Verifying The Use Of Specific Conductance As A Surrogate For Chloride In Seawater Matrices

Coastal groundwater supplies, when overused, are particularly vulnerable to chloride contamination due to their close proximity to saltwater. Elevated chloride concentration in groundwater is the most commonly used indicator of saltwater intrusion in coastal aquifers. Rather well-defined relationships of specific conductance (SC) to chloride exist (Hem 1992; Christensenetal. 1999). To validate the relationship between SC and chloride, SC measurements by electrochemical conductivity cells and chloride concentration measurements by ion-selective electrode (ISE) were determined for 35 PSU OSIL Atlantic Seawater Standard and 10 dilutions at six different temperatures (66 unique samples). Seawater has an average chloride concentration of 19,000 mg/L (Hem 1992). A strong linear relationship was established, thus demonstrating the validity of using SC as a surrogate for chloride estimation. This study also compared inherent measurement drift of a chloride ISE and a conductivity sensor under controlled laboratory conditions over a seven-day period. Minimal drift of the conductivity sensor coupled with a large drift of the chloride ISE demonstrates a significant advantage of the conductivity sensor for longterm field deployments.

Coastal groundwater supplies, when overused, are particularly vulnerable to chloride contamination due to their close proximity to saltwater. Elevated chloride concentration in groundwater is the most commonly used indicator of saltwater intrusion in coastal aquifers. Saltwater intrusion decreases freshwater levels in an aquifer and can lead to abandonment of supply wells. Some prominent areas facing saltwater intrusion include the Mediterranean, the Yucatan Peninsula in Mexico, the Middle East, California, and the Atlantic Coast of the United States, especially in densely populated areas.