Global impact of road traffic emissions on tropospheric ozone

[摘要] Road traffic is one of the major anthropogenic emission sectors for NO_x, CO andNMHCs (non-methane hydrocarbons). We applied ECHAM4/CBM,a general circulation model coupled to a chemistry module,which includes higher hydrocarbons, to investigatethe global impact of 1990 road traffic emissions on the atmosphere.Improving over previous global modelling studies, which concentrated onroad traffic NO_x and CO emissions only, we assess the impact ofNMHC emissions from road traffic.It is revealed that NMHC emissions from road trafficplay a key role for the impact on ozone. They are responsible for(indirect) long-range transport of NO_x from road traffic viathe formation of PAN, which is not found in a simulation without NMHC emissions from roadtraffic.Long-range transport of NMHC-induced PANimpacts on the ozone distribution in Northern Hemisphere regions far away from the sources,especially inarctic and remote maritime regions.In July total road traffic emissions (NO_x, CO and NMHCs) contribute tothe zonally averaged ozone distribution by more than 12%near the surface in the Northern Hemispheremidlatitudes and arctic latitudes. In January road traffic emissions contribute near thesurface in northern and southern extratropics more than 8%.Sensitivity studies for regional emission show that effective transport of road trafficemissions occurs mainly in the free troposphere.In tropical latitudes of Americaup to an altitude of 200 hPa, global road traffic emissions contribute about 8%to the ozone concentration.In arctic latitudes NMHC emissions from road transport are responsible for about 90%of PAN increase from road transport, leading to a contribution to ozone concentrationsof up to 15%.

[学科分类] 大气科学