scholarly journals Can Semi-Volatile Organic Aerosols Lead to Less Cloud Particles?

2018 ◽  
Author(s):  
Chloe Y. Gao ◽  
Susanne E. Bauer ◽  
Kostas Tsigaridis
Keyword(s):  
Organic Aerosols ◽  
Number Concentration ◽  
Basis Set ◽  
Mixing State ◽  
Aerosol Mass ◽  
Clean Environment ◽  
Low Cloud ◽  
Low Humidity ◽  
The Impact ◽  
Aerosol Mixing State

Abstract. The impact of condensing organic aerosols on activated cloud number concentration is examined in a new aerosol microphysics box model, MATRIX-VBS. The model includes the volatility-basis set (VBS) framework coupled with the aerosol microphysical scheme MATRIX (Multiconfiguration Aerosol TRacker of mIXing state) that resolves aerosol mass and number concentrations and aerosol mixing state. By including the condensation of organic aerosols, the new model produces less activated particles compared to the original model, which treats organic aerosols as non-volatile. Parameters such as aerosol chemical composition, mass and number concentrations, and particle sizes which affect activated cloud number concentration are thoroughly tested via a suite of Monte-Carlo simulations. Results show that by considering semi-volatile organics in MATRIX-VBS, there is lower activated particle number concentration, except in cases with low cloud updrafts, in clean environment at above freezing temperatures, and in polluted environments at high temperature (310 K) and extremely low humidity conditions.

scholarly journals Can semi-volatile organic aerosols lead to fewer cloud particles?

2018 ◽  
Vol 18 (19) ◽  
pp. 14243-14251 ◽  
Author(s):  
Chloe Y. Gao ◽  
Susanne E. Bauer ◽  
Kostas Tsigaridis
Keyword(s):  
Organic Aerosols ◽  
Number Concentration ◽  
Basis Set ◽  
Mixing State ◽  
Aerosol Mass ◽  
Volatile Organic ◽  
Low Cloud ◽  
Low Humidity ◽  
The Impact ◽  
Aerosol Mixing State

Abstract. The impact of condensing organic aerosols on activated cloud number concentration is examined in a new aerosol microphysics box model, MATRIX-VBS. The model includes the volatility basis set (VBS) framework coupled with the aerosol microphysical scheme MATRIX (Multiconfiguration Aerosol TRacker of mIXing state) that resolves aerosol mass and number concentrations and aerosol mixing state. By including the condensation of organic aerosols, the new model produces fewer activated particles compared to the original model, which treats organic aerosols as nonvolatile. Parameters such as aerosol chemical composition, mass and number concentrations, and particle sizes that affect activated cloud number concentration are thoroughly tested via a suite of Monte Carlo simulations. Results show that by considering semi-volatile organics in MATRIX-VBS, there is a lower activated particle number concentration, except in cases with low cloud updrafts, in clean environments at above-freezing temperatures, and in polluted environments at high temperatures (310 K) and extremely low-humidity conditions.

scholarly journals Towards a better understanding of the origins, chemical composition and aging of oxygenated organic aerosols: case study of a Mediterranean industrialized environment, Marseille

2013 ◽  
Vol 13 (15) ◽  
pp. 7875-7894 ◽  
Author(s):  
I. El Haddad ◽  
B. D'Anna ◽  
B. Temime-Roussel ◽  
M. Nicolas ◽  
A. Boreave ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Aerosols ◽  
Industrial Emissions ◽  
Aerosol Mass Spectrometer ◽  
Statistical Confidence ◽  
Aerosol Mass ◽  
Novel Approach ◽  
Organic Markers ◽  
The Impact ◽  
First Time

