Hydrology of Clay Settling Areas and Surrounding Landscapes in the Phosphate Mining District, Peninsular Florida

• Published in: Journal of the American Water Resources Association Vol. 44; no. 4; pp. 980 - 995
• Main Authors: Murphy, Kathryn E, Rains, Mark C, Kittridge, Michael G, Stewart, Mark T, Ross, Mark A
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.08.2008; American Water Resources Association
• Subjects: bromides; clay; clay settling areas; clay soils; drainage; Earth sciences; Earth, ocean, space; environmental impacts; Exact sciences and technology; Freshwater; Geochemistry; ground-water hydrology; groundwater flow; Hydrogeology; hydrologic models; hydrological connectivity; Hydrology. Hydrogeology; infiltration; infiltration (hydrology); labeling techniques; landscapes; Mineralogy; mining; phosphates; preferential flow; runoff; Silicates; soil pore system; surface water; Water geochemistry; Water resources; Florida; Polk County Florida; United States; USA, Florida, Polk Cty; USA, Florida; fissures; mass balance; mixing; ground water; evapotranspiration; North America; surficial aquifers; clay; environment impact; discharge; clastic rocks; hydrological connectivity; stable isotopes; models; solutes; bromides; tracers; runoff; environmental impacts; mining; transport; halides; infiltration; desiccation; surface water; sedimentary rocks; preferential flow; mines; phosphates; water resource management; clay settling areas; ground-water hydrology
• ISSN: 1093-474X; 1752-1688
• DOI: 10.1111/j.1752-1688.2008.00211.x

The objective of this study was to use applied and naturally occurring geochemical tracers to study the hydrology of clay settling areas (CSAs) and the hydrological connectivity between CSAs and surrounding hydrological landscapes. The study site is located on the Fort Meade Mine in Polk County, Florida. The CSA has a well-developed, subangular-blocky, clay-rich surface layer with abundant desiccation cracks and other macropores, and a massive, clay-rich sublayer that is saturated below approximately 1.0-2.5 m. A bromide tracer was applied to study hydrological processes in the upper part of the CSA. Bromide infiltrated rapidly and perched on a massive, clay-rich sublayer. Bromide concentrations decreased in the upper part of the profile without being transported vertically down through the lower part of the profile suggesting that bromide was lost to lateral rather than to vertical transport. Infiltration and lateral flow were rapid suggesting that preferential flow through desiccation cracks and other macropores likely dominates flow in the upper part of the CSA. Naturally occurring solute and stable isotope tracers were used to study the hydrological connectivity between the CSA and the surrounding hydrological landscape. Three-end mass-balance mixing model results indicate that shallow and/or deep CSA water can be found in all downgradient waters and must be as much as ~50% of some downgradient waters. Discharge from the CSA to the surrounding surface water-bodies and surficial aquifer occurs laterally through the berms and/or vertically through the massive, clay-rich sublayer. However, the precise flow paths from the CSA to the surrounding hydrological landscape are unclear and the fluxes remain unquantified, so the precise effects of CSAs on the hydrology of the surrounding hydrological landscape also remain unquantified.