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Air Pollution

Overview

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.

How does air pollution harm the Chesapeake Bay?

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.

  • First, pollution is emitted into the air, where wind and weather can carry it over long distances.
  • Eventually, airborne pollution particles fall onto the land or into the water, sometimes in the form of dry particles and sometimes attached to rain, snow or other precipitation.
  • Even pollution that falls onto the land—rather than straight onto the water’s surface—can pollute our water, if it soaks into groundwater or if it is washed off of roofs, streets and sidewalks and into storm drains, rivers and streams.

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.

What are the sources of air pollution in the Chesapeake Bay region?

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

Stationary and area sources are “point sources” of air pollution. These identifiable sources have a fixed location and do not move.

  • Stationary sources are large, consistent sources of air pollution, like power plants or chemical or manufacturing facilities.
  • Area sources are smaller sources of air pollution that are often clustered near each other, like dry cleaners or gas stations.

Mobile sources

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

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

Natural sources of air pollution are those that are not caused by human activities. These include lightning, dust storms, forest fires and erupting volcanoes.

What kind of air pollution is affecting Chesapeake Bay health?

Nitrogen and chemical contaminants are two kinds of airborne pollutants that are affecting the Chesapeake Bay and its tributaries.

Nitrogen

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.

  • Nitrogen oxides (or NOx) are produced by machines or processes that are powered by gas, coal or oil, like the running of a car or the heating of a building. Nitrogen oxides account for two-thirds of the airborne nitrogen that ends up in the Bay, and are a big contributor to ground-level ozone pollution.
  • Ammonia emissions are most often generated by livestock or poultry operations. Ammonia accounts for the remaining one-third of the airborne nitrogen that is polluting the Bay.

Chemical Contaminants

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).

  • Mercury is a toxic metal that is released into the air when coal, oil, natural gas and hazardous materials are burned.
  • PCBs are a group of chemicals once used as dielectric and coolant fluids in electrical equipment. While the production of PCBs was banned in the United States in 1977, PCBs continue to persist in the environment.
  • PAHs are a group of chemicals that are released into the air when coal, oil, gasoline and other fossil fuels are burned.

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.

How can we reduce air pollution in the Chesapeake Bay region?

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.

  • Through a process known as attenuation, forests can reduce the amount of pollutants in our air. Trees act like “attenuation machines,” as their roots and leaves and forest soils absorb and trap airborne pollutants. Forests can, for instance, capture more than 85 percent of the nitrogen that falls onto them from the air, blocking it from flowing into our groundwater, rivers and streams. And in urban areas, tree cover can lower summertime temperatures and reduce the generation of ozone and other harmful pollutants.
  • New state and federal regulations, as well as new and improved technologies, are reducing emissions from vehicles and power plants. However, emissions of ammonia from agricultural operations have remained constant. As stronger laws take effect and on-the-ground restoration work continues, air pollution rates are expected to decline.

Take Action

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.

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Chesapeake Bay News


Publications

Deposition of Air Pollutants to the Great Waters: First Report to Congress

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.

Airsheds and Watersheds III - The Significance of Ammonia

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…

Effects of Atmospheric Nitrogen Deposition on Algal Assemblages in Chesapeake Bay

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.

Technical Tools Used in the Development of Virginia's Tributary Strategies: A Synthesis of Airshed, Watershed, and Estuary Model Results

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…

Air Quality in the Chesapeake Bay Region in 2000

Publication date: June 28, 2000 | Type of document: Policy Memorandum

This is a brief description of air quality in the Chesapeake Bay region

Chesapeake Bay Watershed Model Land Use and Model Linkages to the Airshed and Estuarine Models

Publication date: January 01, 2000 | Type of document: Report | Download: Electronic Version

This document contains the method of producing both the Chesapeake Bay Program Land Use and the Phase 4.2 Watershed Model Landuse. It also documents the hindcasting & forecasting of model land use, the development of model segmentation, and…

Cross-Media Models for the Chesapeake Bay Watershed and Airshed

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…

Air Pollution and the Chesapeake Bay

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

Ammonia and the Chesapeake Bay Airshed

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.

Airsheds and Watersheds II: A shared resources workshop

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…

Air Pollution and the Chesapeake Bay Report

Publication date: January 01, 1997 | Type of document: Report

This work contains the following themes as they relate to the Chesapeake Bay: Watersheds

Deposition of Air Pollutants to the Great Waters: Second Report to Congress

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…

Atmospheric Nitrogen Deposition Loadings to the Chesapeake Bay: An Initial Analysis of the Cost Effectiveness of Control Options

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…

Airsheds and Watersheds - The Role of Atmospheric Nitrogen Deposition

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…

New Insights: Science-based evidence of water quality improvements, challenges, and opportunities in the Chesapeake [Executive Summary]

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…




From Around the Web

Bay FAQs

  • How do airborne pollutants move?
  • What produces air pollution?
  • How does air pollution affect Chesapeake Bay health?
  • What is atmospheric deposition?
  • What is an airshed?

 

Bay Terms

  • Airshed
  • Atmospheric deposition
  • Attenuation
  • Bioaccumulation
  • Chemical contaminants
  • Crustaceans
  • Emissions
  • Polychlorinated biphenyls (PCBs)
  • Tributary

 

Bay-Friendly Tips

  • Reduce Air Pollution
  • Use electric or manual lawn mowers and yard tools instead of gas-powered machines that can pollute our air.
  • Reduce Emissions
  • When possible, walk, bike or take public transportation to reduce vehicle emissions that can pollute our air and water.
  • Reduce Emissions
  • Avoid letting your car idle. Idling for even 10 seconds can waste fuel, damage your engine and pollute our air and water.
  • Plant Trees and Shrubs
  • Plant a buffer of trees and shrubs around the edge of your property to capture polluted runoff.

 

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