Abstract. As part of the FORMES summer 2008 experiment, an Aerodyne compact time-of-flight aerosol mass spectrometer (cToF-AMS) was deployed at an urban background site in Marseille to investigate the sources and aging of organic aerosols (OA). France's second largest city and the largest port in the Mediterranean, Marseille, provides a locale that is influenced by significant urban industrialized emissions and an active photochemistry with very high ozone concentrations. Particle mass spectra were analyzed by positive matrix factorization (PMF2) and the results were in very good agreement with previous apportionments obtained using a chemical mass balance (CMB) approach coupled to organic markers and metals (El Haddad et al., 2011a). AMS/PMF2 was able to identify for the first time, to the best of our knowledge, the organic aerosol emitted by industrial processes. Even with significant industries in the region, industrial OA was estimated to contribute only ~ 5% of the total OA mass. Both source apportionment techniques suggest that oxygenated OA (OOA) constitutes the major fraction, contributing ~ 80% of OA mass. A novel approach combining AMS/PMF2 data with 14C measurements was applied to identify and quantify the fossil and non-fossil precursors of this fraction and to explicitly assess the related uncertainties. Results show with high statistical confidence that, despite extensive urban and industrial emissions, OOA is overwhelmingly non-fossil, formed via the oxidation of biogenic precursors, including monoterpenes. AMS/PMF2 results strongly suggest that the variability observed in the OOA chemical composition is mainly driven in our case by the aerosol photochemical age. This paper presents the impact of photochemistry on the increase of OOA oxygenation levels, formation of humic-like substances (HULIS) and the evolution of α-pinene SOA (secondary OA) components.

scholarly journals MATRIX-VBS (v1.0): implementing an evolving organic aerosol volatility in an aerosol microphysics model

2017 ◽  
Vol 10 (2) ◽  
pp. 751-764 ◽  
Author(s):  
Chloe Y. Gao ◽  
Kostas Tsigaridis ◽  
Susanne E. Bauer
Keyword(s):  
Organic Matter ◽  
Volatile Component ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Basis Set ◽  
Oh Radicals ◽  
Mixing State ◽  
Organic Species ◽  
Parallel Simulations ◽  
Southeastern Us

Abstract. The gas-particle partitioning and chemical aging of semi-volatile organic aerosol are presented in a newly developed box model scheme, where its effect on the growth, composition, and mixing state of particles is examined. The volatility-basis set (VBS) framework is implemented into the aerosol microphysical scheme MATRIX (Multiconfiguration Aerosol TRacker of mIXing state), which resolves mass and number aerosol concentrations and in multiple mixing-state classes. The new scheme, MATRIX-VBS, has the potential to significantly advance the representation of organic aerosols in Earth system models by improving upon the conventional representation as non-volatile particulate organic matter, often also with an assumed fixed size distribution. We present results from idealized cases representing Beijing, Mexico City, a Finnish forest, and a southeastern US forest, and investigate the evolution of mass concentrations and volatility distributions for organic species across the gas and particle phases, as well as assessing their mixing state among aerosol populations. Emitted semi-volatile primary organic aerosols evaporate almost completely in the intermediate-volatility range, while they remain in the particle phase in the low-volatility range. Their volatility distribution at any point in time depends on the applied emission factors, oxidation by OH radicals, and temperature. We also compare against parallel simulations with the original scheme, which represented only the particulate and non-volatile component of the organic aerosol, examining how differently the condensed-phase organic matter is distributed across the mixing states in the model. The results demonstrate the importance of representing organic aerosol as a semi-volatile aerosol, and explicitly calculating the partitioning of organic species between the gas and particulate phases.

scholarly journals The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

2012 ◽  
Vol 12 (19) ◽  
pp. 8911-8949 ◽  
Author(s):  
K. Zhang ◽  
D. O'Donnell ◽  
J. Kazil ◽  
P. Stier ◽  
S. Kinne ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Uptake ◽  
Climate Model ◽  
Organic Aerosols ◽  
Lower Troposphere ◽  
Cloud Microphysics ◽  
Number Concentration ◽  
Sea Salt ◽  
Microphysics Scheme ◽  
Aerosol Mass

Abstract. This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation. Results indicate that from HAM1 to HAM2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced κ-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker in-cloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7) between accumulation mode and coarse mode emission fluxes of aerosol number concentration. This leads to a general increase in the number concentration of smaller particles over the oceans in HAM2, as reflected by the higher Ångström parameters. Evaluation against observation reveals that in terms of model performance, main improvements in HAM2 include a marked decrease of the systematic negative bias in the absorption aerosol optical depth, as well as smaller biases over the oceans in Ångström parameter and in the accumulation mode number concentration. The simulated geographical distribution of aerosol optical depth (AOD) is better correlated with the MODIS data, while the surface aerosol mass concentrations are very similar to those in the old version. The total aerosol water content in HAM2 is considerably closer to the multi-model average from Phase I of the AeroCom intercomparison project. Model deficiencies that require further efforts in the future include (i) positive biases in AOD over the ocean, (ii) negative biases in AOD and aerosol mass concentration in high-latitude regions, and (iii) negative biases in particle number concentration, especially that of the Aitken mode, in the lower troposphere in heavily polluted regions.

