Analysis of U.S. particulate matter and sensitivity to emissions published in ES&T

We examined the impact of large US emissions changes, similar to those estimated to have occurred between 2005 and 2012, on inorganic PM2.5 sensitivities to further NOx, SO2, and NH3 emissions reductions using GEOS-Chem. Sensitivities to SO2 emissions are larger year-round and across the US in our 2012 compared with the 2005 case, due to more aqueous-phase SO2 oxidation. Sensitivities to winter NOx emissions are larger, more than 2× those of the high emissions case in parts of the northern Midwest. Sensitivities to NH3 emissions are smaller (∼40%) in the 2005 case, year-round, and across the US. Differences in NOx and NH3 sensitivities indicate an altered atmospheric acidity. Larger sensitivities to SO2 and NOx in the low emissions case imply that reducing these emissions may improve air quality more now than they would have in 2005; conversely, NH3 reductions may not improve air quality as much as previously assumed. Our paper on the topic (Holt, Selin and Solomon, 2015) was recently published in Environmental Science and Technology. To read the article, see the journal site.