Study sees how ozone pollution forms at bay

Measurements can help show how upwind states contribute to smog

The sky above Hart-Miller Island became a busy laboratory for several weeks this summer as researchers launched balloons, drones and planes to better understand the complex swirl of air pollution over the Chesapeake Bay.

State and federal agencies initiated a research study aimed at providing more detailed data on how and why the Chesapeake Bay seems to act as a magnet for ozone pollution, amplifying the smog before it is then blown back over land.

“The study is an exciting example of cutting-edge research on the interface between land and water,” said Maryland Environment Secretary Ben Grumbles.

The study attempts to understand in a three-dimensional way what happens to the emissions of power plants, cars and other pollutants once they gather over the Chesapeake Bay.

The results could help Maryland make the case for forcing sources of air pollution in states upwind to better control their emissions.

Maryland officials blame air pollution from upwind states for more than twothirds of the smog that forms over the Baltimore and Washington regions. On hot summer days, the sunlight and heat trigger chemical reactions between pollutants and other compounds in the air, multiplying what is known as ground-level ozone.

Ozone is a form of oxygen found naturally in the upper atmosphere that protects the Earth from ultraviolet radiation, but ground-level ozone is a key ingredient in smog and can cause or aggravate breathing or heart problems in humans. Already this year there have been eight days when Baltimore’s air quality exceeded U.S. Environmental Protection Agency standards.

Ozone is created by the chemical reactions between pollutants known as nitrogen oxides and volatile organic compounds. Nitrogen oxides come from the combustion of fossil fuels in cars and power plants. The nitrogen often falls out of the air as ozone is created.

About a third of the bay’s nitrogen pollution falls from the air onto the land and water, said Ariel Solaski, a staff litigation attorney at the Chesapeake Bay Foundation. Excess nitrogen in the bay contributes to algae blooms and dead zones.

Significant improvements in water quality have been seen since nutrients including nitrogen have been reduced in the rivers and streams flowing into the bay.

While the bay’s watershed is big, its airshed is nine times as large, encompassing 570,000 square miles, Solaski said. The result is that sources of polluting emissions in states as far away as Indiana, Kentucky and Tennessee can harm the bay.

“For the Bay Foundation, any study that is quantifying and pinpointing the sources of the nitrogen oxide pollution is important in understanding how to most effectively reduce nitrogen loads to the bay watershed,” Solaski said.

Maryland and Delaware filed a petition in 2016 asking the EPA to force 19 coal-fired power plants in five states to run their pollution control devices every day during the summer rather than on selected days. The two states argue that they cannot reduce their air pollution without reductions in other states upwind.

The EPA said in early June that it would reject the request, noting that Maryland and Delaware did not prove that the plants pollute at levels violating what is known as the “good neighbor” provision of the Clean Air Act. Maryland is pushing the EPA to reverse the decision, but Grumbles said the state is likely to take legal action if the EPA does not come around.

The state’s research on air pollution formed the basis for the petition, he said.

Scientists have been relying on computer models to predict where pollutants end up in the atmosphere. By taking measurements and analyzing the results, researchers will get a clearer picture of exactly what is happening, according to John Sullivan, a researcher at the National Aeronautics and Space Administration who is a principal investigator for the study.

What is known is that during the summer months emissions from Baltimore are swept out over the water, where they collect in higher concentrations and create a smog mixture, Sullivan said. Then in the late afternoon, as the wind blows from east to west, the smog is blown back over land.

The research is being conducted by the Maryland Department of Environment, NASA, and the National Oceanic and Atmospheric Administration, in collaboration with several universities including UMBC, the University of Maryland, College Park and Howard University. The measurements by balloons, drones, planes and laser-based radar known as lidar are completed, and the data will be available in the coming months.

UMBC researchers helped with the project using lidar — or pulses of laser light — to measure the atmosphere and wind from the surface of the earth up to 3 kilometers high, said Ruben Delgado, an assistant research professor at UMBC. “The wind measurements allow us to have a better understanding of the flow of the air in the Chesapeake Bay,” he said.

Because measurements are made at different heights, scientists will get a three-dimensional picture of the layers of the atmosphere, and the mixing that occurs. Those more precise measurements allow researchers to forecast more accurately where emissions from different sources will end up.

The information will be used both for science and for regulatory enforcement, Grumbles said. “Maryland has proven to be a leader in investing in the science and the people and the hardware to track the ozone,” Grumbles said. “The information we are gathering will be beneficial to to other states with large bodies of water.”