scholarly journals Characterizing the volatility and mixing state of ambient fine particles in summer and winter of urban Beijing

2021 ◽  
Author(s):  
Lu Chen ◽  
Fang Zhang ◽  
Don Collins ◽  
Jieyao Liu ◽  
Sihui Jiang ◽  
...  
Keyword(s):  
Atmospheric Aerosols ◽  
Fine Particles ◽  
Number Concentration ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Diurnal Cycles ◽  
Size Dependent ◽  
Before And After ◽  
Aerosol Mixing State

Abstract. Understanding the volatility and mixing state of atmospheric aerosols is important for elucidating the formation of fine particles and to help determining their effect on environment and climate. In this study, the volatility of the fine particles is characterized by the size-dependent volatility shrink factor (VSF) for summer and winter in the urban area of Beijing using measurements of a volatility tandem differential mobility analyzer (VTDMA). We show the volatility of aerosols is always with one high-volatile and one less- or non-volatile mode both in the summer and winter. On average, the particles are more volatile in the summer (with mean VSF of 0.3) than in the winter (with mean VSF of 0.6). The outstanding high-volatile mode around noontime illustrates the role of nucleation in producing more volatile particles in the summer. We further retrieve the mixing state of the ambient fine particles from the size-resolved VSF and find that the non-black carbon (BC) particles that formed from nucleation processes accounted for 52–69 % of the total number concentration in the summer. While, particles containing a refractory core that is thought to be BC-containing particles dominate and contribute 67–77 % toward the total number concentration in the winter. The diurnal cycles of the retrieved aerosol mixing state for the summer further supports the conclusion that nucleation process is the main contributors to non-BC particles. In addition, the extent of aging of BC particles was characterized as the ratio of the BC diameter before and after heating at 300 °C (Dp/Dc), showing that the average ratio of ~2.2 in the winter is higher than the average of ~1.5 in the summer, which indicates that BC aging is more efficient in wintertime, with resulting differences in light absorption enhancement between cold and warm seasons.

How many particles do we need to measure aerosol mixing state?

2020 ◽  
Author(s):  
Nicole Riemer ◽  
Jessica Gasparik ◽  
Qing Ye ◽  
Matthew West ◽  
Jeff Curtis ◽  
...  
Keyword(s):  
Sample Size ◽  
Single Particle ◽  
Measurement Techniques ◽  
Chemical Species ◽  
Finite Sample ◽  
Mixing State ◽  
Wide Range ◽  
Mixing States ◽  
The Impact ◽  
Aerosol Mixing State

<p>Atmospheric aerosols are evolving mixtures of different chemical species.  The term “aerosol mixing state” is commonly used to describe how different chemical species are distributed throughout a particle population.  A population is “fully internally mixed” if each individual particle consists of same species mixtures, whereas it is fully externally mixed if each particle only contains one species. Mixing state matters for aerosol health impacts and for climate-relevant aerosol properties, such as the particles’ propensity to form cloud droplets or the aerosol optical properties.</p><p>The mixing state metric χ quantifies the degree of internal or external mixing and can be calculated based on the particles’ species mass fractions. Several field studies have used this metric to quantify mixing states for different ambient environments using sophisticated single-particle measurement techniques. Inherent to these methods is a finite number of particles, ranging from a few hundred to several thousand particles, used to estimate the mixing state metric. </p><p>This study evaluates the error that is introduced in calculating χ due to a limited particle sample size.  We used the particle-resolved model PartMC-MOSAIC to generate a scenario library that encompasses a large number of reference particle populations and that represents a wide range of mixing states. We stochastically sub-sampled these particle populations using sample sizes of 10 to 10,000 particles and recalculated χ based on the sub-samples. This procedure mimics the impact of only having a limited sample size as it is common in real-world applications. The finite sample size leads to a consistent overestimation of χ, meaning that the populations appear more internally mixed than they are in reality. These findings are experimentally confirmed using single-particle SP-AMS measurement data from the Pittsburgh area. We also determined confidence intervals of χ for our sub-sampled populations. To determine χ within a range of  +/- 10 percentage points requires a sample size of at least 1000 particles.</p><p> </p>

scholarly journals MATRIX-VBS: implementing an evolving organic aerosol volatility in an aerosol microphysics model

