Category:Level 2 - Pollutants/Chloride

Category:Level 2 - Pollutants/Chloride

Effect of chloride on roadside trees. (Reprinted with permission from Bill Cook, Michigan State University Extension)

This page provides links to pages that provide information on chloride, on deicing, road salt, and other pages providing information related to these topics.

Chloride concentrations in stormwater runoff are highly variable, with very high concentrations in mid- to late-winter and early spring. The high concentrations are typically associated with salts used in road surface deicing agents and often exceed surface water and groundwater quality standards. Concentrations are much lower in summer but still elevated above natural background concentrations. Potential sources include runoff from soil, vegetative debris, automobile fluids, and animal wastes. Chloride is highly mobile in soil and will readily leach through the vadose zone and into groundwater.

At elevated concentrations, chloride can become toxic to aquatic life. Elevated levels of chloride can also result in low oxygen conditions, leading to the release of phosphorous and metals sorbed to the solids (Novotny et al., 2008). In addition, high levels of chloride will increase the density of the water, causing the salt containing water to settle to the bottom of the water body. This results in stratification and disrupts lake mixing patterns (New Hampshire Department of Environmental Services).