Air pollution doesn’t just cloud the air we breathe. It can also harm our land and water. What goes up must come down, and pollution released into the air—by cars, trucks, gas-powered lawn tools, power plants and other sources—will fall back to the earth’s surface, where it could wind up in our waterways.
Nitrogen and chemical contaminants are two pollutants that harm both air and water. But maintaining the forests that absorb airborne pollutants and enacting regulations to reduce emissions from our vehicles and power plants are two ways that we can reduce air pollution across the watershed.
Air pollution doesn’t just cloud the air we breathe. It can also harm our land and water. What goes up must come down, and pollution released into the air will fall back to the earth’s surface, where it could wind up in our waterways. The process through which air pollution settles onto land or water is called atmospheric deposition.
Atmospheric deposition occurs in several stages.
The area of land over which airborne pollutants can travel to reach the Bay is known as the Chesapeake Bay airshed. The Bay’s airshed is quite large: approximately 570,000 square miles, nine times as large as the watershed itself.
There are four sources of air pollution in the Chesapeake Bay region: stationary and area sources; mobile sources; agricultural sources; and natural sources.
Stationary and area sources are “point sources” of air pollution. These identifiable sources have a fixed location and do not move.
Mobile sources of air pollution move. Collectively, these sources—which include cars, trucks and off-road vehicles; boats; airplanes; gas-powered lawn tools; and farm and construction equipment—can produce a significant amount of air pollution.
Agricultural sources of air pollution include those farm operations that emit gases, chemicals or particulate matter into the air.
Livestock and poultry operations, for instance, often produce ammonia, which is released into the air from animal manure. Exposure to airborne ammonia can irritate our eyes and lungs, and the settling of ammonia onto the earth’s surface can boost nutrient levels on land and in water. This can lead to the over-fertilization of sensitive crops or to the growth of algae blooms that can harm underwater species.
Natural sources of air pollution are those that are not caused by human activities. These include lightning, dust storms, forest fires and erupting volcanoes.
Nitrogen and chemical contaminants are two kinds of airborne pollutants that are affecting the Chesapeake Bay and its tributaries.
Airborne nitrogen is one of the largest sources of pollution affecting the Chesapeake Bay and its tributaries. Excess nitrogen can fuel the growth of algae blooms, which can block sunlight from reaching underwater grasses and create low-oxygen “dead zones” that suffocate marine life.
Scientists estimate that just over one-third of the nitrogen polluting the Bay comes from the air, most often in the form of nitrogen oxides or ammonia.
The three most common chemical contaminants that are polluting the Chesapeake Bay airshed include mercury, polychlorinated biphenyls (or PCBs) and polycyclic aromatic hydrocarbons (or PAHs).
Once in the water, these chemical contaminants can bind to sediment and enter the bodies of small, bottom-dwelling organisms like worms, clams or small crustaceans. Through a process known as bioaccumulation, fish that consume contaminated organisms can accumulate these toxins in their tissues. Because humans that eat contaminated fish can also be exposed to these chemicals, fish consumption advisories are issued in areas where chemical contaminants are a concern.
To clean up the Chesapeake Bay, we must also clean up our air. While human emissions of airborne pollutants are falling, more reductions are needed if we are to meet pollution-reduction standards for the Bay and its tributaries.
Maintaining the forests that absorb airborne pollutants and enacting regulations to reduce emissions from our vehicles and power plants are two ways that we can reduce air pollution across the watershed.
For Chesapeake Bay restoration to be a success, we all must do our part. Our everyday actions can have a big impact on the Bay. By making simple changes in our lives, each one of us can take part in restoring the Bay and its rivers for future generations to enjoy.
To lower air pollution in the Bay watershed, consider learning how to drive the Bay-friendly way; walking, biking or taking public transportation when possible; or using electric or manual lawn mowers and yard tools instead of gas-powered machines.
Case studies show best management practices have lowered pollution in the Chesapeake Bay.
Cutting power plant emissions has lowered nitrogen pollution in some forested watersheds.
The EPA has proposed draft nitrogen and phosphorus limits, called allocations, as part of a "pollution diet".
Air pollution affects each of the 17.7 million people who live in the Chesapeake Bay watershed. But it doesn’t just cloud the air we breathe. Airborne pollutants can also harm our land and water, fueling the growth of harmful algae blooms that create oxygen-depleted dead zones in the Bay. Randy Mosier from the Maryland Department of the Environment (MDE) explains how our watershed is affected by the “airshed” that surrounds it, and how airborne pollutants fall onto our land and into our water.
Produced by Steve Droter and Olivier Giron
Music: “A Moment of Jazz” by Ancelin
Publication date: November 11, 2001 | Type of document: Report
This is a report on Deposition of Air Pollutants to the Great Waters: First Report to Congress.
Publication date: November 01, 2001 | Type of document: Report
The Significance of Ammonia to Coastal and Estuarine Areas is a report on the third Shared Resources workshop on Airsheds & Watersheds. The report covers the potential detrimental effects of ammonia to air quality' the role ammonia plays as…
Publication date: August 01, 2001 | Type of document: Report
The report describes results from five sampling periods and examine the effects of atmospheric nitrogen deposition on changes in algal biomass, as well as major algal classes.
Publication date: September 30, 2000 | Type of document: Report | Download: Electronic Version
The overall modeling framework used to assess Virginia's tributary strategies in 1999 is documented. This synthesis report provides an overview of the Chesapeake Bay Program airshed, watershed, and estuary models and other diagnostic tools…
Publication date: June 28, 2000 | Type of document: Policy Memorandum
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Publication date: January 01, 2000 | Type of document: Report | Download: Electronic Version
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Publication date: November 16, 1999 | Type of document: Report | Download: Electronic Version
A continuous deterministic environmental model of the Chesapeake Bay Watershed (HSPF), linked to an atmospheric deposition model (RADM) is used to examine nutrient loads to the Chesapeake Bay under different management scenarios. Model…
Publication date: June 01, 1999 | Type of document: Brochure
This work contains the following themes as they relate to the Chesapeake Bay: Watersheds, Environmental Stewardship and Sustainability of the Bay/Stewardship
Publication date: June 01, 1997 | Type of document: Report
This report is a review and assessment of the existing literature on the following topics: distribution of sources and atmospheric concentrations and deposition of ammonia and watershed cycling of NHx.
Publication date: March 07, 1997 | Type of document: Report
This report summarizes the findings of the workshop. The first objective of the workshop was to determine connections between issues, programs, agencies, organizations, and jurisdictions to advance their abilities to address atmospheric…
Publication date: January 01, 1997 | Type of document: Report
This work contains the following themes as they relate to the Chesapeake Bay: Watersheds
Publication date: January 01, 1997 | Type of document: Report
Second report to Congress on the atmospheric deposition of pollutants to the Great Waters. This report documents findings since the First Report to Congress and describes recent progress in these issues. This report places emphasis on local…
Publication date: November 01, 1996 | Type of document: Report
Eutrophication -- low dissolved oxygen -- caused by excess nutrients, is the most significant water quality problem facing the Bay. The Chesapeake Bay Program jurisdictions have committed to reduce nitrogen and phosphorus pollution reaching…
Publication date: October 11, 1995 | Type of document: Report
This report summarizes the workshop proceedings which focused on atmospheric nitrogen compounds. Scientists in key policy and regulatory officials explored mechanisms by which air and water pollution control programs worked together to…
Publication date: | Type of document: | Download: Electronic Version
New Insights: Science-based evidence of water quality improvements, challenges and opportunities in the Chesapeake compiles data collected and analyzed by Chesapeake Bay Program partners, including the University of Maryland Center for…