Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
581153 | Journal of Hazardous Materials | 2009 | 7 Pages |
Abstract
Fluoride concentrations in groundwater near Nagar Parkar in the Thar Desert of southeastern Pakistan range from 1.13 to 7.85Â mg/l, and roughly 78% of the samples contain fluoride in concentrations that exceed the drinking water standard of 1.5Â mg/l set by WHO. The groundwater is alkaline (pH 7.1-8.4), brackish (TDS 449-15,933Â mg/l), and classified as Na-Cl type water. This prevailing chemical character reflects the influence of saltwater intrusion, high evaporation rates, and ion exchange. Groundwater is also supersaturated with respect to calcite, which promotes the removal of Ca2+ and HCO3â from solution. As a result, groundwater is generally undersaturated with respect to fluorite, the mineral that typically controls the upper limit of fluoride concentrations. This study examines a number of geochemical parameters in an effort to discover the controls on fluoride concentrations in groundwater. High fluoride concentrations are associated with high TDS, high pH, high Na concentrations, and high sodium absorption ratios (SAR). This suggests that elevated fluoride levels are the result of enhanced fluorite solubility due to Ca depletion and high ionic strength and the release of fluoride from colloid surfaces under high pH conditions. Contrary to what has been found in other studies, sample depth and water temperature do not appear to have a significant role in the distribution of fluoride within the groundwater.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Health and Safety
Authors
Tahir Rafique, Shahid Naseem, Tanzil Haider Usmani, Erum Bashir, Farooque Ahmed Khan, Muhammad Iqbal Bhanger,