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Title: Adsorption and desorption of phosphate on limestone in experiments simulating seawater intrusion

item PRICE, RENE - Florida International University
item Savabi, M
item JOLICOEUR, JEAN - Broward Community College
item ROY, SRIKUMAR - Swiss Federal Institute Of Technology Zurich

Submitted to: Applied Geochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2010
Publication Date: 4/24/2010
Citation: Price, R.M., Savabi, M.R., Jolicoeur, J.L., Roy, S. 2010. Adsorption and desorption of phosphate on limestone in experiments simulating seawater intrusion. Applied Geochemistry. 25:1085-1091

Interpretive Summary: Information about the water and agrochemical flow through different aquifer formation in south Florida is important during the proposed water flow change due the Everglades Restoration. In this study, we provided an estimate of how the phosphorus transfer through a large block of Key Largo Limestone from south Florida under exposure to deionized water (DIW) and seawater. The DIW experiments represented infiltration of rainwater with P, while the seawater experiments simulated seawater intrusion into the carbonate aquifer. The objectives of the study were: 1) to determine the adsorption/desorption characteristics of P on limestone in fresh water versus seawater; and 2) to identify the geochemical reactions responsible for the release of phosphorus from the limestone as a result of seawater intrusion.

Technical Abstract: The absorption and desorption of phosphorus on a large block of limestone was investigated using deionized water (DIW) and seawater. The limestone had a high affinity to adsorb phosphorus in DIW. Phosphate adsorption was significantly less in seawater, and more phosphorus was desorbed in the seawater compared to the DIW. Dissolution of carbonate minerals, calcite and aragonite were found to release phosphorus at low salinities. At higher salinities, ion exchange reactions involving bicarbonate most likely desorbed phosphorus. The results of this study suggest that as seawater intrudes into a fresh coastal aquifer, phosphorus would be expected to be released into the groundwater.