Seminar

Abstract

Exposure to elevated levels of ozone leads to yield reduction in agricultural crops and biomass loss in trees. Using simulations with the GEOS-Chem model for 2010 and exposure-response functions we quantify the impact of ozone pollution on two major U.S. crops, wheat and soybean, and two ozone-sensitive tree species, ponderosa pine and quaking aspen. Source-receptor relationships are calculated with the GEOS-Chem adjoint model and are separated by location, species, and sectors. These relationships show that the nationwide loss in each vegetation type is influenced most by domestic anthropogenic NOx (>75%), and that long-range transport from foreign sources is small relative to domestic influences. Next, we investigate how future changes in anthropogenic emissions of ozone precursors will likely impact seasonal vegetative ozone exposure, W126, in the western U.S. We use source-receptor relationships to project changes in W126 through midcentury following representative concentration pathway (RCP) emissions. We find that while the overall behavior of W126 is governed by declining domestic emissions, foreign emissions of NOx, NMVOC, and CO and CH4 abundance can either slow or enhance this trend, depending on scenario. The relative importance of foreign emissions increases as U.S. emissions decline, and, in some cases, the contribution of foreign sources exceeds that of domestic as early as 2020.