8.1 - Sources of Pollution

Learning Objectives

I. Defining Pollutants vs. Pollution

• In APES, you should intentionally use the word pollutants rather than the vague word “pollution.”

• Pollutants are specific chemicals or groups of chemicals that come from specific sources and have specific human and environmental health consequences. Using specific pollutants is much more likely to earn FRQ credit.

• Pollution is a vague, non-descript idea referring to any substance that’s unwanted in the environment. Using the word “pollution” by itself will almost never earn credit on an FRQ.

• However, mentioning a specific category of pollution, like thermal pollution, noise pollution, or sediment pollution, may be acceptable, because those are more detailed.

II. Point Sources

• Definition: Sources of pollutants that can be easily identified, or easily pointed to. Pollutants enter the environment from an easily identified and confined place.

• Examples of sources and pollutants:
• Discharge pipe: A pipe from a farm or CAFO (Concentrated Animal Feeding Operation). The waste contains pollutants like ammonia, a nitrogen source that leads to eutrophication, and fecal coliform bacteria, which are harmful to humans.
• Coal fired power plants: Release specific air pollutants from a single, identifiable location, including particulate matter, carbon dioxide, NOx, and SOx.
• Oil spills: An event like the BP oil spill is a point source, because we know exactly where it came from. It releases hydrocarbons and benzene.

III. Non-Point Sources

• Definition: Sources that can’t be pointed to easily. Pollutants enter the environment from many places at once, which makes it really difficult to identify the individual source.

• Examples of sources and pollutants:
• Urban runoff: Stormwater runoff over a large urban area collects pollutants on the pavement and flows into storm drains. Because the water comes from a huge area, it’s considered a non-point source. Specific pollutants include motor oil, nitrate from fertilizers, road salts, and sediment.
• Pesticide application: Pesticides like atrazine or glyphosate are sprayed and dispersed over large agricultural areas by wind or runoff. It’s hard to pinpoint where the pollutants came from if they show up in a river.
• Estuaries and bays: These environments receive non-point source pollution from many watersheds and organizations, which makes it difficult to assign responsibility, similar to a Tragedy of the Commons.

• Why the difference matters: Point sources are easier to monitor and regulate, because you can test the water or air right where it leaves the pipe or smokestack and hold that one facility responsible. In the US, the Clean Water Act requires a permit for every point source that discharges pollutants into lakes, rivers, and streams. Nonpoint sources are much harder to control, so the solutions are land management practices spread across a whole watershed, like riparian buffers, cover crops, and permeable pavement (see 5.13 and 8.4).

Big picture: The critical distinction in environmental science is between point sources, where pollutants like SOx and particulate matter can be traced to a single exit such as a coal power plant or a discharge pipe, and non-point sources, where pollutants like motor oil and nitrate come from vast areas such as urban runoff or widespread pesticide use. Always name specific pollutants rather than vaguely referring to “pollution.”