C.-J. Wang S.-K. Maji J.-F. Lee |
| author_facet | C.-W. Liu K.-L. Lu Y.-H. Kao C.-J. Wang S.-K. Maji J.-F. Lee |
| author_sort | C.-W. Liu |
| collection | DOAJ |
| description | An integrated hydrogeochemical study was carried out to realize the
occurrence of arsenic (As) in a saline aquifer. Saline groundwater was mostly
concentrated in the uppermost aquifer, and non-saline water was in the lower
aquifer in the study area. High As concentrations were found in both the
uppermost and lower aquifers. No correlation among salinity, well depth and
As concentration was observed. Various forms of Fe oxyhydroxides were
identified in the magnetic fractions, which were concentrated by high
gradient magnetic separation (HGMS) technique, revealing that the redox
cycling of Fe occurred in the subsurface. High levels of Fe, HCO<sub>3</sub><sup>-</sup>,
DOC and NH<sub>4</sub><sup>+</sup> concentrations accompanying alkaline pH in the As-rich
groundwater were consistent with the mechanism triggered by the microbially
mediated reductive dissolution of Fe oxyhydroxides. A proposed threshold
value of 50μg L<sup>-1</sup> As concentration was used as an indicator
for identification of active proceeding reductive dissolution of As-bearing
Fe oxyhydroxides in the saline aquifer. Desorption behaviors of As were
relevant to its valence in the sediments and the co-existence of anions.
Experimental and numerical results showed that additions of Cl<sup>-</sup> and
SO<sub>4</sub><sup>2-</sup>, which represent the main anions of saline water, had minor
effect on leaching sedimentary As. Although bicarbonate addition resulted in
less As desorption than that of phosphate on a molar basis, the contribution
of bicarbonate to the total release of As was greater than phosphate due to
the much higher concentration of bicarbonate in shallow groundwater and the
associated microbial mediation. Collectively, the chemical effect of saline
water on the As release to groundwater is mild in the coastal aquifer. |
| first_indexed | 2024-12-13T01:49:43Z |
| format | Article |
| id | doaj.art-4494d07524204c34821724403ca33df7 |
| institution | Directory Open Access Journal |
| issn | 1027-5606 1607-7938 |
| language | English |
| last_indexed | 2024-12-13T01:49:43Z |
| publishDate | 2014-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Hydrology and Earth System Sciences |
| spelling | doaj.art-4494d07524204c34821724403ca33df72022-12-22T00:03:32ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382014-03-011831089110310.5194/hess-18-1089-2014Identifying sources and controlling factors of arsenic release in saline groundwater aquifersC.-W. Liu0K.-L. Lu1Y.-H. Kao2C.-J. Wang3S.-K. Maji4J.-F. Lee5Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan, 10617, ROCDepartment of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan, 10617, ROCDepartment of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan, 10617, ROCDepartment of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan, 10617, ROCDepartment of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan, 10617, ROCNational Synchrotron Radiation Research Center, Hsinchu, Taiwan, 300, ROCAn integrated hydrogeochemical study was carried out to realize the occurrence of arsenic (As) in a saline aquifer. Saline groundwater was mostly concentrated in the uppermost aquifer, and non-saline water was in the lower aquifer in the study area. High As concentrations were found in both the uppermost and lower aquifers. No correlation among salinity, well depth and As concentration was observed. Various forms of Fe oxyhydroxides were identified in the magnetic fractions, which were concentrated by high gradient magnetic separation (HGMS) technique, revealing that the redox cycling of Fe occurred in the subsurface. High levels of Fe, HCO<sub>3</sub><sup>-</sup>, DOC and NH<sub>4</sub><sup>+</sup> concentrations accompanying alkaline pH in the As-rich groundwater were consistent with the mechanism triggered by the microbially mediated reductive dissolution of Fe oxyhydroxides. A proposed threshold value of 50μg L<sup>-1</sup> As concentration was used as an indicator for identification of active proceeding reductive dissolution of As-bearing Fe oxyhydroxides in the saline aquifer. Desorption behaviors of As were relevant to its valence in the sediments and the co-existence of anions. Experimental and numerical results showed that additions of Cl<sup>-</sup> and SO<sub>4</sub><sup>2-</sup>, which represent the main anions of saline water, had minor effect on leaching sedimentary As. Although bicarbonate addition resulted in less As desorption than that of phosphate on a molar basis, the contribution of bicarbonate to the total release of As was greater than phosphate due to the much higher concentration of bicarbonate in shallow groundwater and the associated microbial mediation. Collectively, the chemical effect of saline water on the As release to groundwater is mild in the coastal aquifer.http://www.hydrol-earth-syst-sci.net/18/1089/2014/hess-18-1089-2014.pdf |
| spellingShingle | C.-W. Liu K.-L. Lu Y.-H. Kao C.-J. Wang S.-K. Maji J.-F. Lee Identifying sources and controlling factors of arsenic release in saline groundwater aquifers Hydrology and Earth System Sciences |
| title | Identifying sources and controlling factors of arsenic release in saline groundwater aquifers |
| title_full | Identifying sources and controlling factors of arsenic release in saline groundwater aquifers |
| title_fullStr | Identifying sources and controlling factors of arsenic release in saline groundwater aquifers |
| title_full_unstemmed | Identifying sources and controlling factors of arsenic release in saline groundwater aquifers |
| title_short | Identifying sources and controlling factors of arsenic release in saline groundwater aquifers |
| title_sort | identifying sources and controlling factors of arsenic release in saline groundwater aquifers |
| url | http://www.hydrol-earth-syst-sci.net/18/1089/2014/hess-18-1089-2014.pdf |
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