Bay Journal

Web page illustrates air pollution control benefits to Bay

  • By Karl Blankenship on October 12, 2015

Significant reductions in the amount of nitrogen reaching the Bay have come from places few people think about as sources of Chesapeake pollution.

Places like Ohio, Kentucky, Indiana and North Carolina.

As much as a third of the nitrogen that once entered the Chesapeake originated as air pollution, much of it from places outside the watershed, according to estimates from the state-federal Bay Program partnership.

But air pollution reductions from states in and around the Bay drainage basin have steadily reduced the amount of nitrogen emissions going into the air — and the amount of nitrogen landing on the Bay and its watershed.

This nitrogen has two main components:

• Nitrogen oxides, or NOx, which are a byproduct of fossil fuel combustion and come from power plants, vehicles, industries, ships, even lawn mowers.

• Ammonia, which primarily comes from agriculture, though there are some industrial sources as well.

Under the Clean Air Act, NOx emissions have been slashed during the last two decades, primarily to reduce ozone and particulate pollution. Ammonia emissions have stayed the same or risen slightly.

The Bay Program has launched a story map on its website, Cleaner Air, Clean Bay, which provides videos and graphics to show how efforts to control NOx emissions have resulted in less nitrogen deposition on the Bay and its watershed, helping to reduce overall pollution to the Chesapeake.

Visitors to the site can learn more about where air pollution originates, and how NOx emissions have been reduced by various sources over time. They can also use an interactive map to see how the amount of nitrogen deposition has changed in various parts of the watershed over time.

Air pollution was once considered an “uncontrollable” source of pollution to the Bay, but two decades of ramped up air pollution controls have actually made it one of the most important sources of nitrogen reductions for the Chesapeake. As I reported in 2013, air pollution controls have accounted for about a third of the nitrogen reductions to the Bay since 1985.

Other recent research in nine forested watersheds found that air pollution controls reduced nitrogen concentrations by about half since the late 1990s — a greater reduction than many people anticipated.

NOx emissions once accounted for three quarters of all nitrogen deposition in the watershed, while ammonia accounted for about a quarter. Today, the amount of NOx and ammonia deposition is nearly evenly divided in the watershed. Ammonia remains largely unregulated.

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About Karl Blankenship

Karl Blankenship is editor of the Bay Journal and Executive Director of Chesapeake Media Service. He has served as editor of the Bay Journal since its inception in 1991. .(JavaScript must be enabled to view this email address).

Read more articles by Karl Blankenship


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