Semivolatile POA and parameterized total combustion SOA in CMAQv5.2: impacts on source strength and partitioning

Atmospheric chemistry and physics, Год журнала: 2017, Номер 17(18), С. 11107 - 11133

Опубликована: Сен. 20, 2017

Abstract. Mounting evidence from field and laboratory observations coupled with atmospheric model analyses shows that primary combustion emissions of organic compounds dynamically partition between the vapor particulate phases, especially as near-source dilute cool to ambient conditions. The most recent version Community Multiscale Air Quality 5.2 (CMAQv5.2) accounts for semivolatile partitioning gas-phase aging these aerosol (POA) consistent experimentally derived parameterizations. We also include a new surrogate species, potential secondary (pcSOA), which provides representation (SOA) anthropogenic sources could be missing current chemical transport predictions. reasons this mass likely following: (1) unspeciated intermediate volatility compound (SVOC IVOC, respectively) inventories, (2) multigenerational products known SOA precursors (e.g., toluene, alkanes), (3) underestimation yields due wall losses in smog chamber experiments, (4) reversible compounds–water interactions and/or aqueous-phase processing emissions. CMAQ predicts spatially averaged contribution pcSOA OA surface concentrations continental United States 38.6 23.6 % 2011 winter summer, respectively. Whereas many past modeling studies focused on particular measurement campaign, season, location, or configuration, we endeavor evaluate important uncertain parameters comprehensive set States-based runs using multiple horizontal scales (4 12 km), mechanisms, seasons years. POA improves predictions hourly over traditional nonvolatile at sites during campaigns southern California (CalNex, May–June 2010), northern (CARES, June southeast US (SOAS, 2013; SEARCH, January July, 2011). Model improvements manifest better correlations correlation coefficient Pasadena night increases 0.38 0.62) reductions underprediction photochemically active afternoon period bias −5.62 −2.42 µg m−3). Daily routine-monitoring networks simulations (CONUS) show modest improvement winter, mean biases reducing 1.14 0.73 m−3, but less change summer when decreases evaporation were similar magnitude added mass. Because model-performance realized by including relatively simple approach is more-complicated parameterizations formation aging, recommend caution applying approaches they currently rely numerous parameters. optimized performance lead higher than observed CONUS evaluation. This may any variations real different regions time periods, too-high other are larger domain, issues such loss processes. discrepancy regionally temporally dependent driven interferences factors like varying regimes.

Язык: Английский

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A review of experimental techniques for aerosol hygroscopicity studies

Atmospheric chemistry and physics, Год журнала: 2019, Номер 19(19), С. 12631 - 12686

Опубликована: Окт. 10, 2019

Abstract. Hygroscopicity is one of the most important physicochemical properties aerosol particles and also plays indispensable roles in many other scientific technical fields. A myriad experimental techniques, which differ principles, configurations cost, are available for investigating hygroscopicity under subsaturated conditions (i.e., relative humidity below 100 %). comprehensive review these techniques provided this paper, broadly classified into four categories, according to way samples investigation prepared. For each technique, we describe its operation principle typical configuration, use representative examples reported previous work illustrate how technique can help better understand hygroscopicity, discuss advantages disadvantages. In addition, future directions outlined discussed further improvement instrumental development.

Язык: Английский

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The impact of biogenic, anthropogenic, and biomass burning volatile organic compound emissions on regional and seasonal variations in secondary organic aerosol

Atmospheric chemistry and physics, Год журнала: 2018, Номер 18(10), С. 7393 - 7422

