JIJITANG2014-07-15 6:10 PM


Airplane landings and takeoffs at Los Angeles International Airport (LAX) worsen air quality more than 10 miles east of the airport, a far larger area than previously assumed.

A new study finds a doubling of ultrafine particle number concentrations not only extend further east downwind from the airport boundary over a 20-square mile area, but in certain wind conditions, also to areas south.

“Our research shows that airport impacts extend more than five times further than previously assumed,” says Scott Fruin, lead researcher and assistant professor of preventive medicine at the Keck School of Medicine at the University of Southern California. “Effects from planes that are landing appear to play a major role in this large area of impact.”

To put affected area into perspective, the researchers calculated that one-quarter to one-half of the entire Los Angeles County freeway system produces an equivalent increase in ultrafine particle numbers on a concentration-weighted basis.

“LAX may be as important to LA’s air quality as the freeway system,” Fruin says. “The impact area is large, and the airport is busy most hours of the day. That makes it uniquely hard for people to avoid the effects of air pollution in affected areas.”

Most previous research on the air quality impacts of airports focused on measuring air quality near where jet takeoffs occur. Takeoffs produce immense plumes of exhaust but only intermittently, and pollution concentrations downwind have been observed to fall off rapidly with distance. The assumption has been that total airport impacts also fall off rapidly with distance.

The new research finds that this assumption is wrong.

The study shows that concentrations of ultrafine particles were more than double over 20 square miles compared to background concentrations in nearby areas outside the area of LAX impact. Also, ultrafine particle number concentrations four times higher than background extended a distance of six miles.

“Given the existing concern about the possible health effects of urban ultrafine particle levels, living in an area with two to four times the average LA levels of ultrafine particles is of high public health concern,” says first author Neelakshi Hudda, research associate in preventive medicine.

Ultrafine particles are currently unregulated, but are of concern because they appear to be more toxic than larger particles on an equal mass basis in animal and cellular studies, and because they appear able to enter the bloodstream, unlike large particles that lodge in the lungs.

For the study, published in Environmental Science & Technology, researchers used vehicles equipped with special measurement devices to capture data not available using traditional fixed monitors. The team was able to take moving measurements for more than five hours under consistent wind conditions to fully capture the extent of the impact boundaries.

“Other airports generally have less steady wind directions, which would make these measurements more difficult,” Hudda says. “Similar impacts are probably happening, but their location likely shifts more rapidly than in Los Angeles.

“The on-shore westerly winds cause this impact regularly in communities east of LAX, because the impact’s location corresponds to the wind direction,” she adds. “In the winter months, when the winds were different, impacts were measured south of the airport during northerly winds.”

Tim Larson, Tim Gould, and Kris Hartin from the University of Washington contributed to the study.

Original Article: 
《Emissions from an International Airport Increase Particle Number Concentrations 4-fold at 10 km Downwind》, Published on Journal 《Environmental Science and Technology》in May 29, 2014. 






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