Hydrogeochemical Analysis of Processes Through Modeling of Seawater Intrusion Impacts in Biscayne Aquifer Water Quality, USA

• Published in: Aquatic geochemistry Vol. 22; no. 3; pp. 197 - 209
• Main Authors: Habtemichael, Yonas T., Fuentes, Hector R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.06.2016; Springer Nature B.V
• Subjects: Aquifer management; Aquifers; Calcite; Cation exchange; Chemical analysis; Chemical precipitation; Coastal aquifers; Dolomite; Earth and Environmental Science; Earth Sciences; Geochemistry; Gypsum; Hydrogeology; Hydrology; Hydrology/Water Resources; Marine; Original Article; Saline water intrusion; Saturation index; Seawater; Water analysis; Water quality; Water Quality/Water Pollution; Water sampling; USA, Florida, Biscayne Aquifer; USA; USA; Geochemical modeling; Saltwater intrusion; Carbonate aquifer; Water–rock interactions
• ISSN: 1380-6165; 1573-1421
• DOI: 10.1007/s10498-016-9287-1

Hydrogeochemical processes that accompany seawater intrusion in coastal aquifers can alter the resulting water quality and are important ingredients in coastal aquifer management. The presence of dissolution–precipitation reactions and ion exchange in the mixing zone of the Biscayne aquifer (FL, USA) are suggested based on changes in major ion concentrations and mineral saturation indices (SI). Major ion concentrations from 11 groundwater samples are compared with theoretical mixing between freshwater and seawater. PHREEQC code was used to calculate saturation indices of the samples with respect to common phases in the Biscayne aquifer. High Ca 2+ and HCO 3 − content of the samples is typical of waters in contact with carbonate aquifers. Water quality of the samples is mainly attributed to mixing and precipitation–dissolution reactions with calcite and dolomite. The samples were saturated with calcite (SI ~ 0) and undersaturated for dolomite (SI < 0), while a few samples showed dolomite saturation. Because gypsum and halite SI could be predicted by theoretical mixing, reactions with those minerals, if present, are thought to be insignificant. In the active intrusion areas, cation exchange also appears to modify water quality leading to excess Ca 2+ , but depleted Na + , Mg 2+ and K + concentrations. On the other hand, samples from previous intrusion areas plotted very close to the theoretical mixing line and approached equilibrium with the seawater.