Investigating the link between dairy cows and aerosols
By Jane Palmer
It doesn’t take a scientist to tell residents of California’s Los Angeles Basin that cows cause air pollution—their noses can do that.
But CIRES scientist John Nowak might be able to tell them whether, along with the unpleasant smell, the ammonia gas coming from the dairy farms leads to more pollution down the line: pollution in the form of aerosols.
Scientists have often found one particular kind of aerosol—ammonium nitrate—in the L.A. Basin at levels more than 10 times higher than in Houston, another city suffering from air quality issues, Nowak said.
This result is due to dairy farms in the region, which provide a large source of ammonia to an already polluted area, he said. But there are still many unknowns in the processes that cause ammonia from the dairy farms to increase aerosols, he said. “There is little information on the transport of ammonia and the effects on aerosols,” he said.
To investigate this uncharted territory further, Nowak and his colleagues didn’t just sit around dairy farms but took to the skies in NOAA’s WP- 3D airplane as part of CalNex 2010 (see The lowdown on CalNex). “To my knowledge, we are the only ones who fly an ammonia instrument in the U.S.,” Nowak said.
Surfing high above and downwind from the unsuspecting cows, they measured the concentrations of ammonia and nitric acid, which together can react to form ammonium nitrate aerosol. They also measured aerosol concentrations and composition. We need all four measurements to understand aerosol formation processes, Nowak said.
“That gives us a lot of unique data,” Nowak said. “Now we have field data to test how aerosols are made in the atmosphere.”
