[1] The uptake of gaseous glyoxal onto particulate matter has been studied in laboratory experiments under conditions relevant to the ambient atmosphere using an aerosol mass spectrometer. The growth rates and reactive uptake coefficients, g, were derived by fitting a model of particle growth to the experimental data. Organic growth rates varied from 1.05 Â 10 À11 to 23.1 Â 10 À11 mg particle À1 min À1 in the presence of $5 ppb glyoxal. Uptake coefficients (g) of glyoxal varied from 8.0 Â 10 À4 to 7.3 Â 10 À3 with a median g = 2.9 Â 10 À3 , observed for (NH 4 ) 2 SO 4 seed aerosols at 55% relative humidity.Increased g values were related to increased particle acidity, indicating that acid catalysis played a role in the heterogeneous mechanism. Experiments conducted at very low relative humidity, with the potential to be highly acidic, resulted in very low reactive uptake. These uptake coefficients indicated that the heterogeneous loss of glyoxal in the atmosphere is at least as important as gas phase loss mechanisms, including photolysis and reaction with hydroxyl radicals. Glyoxal lifetime due to heterogeneous reactions under typical ambient conditions was estimated to be t het = 5-287 min. In rural and remote areas the glyoxal uptake can lead to 5-257 ng m À3 of secondary organic aerosols in 8 hours, consistent with recent ambient measurements.Citation: Liggio, J., S.-M. Li, and R. McLaren (2005), Reactive uptake of glyoxal by particulate matter,

Reactive uptake of glyoxal onto particulate matter has been studied in laboratory experiments in a 2 m3 Teflon reaction chamber. Inorganic seed particles of different composition were utilized, including (NH4)2SO4, (NH4)2SO4/ H2SO4, NaNO3, and simulated sea salt, while the relative humidity and acid concentration were varied. The organic composition of the growing particles was measured in situ with an aerosol mass spectrometer, providing particle mass spectra as a means of product identification. Aerosol physical characteristics were also measured with a differential mobility analyzer and condensation nucleus counter. Regardless of seed composition, particle growth was rapid and continuous over the course of several hours. Identification of several mass fragments greater than the glyoxal monomer suggested that heterogeneous reactionsto form glyoxal adducts of lowvolatility had occurred. Temporal analysis of the mass fragments was consistent with a proposed acid-catalyzed mechanism whereby glyoxal is first hydrated, followed by self-reaction to form cyclic acetal structures. Increased relative humidity slowed the formation of higher order oligomers, also consistent with the proposed mechanism. The relative contribution of various oligomers to the overall organic composition was strongly dependent on the relative humidity and hence the particulate water concentration. A mild acid catalysis was also observed upon increasing the acidity of the seed particles. Specific mass fragments were found that could only arise from sulfate esters and were not present on the non-sulfur-containing seed particles. This first evidence of the formation of organic sulfates in particles is presented together with a proposed mechanism and molecular structure. These results suggest that the formation of these products of glyoxal uptake can contribute significantly to secondary organic aerosol.

Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO3-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number of important uncertainties remain. These include an incomplete understanding of the rates, mechanisms, and organic aerosol yields for NO3-BVOC reactions, lack of constraints on the role of heterogeneous oxidative processes associated with the NO3 radical, the difficulty of characterizing the spatial distributions of BVOC and NO3 within the poorly mixed nocturnal atmosphere, and the challenge of constructing appropriate boundary layer schemes and non-photochemical mechanisms for use in state-of-the-art chemical transport and chemistry–climate models.This review is the result of a workshop of the same title held at the Georgia Institute of Technology in June 2015. The first half of the review summarizes the current literature on NO3-BVOC chemistry, with a particular focus on recent advances in instrumentation and models, and in organic nitrate and secondary organic aerosol (SOA) formation chemistry. Building on this current understanding, the second half of the review outlines impacts of NO3-BVOC chemistry on air quality and climate, and suggests critical research needs to better constrain this interaction to improve the predictive capabilities of atmospheric models.

