Many studies consider which sources of ozone, an air pollutant near Earth’s surface and greenhouse gas higher in the atmosphere, should be controlled to reduce pollution. However, a new study, funded by CPO’s AC4 Program, suggests that changes in an ozone removal pathway, called dry deposition, could affect surface ozone concentrations more than a key ozone source does, and thus should be considered when interpreting trends. The authors found that a 50% decrease in dry deposition, potentially due to changes in meteorology or land use, has twice the impact on surface ozone levels in the Southeast United States as does a 25% increase in nitrogen oxide emissions, which form ozone in the presence of sunlight and reactive carbon gases. However, the authors note that quantifying the impact of changes in ozone sinks versus sources over space and time will require long-term measurements of dry deposition. Better understanding of this ozone sink is essential for improved modeling and prediction of air pollution, ecosystem health, and climate.
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