Numerous scientific upgrades to the representation of secondary organic aerosol (SOA) are incorporated into the Community Multiscale Air Quality (CMAQ) modeling system. Additions include several recently identified SOA precursors: benzene, isoprene, and sesquiterpenes; and pathways: in-cloud oxidation of glyoxal and methylglyoxal, particle-phase oligomerization, and acid enhancement of isoprene SOA. NO(x)-dependent aromatic SOA yields are also added along with new empirical measurements of the enthalpies of vaporization and organic mass-to-carbon ratios. For the first time, these SOA precursors, pathways and empirical parameters are included simultaneously in an air quality model for an annual simulation spanning the continental U.S. Comparisons of CMAQ-modeled secondary organic carbon (OC(sec)) with semiempirical estimates screened from 165 routine monitoring sites across the U.S. indicate the new SOA module substantially improves model performance. The most notable improvement occurs in the central and southeastern U.S. where the regionally averaged temporal correlations (r) between modeled and semiempirical OC(sec) increase from 0.5 to 0.8 and 0.3 to 0.8, respectively, when the new SOA module is employed. Wintertime OC(sec) results improve in all regions of the continental U.S. and the seasonal and regional patterns of biogenic SOA are better represented.

This paper presents the first National Emissions Inventory (NEI) of fine particulate matter (PM 2.5 ) that includes the full suite of PM 2.5 trace elements (atomic number >10) measured at ambient monitoring sites across the U.S. PM 2.5 emissions in the NEI were organized and aggregated into a set of 84 source categories for which chemical speciation profiles are available (e.g., Unpaved Road Dust, Agricultural Soil, Wildfires). Emission estimates for ten metals classified as Hazardous Air Pollutants (HAP) were refined using data from a recent HAP NEI. All emissions were spatially gridded, and U.S. emissions maps for dozens of trace elements (e.g., Fe, Ti) are presented for the first time. Nationally, the trace elements emitted in the highest quantities are silicon (3.8 × 10 5 ton/yr), aluminum (1.4 × 10 5 ton/yr), and calcium (1.3 × 10 5 ton/yr). Our chemical characterization of the PM 2.5 inventory shows that most of the previously unspeciated emissions are comprised of crustal elements, potassium, sodium, chlorine, and metalbound oxygen. This work also reveals that the largest PM 2.5 sources lacking specific speciation data are off-road dieselpoweredmobileequipment,roadconstructiondust,marinevessels, gasoline-powered boats, and railroad locomotives.

h i g h l i g h t s Comprehensive review of studies of satellite data applied to emissions estimation. Overview of retrievals for eight major tropospheric air pollutants. Techniques to enhance the usefulness of satellite retrievals. Identification of target source categories for satellite data application. Recommendations on ways to improve the usability of satellite retrievals.