Trends in sulfate and organic aerosol mass in the Southeast U.S.: Impact on aerosol optical depth and radiative forcing

Attwood, A. R.; Washenfelder, R. A.; Brock, C. A.; Hu, Weiwei; Baumann, Karsten; Campuzano‐Jost, P.; Day, Douglas A.; Edgerton, Eric S.; Murphy, D. M.; Palm, Brett B.; McComiskey, Allison; Wagner, Nick; Sá, Suzane S. de; Ortega, A. M.; Martin, Scot T.; Jimenez, José L.; Brown, Steven S.

doi:10.1002/2014gl061669

Cited by 94 publications

(133 citation statements)

References 47 publications

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“…In addition, amino acids contain organic nitrogen and specifically amine groups, which are also consistent with measurements in polar regions of CHNO fragments (Schmale et al, 2013) and amine groups (Shaw et al, 2010;Frossard et al, 2011). Sugar, levoglucosan, phenols and anthropogenic persistent organic compounds were measured in ambient aerosols at Mario Zucchelli Station and Concordia Station Barbaro et al, 2016Barbaro et al, , 2017Barbaro et al, , 2015a. Carboxylic acids with low molecular weights were also measured at Mario Zucchelli Station, Concordia Station, and Dumont d'Urville (Barbaro et al, 2017;Legrand et al, 2012).…”

Section: Introductionsupporting

confidence: 78%

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High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWARE

et al. 2018

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Abstract. Observations of the organic components of the natural aerosol are scarce in Antarctica, which limits our understanding of natural aerosols and their connection to seasonal and spatial patterns of cloud albedo in the region. From November 2015 to December 2016, the ARM West Antarctic Radiation Experiment (AWARE) measured submicron aerosol properties near McMurdo Station at the southern tip of Ross Island. Submicron organic mass (OM), particle number, and cloud condensation nuclei concentrations were higher in summer than other seasons. The measurements included a range of compositions and concentrations that likely reflected both local anthropogenic emissions and natural background sources. We isolated the natural organic components by separating a natural factor and a local combustion factor. The natural OM was 150 times higher in summer than in winter. The local anthropogenic emissions were not hygroscopic and had little contribution to the CCN concentrations. Natural sources that included marine sea spray and seabird emissions contributed 56 % OM in summer but only 3 % in winter. The natural OM had high hydroxyl group fraction (55 %), 6 % alkane, and 6 % amine group mass, consistent with marine organic composition. In addition, the Fourier transform infrared (FTIR) spectra showed the natural sources of organic aerosol were characterized by amide group absorption, which may be from seabird populations. Carboxylic acid group contributions were high in summer and associated with natural sources, likely forming by secondary reactions.

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Section: Introductionsupporting

confidence: 78%

“…More than 155 000 breeding pairs reside in the ice-free areas on Ross Island (Attwood et al, 2014) from October to March (Davis et al, 2001). The three penguin habitats on Ross Island are all less than 100 km from McMurdo Station (Fig.…”

Section: Organic Mass and Compositionmentioning

confidence: 99%

High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWARE

et al. 2018

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“…This thermodynamic behavior is indeed observed in a wide range of environments (Zhang et al, 2002;Martin et al, 2004;Yu et al, 2005). However, surface and aircraft observations in the Southeast in summer find R to be in the range 1.0-1.6 mol mol −1 , even with excess ammonia in the gas phase (Attwood et al, 2014;Kim et al, 2015). Here we examine the prevalence of this departure from expected thermodynamic behavior by analyzing aerosol and wet deposition data across the eastern US with a focus on the Southeast, and we suggest a tentative explanation.…”

Section: Introductionmentioning

confidence: 66%

Inconsistency of ammonium–sulfate aerosol ratios with thermodynamic models in the eastern US: a possible role of organic aerosol

