Point Sources
This image shows a point source of industrial pollution along the Calumet River.
Pollution sources are classified by two main groups: point sources and nonpoint sources. Point sources are spatially and temporally defined, such as sewage treatment plants and operational wastes from industries. These sources are easy to identify and come from one particular location.
Nonpoint Sources
Nonpoint sources are impossible to locate or confine and is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water. These pollutants include:
Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas;
Oil, grease, and toxic chemicals from urban runoff and energy production;
Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks;
Salt from irrigation practices and acid drainage from abandoned mines;
Bacteria and nutrients from livestock, pet wastes, and faulty septicsystems;
Atmospheric deposition and hydromodification are also sources of nonpoint source pollution.
Artificial eutrophication occurs when human activity introduces increased amounts of these nutrients, which speed up plant growth and eventually choke the lake of all of its animal life.
