Chloride and Salinity

Introduction

Chloride, in the form of the Cl^– ion, is one of the major inorganic anions, or negative ions, in saltwater and freshwater. It originates from the dissociation of salts, such as sodium chloride or calcium chloride, in water.

These salts, and their resulting chloride ions, originate from natural minerals, saltwater intrusion into estuaries, and industrial pollution.

There are many possible sources of manmade salts that may contribute to elevated chloride readings. Sodium chloride and calcium chloride, used to salt roads, contribute to elevated chloride levels in streams. Chlorinated drinking water and sodium-chloride water softeners often increase chloride levels in wastewater of a community.

In drinking water, the salty taste produced by chloride depends upon the concentration of the chloride ion. Water containing 250 mg/L of chloride may have a detectable salty taste if the chloride came from sodium chloride. The recommended maximum level of chloride in U.S. drinking water is 250 mg/L.

Objectives

• Measure the chloride ion concentration in a stream or lake using a Chloride Ion-Selective Electrode.
• Measure the salinity value of the water (in ppt) using a Conductivity Probe.