Air Pollution

Randy Mosier from the Maryland Department of the Environment explains how our watershed is affected by the “airshed” that surrounds it, and how airborne pollutants fall onto our land and into our water. (Will Parson/Chesapeake Bay Program)

FAQ

What is an airshed?

An airshed is an area of land over which airborne pollutants can travel to enter a specific body of water. Airsheds can be very large. The Chesapeake Bay’s airshed is 570,000 square miles, stretching west to Ohio and north to Canada.

What produces air pollution?

There are four sources of air pollution in the Chesapeake Bay region. Stationary sources include power plants or manufacturing facilities. Mobile sources include cars, trucks and off-road vehicles; boats; airplanes; gas-powered lawn tools; and construction equipment. Agricultural sources include farm operations that emit gases, chemicals or particulate matter. Natural sources include lightning and dust storms.

How do airborne pollutants move?

Wind and weather can carry airborne pollutants over short or long distances.

How does air pollution affect the Chesapeake Bay?

Air pollution released into the Chesapeake Bay’s airshed will eventually fall back to the earth’s surface, where it could wind up in our rivers and streams. Airborne nitrogen, for example, is one of the largest sources of pollution affecting the Bay. Just over one-third of the nitrogen polluting the Bay comes from the air.

What is atmospheric deposition?

Atmospheric deposition is the process through which air pollution settles onto land or water.

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Terms

Acid rain

Natural rainfall that contains nitric and sulfuric acids due to nitrogen oxide (NOx) and sulfur dioxide discharged into the air by industries, power plants, automobiles and other emission sources.

Airshed

The area of land over which airborne pollutants can travel to reach a particular river, lake, bay or other body of water. The Chesapeake Bay’s airshed is 570,000 square miles, stretching north to Canada, west to Ohio and south to South Carolina.

Atmospheric deposition

The process by which airborne pollutants settle onto land or water. “Wet deposition” refers to pollutants that fall to the earth while attached to raindrops or snowflakes. “Dry deposition” refers to pollutants that fall to the earth without precipitation.

Bioaccumulation

The uptake and storage of chemical contaminants by living animals and plants. This can occur through direct contact with contaminated water or sediment or through the ingestion of another organism that is contaminated. For example, a small fish might eat contaminated algae, a bigger fish might eat several contaminated fish and a human might eat a bigger, now-contaminated fish. Contaminants typically increase in concentration as they move up the food chain.

Chemical contaminants

Pesticides, pharmaceuticals, metals and other toxic substances that can harm the health of both humans and wildlife.

Emissions

Pollution released or discharged into the air from natural or man-made sources, including vehicles, smokestacks and the spraying of aerosols.

Watershed

An area of land that drains into a particular river, lake, bay or other body of water. We all live in a watershed: some are large (like the Chesapeake), while others are small (like your local creek, stream or river).

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