Large-scale oil production from oil sands deposits in Alberta, Canada has raised concerns about environmental impacts, such as the magnitude of air pollution emissions. This paper reports compound emission rates (E) for 69-89 nonbiogenic volatile organic compounds (VOCs) for each of four surface mining facilities, determined with a top-down approach using aircraft measurements in the summer of 2013. The aggregate emission rate (aE) of the nonbiogenic VOCs ranged from 50 ± 14 to 70 ± 22 t/d depending on the facility. In comparison, equivalent VOC emission rates reported to the Canadian National Pollutant Release Inventory (NPRI) using accepted estimation methods were lower than the aE values by factors of 2.0 ± 0.6, 3.1 ± 1.1, 4.5 ± 1.5, and 4.1 ± 1.6 for the four facilities, indicating underestimation in the reported VOC emissions. For 11 of the combined 93 VOC species reported by all four facilities, the reported emission rate and E were similar; but for the other 82 species, the reported emission rate was lower than E. The median ratio of E to that reported for all species by a facility ranged from 4.5 to 375 depending on the facility. Moreover, between 9 and 53 VOCs, for which there are existing reporting requirements to the NPRI, were not included in the facility emission reports. The comparisons between the emission reports and measurementbased emission rates indicate that improvements to VOC emission estimation methods would enhance the accuracy and completeness of emission estimates and their applicability to environmental impact assessments of oil sands developments.volatile organic compounds | emissions | emission inventory validation | oil sands | aircraft measurements

[1] Reliable characterization of particles freshly emitted from the ocean surface requires a sampling method that is able to isolate those particles and prevent them from interacting with ambient gases and particles. Here we report measurements of particles directly emitted from the ocean using a newly developed in situ particle generator (Sea Sweep). The Sea Sweep was deployed alongside R/V Atlantis off the coast of California during May of 2010. Bubbles were generated 0.75 m below the ocean surface with stainless steel frits and swept into a hood/vacuum hose to feed a suite of aerosol instrumentation on board the ship. The number size distribution of the directly emitted, nascent particles had a dominant mode at 55-60 nm (dry diameter) and secondary modes at 30-40 nm and 200-300 nm. The nascent aerosol was not volatile at 230 C and was not enriched in SO 4 = , Ca ++ , K + , or Mg ++ above that found in surface seawater. The organic component of the nascent aerosol (7% of the dry submicrometer mass) volatilized at a temperature between 230 and 600 C. The submicrometer organic aerosol characterized by mass spectrometry was dominated by non-oxygenated hydrocarbons. The nascent aerosol at 50, 100, and 145 nm dry diameter behaved hygroscopically like an internal mixture of sea salt with a small organic component. The CCN/CN activation ratio for 60 nm Sea Sweep particles was near 1 for all supersaturations of 0.3 and higher indicating that all of the particles took up water and grew to cloud drop size. The nascent organic aerosol mass fraction did not increase in regions of higher surface seawater chlorophyll but did show a positive correlation with seawater dimethylsulfide (DMS).

The Uintah Basin in northeastern Utah, a region of intense oil and gas extraction, experienced ozone (O₃) concentrations above levels harmful to human health for multiple days during the winters of 2009–2010 and 2010–2011. These wintertime O₃ pollution episodes occur during cold, stable periods when the ground is snow-covered, and have been linked to emissions from the oil and gas extraction process. The Uintah Basin Winter Ozone Study (UBWOS) was a field intensive in early 2012, whose goal was to address current uncertainties in the chemical and physical processes that drive wintertime O₃ production in regions of oil and gas development. Although elevated O₃ concentrations were not observed during the winter of 2011–2012, the comprehensive set of observations tests our understanding of O₃ photochemistry in this unusual emissions environment. A box model, constrained to the observations and using the near-explicit Master Chemical Mechanism (MCM) v3.2 chemistry scheme, has been used to investigate the sensitivities of O₃ production during UBWOS 2012. Simulations identify the O₃ production photochemistry to be highly radical limited (with a radical production rate significantly smaller than the NO_x emission rate). Production of OH from O₃ photolysis (through reaction of O(¹D) with water vapor) contributed only 170 pptv day⁻¹, 8% of the total primary radical source on average (primary radicals being those produced from non-radical precursors). Other radical sources, including the photolysis of formaldehyde (HCHO, 52%), nitrous acid (HONO, 26%), and nitryl chloride (ClNO₂, 13%) were larger. O₃ production was also found to be highly sensitive to aromatic volatile organic compound (VOC) concentrations, due to radical amplification reactions in the oxidation scheme of these species. Radical production was shown to be small in comparison to the emissions of nitrogen oxides (NO_x), such that NO_x acted as the primary radical sink. Consequently, the system was highly VOC sensitive, despite the much larger mixing ratio of total non-methane hydrocarbons (230 ppbv (2080 ppbC), 6 week average) relative to NO_x (5.6 ppbv average). However, the importance of radical sources which are themselves derived from NO_x emissions and chemistry, such as ClNO₂ and HONO, make the response of the system to changes in NO_x emissions uncertain. Model simulations attempting to reproduce conditions expected during snow-covered cold-pool conditions show a significant increase in O₃ production, although calculated concentrations do not achieve the highest seen during the 2010–2011 O₃ pollution events in the Uintah Basin. These box model simulations provide useful insight into the chemistry controlling winter O₃ production in regions of oil and gas extraction

