Environmental Contaminant Source and Transport Pathways Illustration

Illustration showing examples of environmental contaminant source and transport pathways. This illustration is a higher resolution version of figure 4 of USGS Circular 1383-E and figure 1 of USGS Open-file Report 2015-1113.

Modern human societies produce large amounts of a diverse array of chemicals and other substances that are used in manufacturing, agriculture, medical treatment, transportation, construction, and other applications. There are many pathways by which contaminants can enter the environment. Some of these substances, such as fertilizers and pesticides, are intentionally released into the environment and can become problematic if improperly used or handled. Other chemicals or substances are released into the environment as byproducts of human activities and can be problematic, such as wastes from fossil fuel combustion, and numerous chemicals found in household products associated with treated wastewaters (for example detergents, fire retardants, and pharmaceuticals). Additional contaminants, such as metals, minerals, petroleum products, solvents, and other commercial or industrial substances, are not intended for release but nevertheless find their way into the environment because of unintended, accidental, or malicious releases. Finally, naturally occurring earth processes such as volcanic eruptions, earthquakes, erosion by wind and water, and chemical weathering of rocks also deliver mineral, chemical, and radionuclide contamination to the environment.