『Abstract
This study investigates the potential release of PO43-
from carbonate aquifers exposed to seawater intrusion. Adsorption
and desorption of PO43- in the
presence of deionized water (DIW) and seawater were conducted
on a large block of Pleistocene age limestone to simulate the
effects of seawater intrusion into a coastal carbonate aquifer
at the laboratory scale. The limestone showed strong adsorption
of PO43- in DIW, while adsorption
was significantly less in the presence of seawater. Dissolution
of CaCO3 was found to prevent PO43-
adsorption at salinities less than 30 psu. Adsorption of PO43- was limited at higher salinities
(30-33 psu), due to competition with HCO3-
ions for adsorption sites. At a salinity ＜33, some PO43-
adsorption occurred as CaCO3 precipitated.
Concentrations of PO43- between
2 and 5 μmol/L were released by desorption when the limestone
was exposed to seawater. The results of this study suggest that
as seawater intrudes into an originally freshwater coastal aquifer,
adsorbed PO43- may be released
into the groundwater. Consequently, adsorbed PO43-
is expected to be released from coastal carbonate aquifers world-wide
as sea level continues to rise exposing more of the freshwater
aquifer to seawater.』
1. Introduction
2. Methods and materials
3. Results
3.1. Adsorption of phosphate in DIW
3.2. Adsorption of phosphate in seawater
3.3. Desorption of phosphate in DIW and seawater
3.4. Geochemical analysis
4. Discussion
4.1. Adsorption/desorption of phosphate in DIW
4.2. Phosphate adsorption/desorption during seawater intrusion
Acknowledgments
References