Causes of pollution of freshwater and sea water
Answers
Classification of water pollution depends on the criterion used for categorization of pollution. Based on the medium in which pollutants occur, types of water pollution may be distinguished as fresh water pollution and marine pollution. Fresh water pollution can be categorized into pollution of surface water and pollution of ground-water. When the pollutant enters a lake, pond, or river it is known as surface water pollution. If, however, the pollutant finds its way into aquifer, along with water of percolation, it deteriorates the quality of groundwater, and is called groundwater pollution.
You have noticed that groundwater bodies and surface water bodies together have been kept under the class fresh water bodies because their salt content is very low; always less than 5 ppt (parts per thousand). As against this, the water bodies containing salt concentration equal to or above that of sea water (i.e., 35 ppt or above) are called as marine water bodies. Estuaries and brackish waters have salt content somewhere in between 5 to 35 ppt. The pollution of oceans, seas, estuaries, salt marshes and other similar water bodies is known as marine pollution or ocean pollution. We will discuss this separately because the factors polluting oceans acquire different dimensions ensuing from the magnitude of water bodies involved.