Hydrochemical Impacts of Limestone Rock Mining
2011
Naja, Ghinwa M. | Rivero, Rosanna | Davis, Stephen E. III | Van Lent, Thomas
Hydrochemical impacts of shallow rock industrial-scale mining activities close to sensitive constructed and natural wetlands were investigated. The shallow surficial groundwater and surface water in the Everglades Agricultural Area (EAA) were characterized. The chemical composition of sulfate and chloride in groundwater increased with depth. The average concentration of chloride averaged 182Â mgâL−1 at 6Â m deep and increased gradually to 1,010Â mgâL−1 at 15Â m deep, 1,550Â mgâL−1 at 30Â m deep to reach 7,800Â mgâL−1 at 60Â m deep. Comparatively, the surface water chemical composition in the surrounding areas showed much lower cationic and anionic charge. The specific conductivity and total dissolved solids of surface water in canals (close to the mining operations) are <900Â μSâcm−1 and <600Â mgâL−1, respectively, which should be compared to groundwater quality in wells from the EAA area (>2,000Â μSâcm−1 and >1,000Â mgâL−1, respectively). A steady-state groundwater fluid flow and transient solute transport modeling exercise was conducted to estimate surface/groundwater interactions. The modeled solute in surface water was transported downgradient through groundwaters, migrated approximately 30Â m from the source area (after 5Â years of operation), and needed more than 116Â years to dissipate. An upward transport was also identified whereby chloride and sulfate, naturally present in deeper groundwaters, migrated approximately 200Â m (after 1Â year of mining) into the pristine shallower aquifer and reached the surface water with a concentration equaling 80% of that in the rock mining pit.
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