Salt and the environment
Chlorides are released naturally into the environment through the weathering of chloride-containing rocks and minerals. The seas and oceans contain vast amounts of dissolved chloride. Chloride also enters the atmosphere naturally as a result of volcanic activity, forest fires and sea spray. Coal also contains significant amounts of chlorine that is released into the atmosphere as hydrogen chloride during combustion, where it contributes to acid rain. Coal combustion for power generation is one of the biggest industrial sources of chloride release to the atmosphere. However this is falling as a result of the declining use of coal for power generation and the installation of emission control equipment at major power stations. Other sources of chloride release into the environment are agricultural runoff; wastewater from various food and chemical industries; consumer water softening; pool salts; effluent wastewater from water treatment facilities and; road deicing operations.