Global modeling of organic aerosol: the importance of reactive nitrogen (NO<sub>x</sub> and NO<sub>3</sub>)

Abstract

Reactive nitrogen compounds, specifically NO_x 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 NO_x-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

High-resolution inversion of OMI formaldehyde columns to quantify isoprene emission on ecosystem-relevant scales: application to the Southeast US

“…6). This suggests that isoprene OA formation may be only half of the value found by Kim et al (2015), implying that other sources such as terpenes may make more important contributions to OA (Pye et al, 2010(Pye et al, , 2015Xu et al, 2015).…”

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

“…Fast Hg 0 oxidation in the polar spring boundary layer is simulated by specifying high BrO concentrations when conditions for temperature, sea ice cover, sunlight, and atmospheric stability are met . Monthly mean OA concentrations are archived from a separate v9-02 GEOS-Chem simulation including primary emissions from combustion and secondary production from biogenic and anthropogenic hydrocarbons (Pye et al, 2010). An evaluation of modeled OA against aircraft observations globally is presented in Heald et al (2011), which showed no systematic bias in remote environments but an underestimate of median concentrations in polluted regions.…”

Effects of biogenic nitrate chemistry on the NO<sub>x</sub> lifetime in remote continental regions

“…Current estimates are that human creation of reactive nitrogen (both oxidized and reduced nitrogen) increased by over an order of magnitude from ∼ 15 Tg N yr −1 to ∼ 187 Tg N yr −1 between 1860 and 2005 (Galloway et al, 2008). This increase is one of the primary causes of air pollution, contributing directly to the production of urban ozone and secondary organic aerosol (e.g., Carlton et al, 2010;Pye et al, 2010;Pinder et al, 2012;Rollins et al, 2012). The increase in NO x also results in an increase in the global background of OH (e.g., Wild et al, 2001).…”