ew study shows molecular details of how organic aerosol helps heat up and color haze over megacities
Sitting on an airplane flying into nearly every major city on a sunny day, passengers can see a lingering brown haze. This haze event is linked to climate issues, as the thousands of chemicals involved act as a warming blanket, absorbing sunlight and trapping surface heat. Yet, the chemistry of this haze is not well known. Recently, scientists at Pacific Northwest National Laboratory examined the chemistry of brown carbon, a pernicious set of particles in the haze. They focused on the specks that form around the chemical toluene, a common pollutant. They found that adding a bit of nitrogen oxide, released in combustion engine car exhaust, resulted in particles that trapped some heat. Increasing the nitrogen oxides level, however, resulted in particles that held significantly more heat and caused the mix to turn yellowish brown.