Опубликована: Май 28, 2018

Abstract. The global secondary organic aerosol (SOA) budget is highly uncertain, with annual SOA production rates, estimated from models, ranging over an order of magnitude and simulated concentrations underestimated compared to observations. In this study, we use a composition-climate model (UKCA) interactive chemistry microphysics provide in-depth analysis the impact each VOC source on its seasonality. We further quantify role spatial distributions, evaluate seasonal against comprehensive set rates monoterpene, isoprene, biomass burning, anthropogenic precursor sources 19.9, 19.6, 9.5, 24.6 Tg a−1, respectively. When all are included, rate 73.6 which lies within range estimates previous modelling studies. burdens biogenic burning peak during Northern Hemisphere (NH) summer. contrast, fairly constant year round. However, burden does have cycle lowest NH summer, probably due enhanced wet removal. Inclusion new also accelerates ageing by condensation primary (POA), making it more hydrophilic, leading reduction in POA lifetime. With monoterpene as only SOA, total (OA) when surface aircraft measurements. Model agreement observations improves added, primarily inclusion although negative bias remains. A sensitivity simulation was performed increased reaction yield, corresponding 70.0 a−1. Whilst improved relative observations, they were still urban environments overestimated downwind remote environments. isoprene did not improve model–observations biases substantially except at one out two tropical locations. these findings may reflect very limited availability model, located mid-latitudes where emissions high. Our results highlight that, current uncertainty limits yields, mid-latitudes, large good needed establish importance

Язык: Английский

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<i>α</i>-Pinene secondary organic aerosol at low temperature: chemical composition and implications for particle viscosity

Atmospheric chemistry and physics, Год журнала: 2018, Номер 18(4), С. 2883 - 2898

Опубликована: Фев. 28, 2018

Abstract. Chemical composition, size distributions, and degree of oligomerization secondary organic aerosol (SOA) from α-pinene (C10H16) ozonolysis were investigated for low-temperature conditions (223 K). Two types experiments performed using two simulation chambers at the Karlsruhe Institute Technology: Aerosol Preparation Characterization (APC) chamber, Interaction Dynamics in Atmosphere (AIDA) chamber. Experiment type 1 simulated SOA formation upper tropospheric conditions: was generated AIDA chamber directly 223 K 61 % relative humidity (RH; experiment termed “cold humid”, CH) comparison 6 RH (experiment dry”, CD) conditions. 2 uplifting: formed APC room temperature (296 K) < “warm WD) or 21 WH) conditions, then partially transferred to kept K, (WDtoCH) 30 (WHtoCH), respectively. Precursor concentrations varied between 0.7 2.2 ppm α-pinene, 2.3 1.8 ozone experiments, Among other instrumentation, a chemical ionization mass spectrometer (CIMS) coupled filter inlet gases aerosols (FIGAERO), deploying I− as reagent ion, used composition analysis. For with lower cold K), smaller particles 100–300 nm vacuum aerodynamic diameter (dva) higher fractions (> 40 %) adducts (molecules more than 10 carbon atoms) oxidation products observed. warm larger (∼ 500 dva) (< 35 produced. We also observed differences (up 20 ∘C) maximum desorption (Tmax) individual compounds desorbing deposited on FIGAERO Teflon different indicating that Tmax is not purely function compound's vapor pressure volatility, but influenced by diffusion limitations within (particle viscosity), interactions matrix), and/or particle filter. Highest under dry adduct fraction; lowest humid fraction. The observations indicate viscosity may be intra- inter-molecular hydrogen bonding oligomers, water uptake, even such Our results suggest physicochemical properties oligomer content mutually influence each other, variation desorptions have implications matrix effects. our demonstrate importance taking experimental into consideration when interpreting data laboratory studies them input climate models.

Язык: Английский

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Growth Kinetics and Size Distribution Dynamics of Viscous Secondary Organic Aerosol

Environmental Science & Technology, Год журнала: 2017, Номер 52(3), С. 1191 - 1199

Опубликована: Дек. 15, 2017

Low bulk diffusivity inside viscous semisolid atmospheric secondary organic aerosol (SOA) can prolong equilibration time scale, but its broader impacts on growth and size distribution dynamics are poorly understood. Here, we present quantitative insights into the effects of evaporation kinetics SOA formed under dry conditions from photooxidation isoprene in presence a bimodal consisting Aitken (ammonium sulfate) accumulation (isoprene or α-pinene SOA) mode particles. Aerosol composition measurements indicate that is composed several semivolatile compounds (SVOCs), with some reversibly reacting to form oligomers. Model analysis shows liquid-like diffusivities be used fit observed particles fail explain by significantly under-predicting evolution mode. In contrast, scenario successfully reproduces both kinetics, interpretation hindered partitioning SVOCs large effectively promotes smaller have shorter diffusion scales. This effect has important implications for ultrafine climatically active sizes.

Язык: Английский

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