Local sources major cause of US near-ground aerosol pollution

A new NASA study estimates that most ground-level particulate pollution in the United States stems from regional sources in North America and only a small amount is brought to the country from other parts of the world.

Researchers using an innovative global aerosol tracking model have for the first time produced a global estimate of sources and movements of aerosols near the ground where they can affect human health and run afoul of environmental regulations. Previously, researchers studying aerosols moving between continents focused primarily on tracking a single type of aerosol, such as dust or black carbon, or measuring their quantities throughout the atmosphere. This left gaps in understanding where ground-level particulate pollution comes from.

"This is the first study to comprehensively consider the origin, composition and type of fine particles over the United States and connect them to both domestic and foreign sources." said Mian Chin, an atmospheric scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md., and lead author of the study.

Aerosols are airborne particles that arise from both human sources such as burning fossil fuels, and natural sources such as fires, dust and volcanoes. They are also a major source of near-ground pollution. Since 1970, particulate matter has been regulated in the United State s by the Clean Air Act. A more recent concern has been aerosols that arrive here from distant shores carried by the wind.

Chin and colleagues set out to investigate how much and what type of aerosols made the intercontinental journey in 2001. The team employed the help of a computer model using known air chemistry and wind patterns to trace a region's aerosols – everything from fossil fuel and biofuel combustion, biomass burning, and volcanic sources, desert dust and sea salt – back to their sources.

"Using the model, we followed the path of aerosols to find out how much is local and how much is from outside a region," Chin says.

Chin and colleagues estimate that between 65-70 percent of surface particulate matter in the eastern U.S. originates from regional pollution aerosols from fuel combustion in North America. The report was in the Nov. 1 edition of the European Geosciences Union's Atmospheric Chemistry and Physics.

They also found that 30-40 percent of fine particulates in the western U.S. come from local pollution sources. The model results estimated that just 2-6 percent of U.S. surface fine particulates come from fuel combustion particles emitted outside of North America, including Asia and Europe. About 50 percent of surface fine particulate matter in the western U.S. stems from a natural source: dust transported from Asia or from local deserts and organic aerosols from vegetation.

"Our results indicate that controlling regional pollution emissions will be the most effective and most responsible way to manage U.S. air quality," Chin says.

Source: by Kathryn Hansen, Goddard Space Flight Center

Related stories:

Tracking down the menace in Mexico City smog
A new report by scientists who are part of the international MILAGRO Campaign indicates that some of the most harmful air pollution in Mexico City may not come from motor vehicles but instead originates with industrial sources – and that the culprit may be garbage incineration.
Smoke smudges Mexico City's air, chemists identify sources
Mexico City once topped lists of places with the worst air pollution in the world. Although efforts to curb emissions have improved the situation, tiny particles called aerosols still clog the air. Now, atmospheric scientists from UC San Diego and six other institutions have sorted through the pall that hangs over the city to precisely identify aerosols that make up the haze and chart daily patterns of changes to the mix.
Unmanned aircraft to study Southern California smog and its consequences
Using sophisticated unmanned aircraft, research scientists at Scripps Institution of Oceanography, UC San Diego hope to assess Southern California’s potential for climate change and better understand the sources of air pollution.
Air Quality Forecasts See Future in Space
Weather broadcasts have long been a staple for people planning their day. Now with the help of NASA satellites, researchers are working to broaden daily forecasts to include predictions of air quality, a feat that is becoming reality in some parts of the world.
Invisible gases form most organic haze in urban, rural areas
A new study involving the University of Colorado at Boulder shows that invisible, reactive gases hovering over Earth's surface, not direct emissions of particulates, form the bulk of organic haze in both urban and rural areas around the world.
Global 'sunscreen' has likely thinned, report NASA scientists
A new NASA study has found that an important counter-balance to the warming of our planet by greenhouse gases – sunlight blocked by dust, pollution and other aerosol particles – appears to have lost ground.
Researchers build lasers for NASA climate studies
NASA has given researchers at Montana State University $1.14 million to study two important, but poorly understood, pieces in the global-warming puzzle: aerosols and water vapor in the atmosphere.
NASA probes the sources of the world's tiny pollutants
Pinpointing pollutant sources is an important part of the ongoing battle to improve air quality and to understand its impact on climate. Scientists using NASA data recently tracked the path and distribution of aerosols -- tiny particles suspended in the air -- to link their region of origin and source type with their tendencies to warm or cool the atmosphere.

News discussion:

Space & Earth science news