Abstract
Abstract. Reactive nitrogen compounds, specifically NOx and NO3, likely influence global organic aerosol levels. To assess these interactions, GEOS-Chem, a chemical transport model, is updated to include improved biogenic emissions (following MEGAN v2.1/2.04), a new organic aerosol tracer lumping scheme, aerosol from nitrate radical (NO3) oxidation of isoprene, and NOx-dependent monoterpene and sesquiterpene aerosol yields. As a result of significant nighttime terpene emissions, fast reaction of monoterpenes with the nitrate radical, and relatively high aerosol yields from NO3 oxidation, biogenic hydrocarbon-NO3 reactions are expected to be a major contributor to surface level aerosol concentrations in anthropogenically influenced areas such as the United States. By including aerosol from nitrate radical oxidation in GEOS-Chem, terpene (monoterpene + sesquiterpene) aerosol approximately doubles and isoprene aerosol is enhanced by 30 to 40% in the Southeast United States. In terms of the global budget of organic aerosol, however, aerosol from nitrate radical oxidation is somewhat minor (slightly more than 3 Tg/yr) due to the relatively high volatility of organic-NO3 oxidation products in the yield parameterization. Globally, 69 to 88 Tg/yr of organic aerosol is predicted to be produced annually, of which 14–15 Tg/yr is from oxidation of monoterpenes and sesquiterpenes and 8–9 Tg/yr from isoprene.
Highlights
The aerosol phase is an important intermediate or terminal form for many species in the atmosphere including volatile organic compounds (VOCs) (Goldstein and Galbally, 2007), and understanding aerosol formation is important for assessing the climate change and human health impacts of air pollution
Global sesquiterpene emissions differ by less than 10% different from previous estimates based on the other reactive volatile organic compound (ORVOC) inventory of Guenther et al (1995) and the speciation of Griffin et al (1999b)
The global chemical transport model, GEOS-Chem, has been used to simulate global organic aerosol from monoterpenes, sesquiterpenes, isoprene, benzene, toluene, xylene, intermediate volatility compounds, and semivolatile organic compounds as well as traditional primary organic aerosol with a focus on biogenic aerosol
Summary
The aerosol phase is an important intermediate or terminal form for many species in the atmosphere including volatile organic compounds (VOCs) (Goldstein and Galbally, 2007), and understanding aerosol formation is important for assessing the climate change and human health impacts of air pollution. Low-volatility compounds emitted from sources including diesel combustion and biomass burning lead to significant amounts of POA and SOA (Robinson et al, 2007) In addition to these hydrocarbons, biogenic compounds such as isoprene (aerosol yield about 4 to 10% depending on oxidant), monoterpenes (yield generally about 10 to 20%), and sesquiterpenes (yield generally higher than 40%) serve as SOA precursors (Hoffmann et al, 1997; Griffin et al, 1999a; Kroll et al, 2006). The Results section is devoted to examining the global organic aerosol (OA) budget and surface concentrations over the US
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
