Science News - August 25, 2004

Tracking America’s exported air pollution

A consortium of 100 scientists from 6 countries is cooperating on a 6-week study of air pollution as it leaves the east coast of the United States, flows across the Atlantic Ocean, and hunkers down over Europe. Knowing the quantity of air pollution that America exports towards the east will help European Union officials set reasonable emissions goals for member nations and understand the health effects of this unwanted import.

Alistair Lewis, a professor of chemistry at the University of York (U.K.), says that the heat wave in the summer of 2003 made the deadly effects of air pollution all too clear. Elevated levels of ozone and PM₁₀s are thought to have led to more than 800 deaths in London. While most of the air pollution was produced locally, little is know about how much was imported from abroad. “If you have ozone, it’s difficult to determine where it’s coming from: Some is local, some is regional, some is background,” says Lewis.

NASA's modified DC-8 airplane carries dozens of onboard instruments that allow scientists to instantly analyze air samples for a broad range of different pollutants.

Lewis and 40 other British researchers have positioned themselves in the Azores, a group of islands halfway between North America and Europe. The Americans will begin tracking air masses as they leave the northeast coast of the United States and will then pass off the study to the British. The British plan to track the air to the coast of France, where French and German researchers will then follow the pollution as it travels across Europe. Jim Meagher, air program manager for the National Oceanographic and Atmospheric Administration (NOAA), says that following a specific air mass is obviously quite difficult. But researchers hope that integrating computer weather models along with real time sampling from airplanes will yield high-quality results.

“It’s almost like a kinetic experiment in the lab where you’re watching the chemicals evolve over time: The gas converted to particles, and the nitrogen oxides and VOCs to ozone,” he says.

Research planes will monitor this evolutionary process. Meagher says they will be able to track the same air mass by zeroing in on pollution signatures. For instance, one air mass was tracked because it contained acetonitrile. “This air mass was contaminated by fires in Alaska and Canada,” says Meagher. “Acetonitrile is a marker for biomass burnings.” Another air mass was found to contain sulfate aerosols.

The planes perform real-time sampling every second for dozens of parameters, including ozone, nitrogen oxides, and carbon oxides. Canisters of air are also collected for later measurements of hydrocarbons.

Lewis says the hardest part of the project was calibrating all the equipment out in the middle of the Atlantic. “It’s tough because you have to get the two planes to meet in the air and then fly together for around an hour in the same air mass while checking all the instruments,” he says.

All data will be gathered by the end of August, and the teams plan to meet to discuss results sometime in January. The study will resume in the summer of 2006 when many of the same scientists will track air pollution from Asia as it treks across the Pacific to North America. —PAUL D. THACKER