Intercontinental influence of NO_x and CO emissions on particulate matter air quality

摘要

Anthropogenic emissions of nitrogen oxides (NO_x = NO + NO_2) and carbon monoxide (CO) affect particulate matter (PM) air quality on an intercontinental scale by changing background concentrations of oxidants (OH, ozone, H_2O_2) and thus increasing the oxidation rate of sulfur dioxide (SO_2) to sulfate and NO_x to nitrate. We conduct sensitivity simulations with the GEOS-Chem chemical transport model and find that these intercontinental influences of NO_x and CO emissions on PM can be greater than those from SO_2 emissions (a direct PM precursor). The intercontinental impact of oxidant precursors is greatest in receptor regions with high domestic SO_2, NO_x, and ammonia emissions and hence already high levels of PM. US NO_x and CO emissions increase annual mean PM in northern Europe and eastern China by up to 0.25 μg m~(-3). The increase in Europe is mostly as sulfate, whereas in China it is mostly as nitrate. East Asian NO_x and CO emissions have a weaker intercontinental influence (~0.2 μg m~(-3) in northern Europe, ~0.1 μg m~(-3) in the eastern US). These intercontinental effects of NO_x and CO emissions on PM depend in a complex way on the chemical environment of receptor regions. Intercomparison of results from different models would be of great interest.