et al. 2017

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Abstract. Thermodynamic models predict that sulfate aerosol (S(VI) ≡ H 2 SO 4 (aq) + HSO − 4 + SO 2− 4 ) should take up available ammonia (NH 3 ) quantitatively as ammonium (NH + 4 ) until the ammonium sulfate stoichiometry (NH 4 ) 2 SO 4 is close to being reached. This uptake of ammonia has important implications for aerosol mass, hygroscopicity, and acidity. When ammonia is in excess, the ammonium-sulfate aerosol ratio R = [NHshould approach 2, with excess ammonia remaining in the gas phase. When ammonia is in deficit, it should be fully taken up by the aerosol as ammonium and no significant ammonia should remain in the gas phase. Here we report that sulfate aerosol in the eastern US in summer has a low ammonium-sulfate ratio despite excess ammonia, and we show that this is at odds with thermodynamic models. The ammonium-sulfate ratio averages only 1.04 ± 0.21 mol mol −1 in the Southeast, even though ammonia is in large excess, as shown by the ammonium-sulfate ratio in wet deposition and by the presence of gas-phase ammonia. It further appears that the ammonium-sulfate aerosol ratio is insensitive to the supply of ammonia, remaining low even as the wet deposition ratio exceeds 6 mol mol −1 . While the ammonium-sulfate ratio in wet deposition has increased by 5.8 % yr −1 from 2003 to 2013 in the Southeast, consistent with SO 2 emission controls, the ammonium-sulfate aerosol ratio decreased by 1.4-3.0 % yr −1 . Thus, the aerosol is becoming more acidic even as SO 2 emissions decrease and ammonia emissions stay constant; this is incompatible with simple sulfate-ammonium thermodynamics. A tentative explanation is that sulfate particles are increasingly coated by organic material, retarding the uptake of ammonia. Indeed, the ratio of organic aerosol (OA) to sulfate in the Southeast increased from 1.1 to 2.4 g g −1 over the 2003-2013 period as sulfate decreased. We implement a simple kinetic mass transfer limitation for ammonia uptake to sulfate aerosols in the GEOS-Chem chemical transport model and find that we can reproduce both the observed ammonium-sulfate aerosol ratios and the concurrent presence of gas-phase ammonia. If sulfate aerosol becomes more acidic as OA / sulfate ratios increase, then controlling SO 2 emissions to decrease sulfate aerosol will not have the co-benefit of suppressing acidcatalyzed secondary organic aerosol (SOA) formation.

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“…Site description and instruments involved during the SOAS campaign are detailed elsewhere (8,(16)(17)(18). Ambient air was continuously drawn with mechanical pumps through two inlets.…”

Section: Methodsmentioning

confidence: 99%

Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets

Lee

Mohr

Lopez‐Hilfiker

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

300

438

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Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene-and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gasparticle equilibrium and (ii) have a short particle-phase lifetime (∼2-4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment. O rganic nitrates (ONs; ON = RONO 2 + RO 2 NO 2 ) are an important reservoir, if not sink, of atmospheric nitrogen oxides (NO x = NO + NO 2 ). ONs formed from isoprene oxidation alone are responsible for the export of 8-30% of anthropogenic NO x out of the US continental boundary layer (1, 2). Regional NO x budgets and tropospheric ozone (O 3 ) production are, therefore, particularly sensitive to uncertainties in the yields and fates of ON (3-6). The yields implemented in modeling studies are determined from laboratory experiments, in which only a few of the first generation gaseous ONs or the total gas-phase ONs and particle-phase organic nitrates (pONs) have been quantified, whereas production of highly functionalized ONs capable of strongly partitioning to the particle phase have been inferred (7-11) or directly measured in the gas phase (12). Addition of a nitrate (-ONO 2 ) functional group to a hydrocarbon is estimated to lower the equilibrium saturation vapor pressure by 2.5-3 orders of magnitude (13). Thus, ON formation can enhance particle-phase partitioning of semivolatile species in regions with elevated levels of nitrogen oxides, contributing to secondary organic aerosol (SOA) growth (8). However, highly time-resolved measurements of speciated ON in the particle phase have been lacking.We use a recently developed high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) using iodide-adduct ionization (14) with a filter inlet for gases and aerosols (FIGAERO) (15) that allows alternating in situ measurements of the molecular SignificanceWe present online field observations of the speciated molecular composition of organic nitrates in ambient atmospheric particles utilizing recently developed high-resolution MS-based instrumentation. We find that never-before-identified low-volatility organi...

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Trends in sulfate and organic aerosol mass in the Southeast U.S.: Impact on aerosol optical depth and radiative forcing

Cited by 94 publications

References 47 publications

High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWARE

High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWARE

Inconsistency of ammonium–sulfate aerosol ratios with thermodynamic models in the eastern US: a possible role of organic aerosol

Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets

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