Effect of regional precursor emission controls on long-range ozone transport – Part 1: Short-term changes in ozone air quality

摘要

Observations and models demonstrate that ozone and its precursors can betransported between continents and across oceans. We model the influences of10% reductions in anthropogenic nitrogen oxide (NO) emissions fromeach of nine world regions on surface ozone air quality in that region andall other regions. In doing so, we quantify the relative importance oflong-range transport between all source-receptor pairs, for directshort-term ozone changes. We find that for population-weightedconcentrations during the three-month "ozone-season", the strongestinter-regional influences are from Europe to the Former Soviet Union, EastAsia to Southeast Asia, and Europe to Africa. The largest influences perunit of NO reduced, however, are seen for source regions in thetropics and Southern Hemisphere, which we attribute mainly to greatersensitivity to changes in NO in the lower troposphere, and secondarilyto increased vertical convection to the free troposphere in tropicalregions, allowing pollutants to be transported further. Results show, forexample, that NO reductions in North America are ~20% aseffective per unit NO in reducing ozone in Europe during summer, asNO reductions from Europe itself. Reducing anthropogenic emissions ofnon-methane volatile organic compounds (NMVOCs) and carbon monoxide (CO) by10% in selected regions, can have as large an impact on long-range ozonetransport as NO reductions, depending on the source region. We findthat for many source-receptor pairs, the season of greatest long-rangeinfluence does not coincide with the season when ozone is highest in thereceptor region. Reducing NO emissions in most source regions causes alarger decrease in export of ozone from the source region than in ozoneproduction outside of the source region.