期刊
JOURNAL OF HYDROLOGY
卷 525, 期 -, 页码 302-312出版社
ELSEVIER
DOI: 10.1016/j.jhydrol.2015.03.017
关键词
Crystalline aquifer; Fluoride; Hard-rock; Hydrochemical logging; India
资金
- French National Research Agency (ANR) through the VMC program (MOHINI Project) [ANR-07-VULN-08]
- French Ministry of Foreign Affairs
- French Embassy in India
Hydrochemical borehole-loggings with a submersible Idronaut Ocean Seven 302 multiparameter probe equipped of F- and NO3-ion-selective electrodes in combination with EC, pH and dissolved oxygen, were applied for characterizing fluoride (F) contamination in a crystalline (hard-rock) aquifer of a small Indian agricultural watershed where groundwater is intensively abstracted for rice irrigation. A high accuracy of F concentrations determined in-situ shown by comparing with laboratory analyses was obtained through using conductivity logs for ionic strength consideration. Large variations in chemical composition and particularly of F-concentration were observed inside boreholes, though restricted to the weathered/fractured layer down to 30-35 m depth. This conforms to the hydrogeological model of a crystalline aquifer where most groundwater flow occurs in the shallow part of the fractured zone. The general trend of increasing F content with depth results from F accumulation through water-rock interaction, but the shape of the F profile depends on the connectivity of the fracture network close to the borehole. The concentrations seen within the water-table fluctuation zone locally suggest F input from fertilizers in groundwater, in addition to the earlier-demonstrated role of evaporation from irrigation return flow. It is also likely that, locally, the deepening of boreholes has contributed to increasing the population's vulnerability by tapping F-enriched groundwater at depth. (C) 2015 Elsevier B.V. All rights reserved.
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