New insights into aerosol formation in the atmosphere
Scientists from Forschungszentrum Jülich and the universities of Manchester and Gothenburg in collaboration with other international researchers have made an important discovery for a better understanding of aerosol formation and therefore the fine particle burden in the atmosphere. The climatologists took a new approach: they were the first to consider the fact that the atmosphere contains biogenic as well as anthropogenic trace gases and vapours in various mixtures.
In their study, they revealed why the amount of aerosols formed in atmospheric mixtures can be significantly smaller than expected from previous laboratory studies. These new insights contribute to more precise and thus more reliable climate models - an important prerequisite for better climate protection and improved air quality.
The influence of aerosol particles on the climate is the largest contributory uncertainty to manmade climate forcing. Moreover, such fine particulate matter is known to seriously affect human health: every year, causing millions of premature deaths worldwide. "Ours is the first study to look at the influence of complex mixtures on the particle mass burden," explains Prof. Thomas Mentel from Jülich's Institute of Energy and Climate Research - Troposphere.
Secondary organic aerosols form efficiently when large biogenic molecules - terpenes - react with OH radicals in the air, the "detergent of the atmosphere". The new study shows that in a mixture with terpenes, the presence of small molecules such as biogenic isoprene, methane, or anthropogenic carbon monoxide, leads to a significant reduction in the amount of aerosol particles in the trace gas mixtures. "We found that isoprene and terpenes not only compete for the OH radicals but also that the intermediate products of these OH reactions react with one another to prevent efficient particle formation," says Mentel.
The Gothenburg team of researchers integrated the observed effects into a global air quality model. Mentel explains: "We were thus able to show that the results from the basic experiments can be applied to real atmospheric conditions. The insights will lead to a better understanding of the influence that aerosols have on climate and air quality."
In light of the new insights, the Jülich scientist is calling for a fundamental change in thinking as well as a different conceptual approach to the problems associated with aerosol particles: "The legitimate desire to isolate processes to investigate them in more detail often leads to a disregard of the fact that mixtures reflect the real condition of the atmosphere. Our findings now show that in order to design experimental systems to quantify the potential atmospheric particle loading, we need to know what mix of manmade and natural trace compounds we want to address."
Source: Forschungszentrum Jülich