Biogenic Emissions and Urban Air Quality

Trees emit a species-specific mixture of biogenic volatile organic compounds (BVOCs) like isoprene, monoterpenes and sesquiterpenes. These highly reactive BVOCs are quickly degraded by OH- NO3- and O3 radicals and hence, alter the atmospheric composition. Under high NOx conditions their chemical degradation causes the formation of ground-level ozone. Furthermore, due to progressing chemical reactions BVOCs become less volatile and form secondary organic aerosol (SOA), which is one of the main components of PM2.5. In this way, BVOCs can have negative effects on air quality and thus on human health and the ecosystem through their influence on NOx, O3 and PM2.5 concentrations. However, since BVOC emission is trees species-specific, this influence depends on the composition of the tree population. Air quality may even improve due to a selection of specific tree species. Studies with different land use datasets are performed with the model system COSMO-MUSCAT for Germany and May 2014. The consideration of isoprene, sesquiterpene, HOMs and the reaction of monoterpene with NO3 results in a doubling of organic matter (OM) concentration compared to the original SORGAM mechanism at higher temperatures.