Atmospheric emissions of gas and particulate matter from a large ocean-going container vessel were sampled as it slowed and switched from high-sulfur to low-sulfur fuel as it transited into regulated coastal waters of California. Reduction in emission factors (EFs) of sulfur dioxide (SO₂), particulate matter, particulate sulfate and cloud condensation nuclei were substantial (≥ 90%). EFs for particulate organic matter decreased by 70%. Black carbon (BC) EFs were reduced by 41%. When the measured emission reductions, brought about by compliance with the California fuel quality regulation and participation in the vessel speed reduction (VSR) program, are placed in a broader context, warming from reductions in the indirect effect of SO₄ would dominate any radiative changes due to the emissions changes. Within regulated waters absolute emission reductions exceed 88% for almost all measured gas and particle phase species. The analysis presented provides direct estimations of the emissions reductions that can be realized by California fuel quality regulation and VSR program, in addition to providing new information relevant to potential health and climate impact of reduced fuel sulfur content, fuel quality and vessel speed reductions.

The applicability of the perfluoro effect to the X-ray spectra (300-800 eV) of unsaturated organic molecules is explored. The Cls and Fls (and 01s where appropriate) oscillator strength spectra of five fluoroethylenes, octafluorocyclopentene, formyl fluoride, carbonyl fluoride, hexafluorobutadiene, trifluoroacetic acid, heduorobutyne-2, hexafluoroacetone, and octatluoronaphthalene were derived from electron impact energy loss spectra recorded under electric-dipole scattering conditions. These spectra are analyzed and compared with those of their perhydro analogs, several of which (naphthalene, acetic acid, butyne-2) are reported for the first time. In unsaturated systems in which all the atoms lie in the molecular plane, such as ethylene, formaldehyde, benzene, etc., perfluorination results in approximately 10 eV shifts of the inner-shell energy loss spectra to higher energies, yet the term values for the Cls-, ln* excitations are shifted by only l eV and often less. In direct contrast, the term values for the equivalent C l s -+ l a * excitations in unsaturated systems having atoms out of the molecular plane, such as butene-2 and acetone, are shifted upward by up to 3 eV upon perfluorination. These different spectral behaviors of planar and nonplanar systems on fluorination quantitatively parallel those which were observed earlier for valence-level ionization potentials (10-20 eV) and attributed to the perfluoro effect. I t is observed for the first time that the Cls+ln* excitation energies in planar hydrocarbons are only very weakly dependent on the spatial extent of the n-electron system. An explanation involving a localized Cls hole is proposed to rationalize this behavior.The perfluoro effect also predicts that excitations to a* MO's will become relatively low-lying in highly fluorinated planar systems. Such low-lying inner-shell excitations induced by fluorination are observed in the fluoroethylene series and in the fluorocarbonyls. When the negative-ion spectra of the fluoroethylenes are assigned in a self-consistent manner, a a* MO is found to drop into the vicinity of In* upon fluorination. A similar intrusion of the lowest dr MO among the n+ MO's is also observed upon fluorinating benzene, while evidence for this in the case of naphthalene is less clear, on account of the complex pattern of multiple Cls-+nn* transitions in this molecule.