By studying the contents of atmosphere in highly polluted cities around the world, two ASU professors are bringing a lesser-known air particle into the spotlight: brown aerosols.
Mechanical and aerospace engineer James Anderson and Peter Crozier of the School of Materials collaborated on the research project.
“We have a fairly good understanding that carbon dioxide is the main greenhouse gas, but there are all of these little aerosol particles that are also effecting the climate,” Crozier said.
The research began when Anderson was involved in a series of field experiments flying over China, Korea and Japan in a scientific research aircraft.
The aircraft collected samples of pollutants in the atmosphere over the Yellow Sea, Anderson said.
Crozier’s expertise is in electron microscopy, which is a technique for looking at electrons under a very powerful microscope.
“James goes out and collects the particles and then I analyze them under the electron microscope,” Crozier said.
When Crozier analyzed the particles, they found both black and brown aerosols present.
Aerosols are microscopic particles in the atmosphere that absorb or reflect sunlight and can lead to the formation of clouds.
Organic aerosols are caused by volcanoes and desert dust; however, human-made aerosols are caused by the burning of tropical forests, coal and oil, Crozier said.
This burning emits black aerosols, which are most commonly known, but Crozier and Anderson have also discovered brown aerosols in the pollution samples.
“The reason it’s important is because when things change color, the amount of light and heat it absorbs changes,” Crozier said.
Brown aerosol particles have also been found in Phoenix, but Anderson said they’re not as abundant.
“Pollution is partly a population issue, but it also has to do with technology and emission control,” he said.
Anderson said the control of emission pollution in China is not nearly as good as it is in the U.S.
“I’ve spent a lot of time in China and the pollution there is just terrible,” Anderson said.
Anderson said China’s pollution may have an impact on climate change in the U.S.
“We’re not exactly sure at this point but we think that it affects the cirrus clouds and might cause a cooling effect,” he said.
Anderson was involved in an experiment where he and a team used a scientific aircraft to track pollution plumes coming out of China and traveling to the coasts of California and Alaska.
He said it can also effect precipitation because the formation of clouds depends on the temperature of the air.
In 1999, Anderson was involved in an experiment where he discovered that the presence of black and brown aerosols in the atmosphere delayed the onset of rain near the Indian Ocean.
“That’s a big deal because it changes the whole cycle of planting and growing crops in that region,” he said.
Current computer models that predict how global warming will affect the climate include black aerosols but do not include brown aerosols.
“By further understanding this one kind of combustion product [brown aerosols], we can improve the computer models,” Crozier said.
Crozier said he and Anderson are attempting to get more funding because collecting and analyzing data is a tedious and complicated process.
“Our job is to provide raw data for the computer modelers to characterize what’s out there and how it affects us,” he said.
Reach the reporter at jodi.cisman@asu.edu.