2016 ◽  
Author(s):  
Chloe Y. Gao ◽  
Kostas Tsigaridis ◽  
Susanne E. Bauer
Keyword(s):  
Organic Matter ◽  
Volatile Component ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Basis Set ◽  
Oh Radicals ◽  
Mixing State ◽  
Model Framework ◽  
Organic Species ◽  
Volatile Organic

Abstract. We have implemented an existing aerosol microphysics scheme into a box model framework and extended it to represent gas-particle partitioning and chemical ageing of semi-volatile organic aerosols. We then applied this new research tool to investigate the effects of semi-volatile organic species on the growth, composition and mixing state of aerosol particles in case studies representing several different environments. The volatility-basis set (VBS) framework is implemented into the aerosol microphysical scheme MATRIX (Multiconfiguration Aerosol TRacker of mIXing state), which resolves mass and number aerosol concentrations and in multiple mixing-state classes. The new scheme, MATRIX-VBS, has the potential to significantly advance the representation of organic aerosols in Earth system models by improving upon the conventional representation as non-volatile particulate organic matter, often with also an assumed fixed size distribution. We present results from idealized cases representing Beijing, Mexico City, a Finnish and a Southeast U.S. forest, and investigate the evolution of mass concentrations and volatility distributions for organic species across the gas and particle phases, as well as assessing their mixing state among aerosol populations. Emitted semi-volatile primary organic aerosols evaporate almost completely in the high volatile range, while they remain in the particle phase in the low volatility range. Their volatility distribution depends on the applied emission factors, oxidation by OH radicals, and temperature. We also compare against parallel simulations with the original scheme, which represented only the particulate and non-volatile component of the organic aerosol, examining how differently the condensed phase organic matter is distributed across the mixing states in the model. The results demonstrate the importance of representing organic aerosol as a semi-volatile aerosol, and explicitly calculating the partitioning of organic species between the gas and particulate phases.

scholarly journals Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom

2011 ◽  
Vol 11 (17) ◽  
pp. 9037-9052 ◽  
Author(s):  
G. R. McMeeking ◽  
W. T. Morgan ◽  
M. Flynn ◽  
E. J. Highwood ◽  
K. Turnbull ◽  
...  
Keyword(s):  
Optical Properties ◽  
United Kingdom ◽  
Radiative Forcing ◽  
Organic Aerosols ◽  
Mixing State ◽  
Aerosol Composition ◽  
Air Masses ◽  
The United Kingdom ◽  
Aerosol Mass ◽  
Urban Plumes

Abstract. Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA observed in urban plumes compared to regional aerosol (0.85 versus 0.9–0.95). We attribute these differences to the presence of relatively rapidly formed secondary aerosol, primarily OOA and ammonium nitrate, which must be taken into account in radiative forcing calculations.

scholarly journals Single particle characterization using the soot particle aerosol mass spectrometer (SP-AMS)

2014 ◽  
Vol 14 (10) ◽  
pp. 15323-15361 ◽  
Author(s):  
A. K. Y. Lee ◽  
M. D. Willis ◽  
R. M. Healy ◽  
T. B. Onasch ◽  
J. P. D. Abbatt
Keyword(s):  
Mass Spectrometer ◽  
Single Particle ◽  
Soot Particle ◽  
Organic Aerosol ◽  
Anthropogenic Sources ◽  
Mixing State ◽  
Aerosol Mass Spectrometer ◽  
Mass Spectral ◽  
Aerosol Mass ◽  
The Impact

Abstract. Understanding the impact of atmospheric black carbon (BC) containing particles on human health and radiative forcing requires knowledge of the mixing state of BC, including the characteristics of the materials with which it is internally mixed. In this study, we demonstrate for the first time the capabilities of the Aerodyne Soot-Particle Aerosol Mass Spectrometer equipped with a light scattering module (LS-SP-AMS) to examine the mixing state of refractory BC (rBC) and other aerosol components in an urban environment (downtown Toronto). K-means clustering analysis was used to classify single particle mass spectra into chemically distinct groups. One resultant cluster is dominated by rBC mass spectral signals (C1+ to C5+) while the organic signals fall into a few major clusters, identified as hydrocarbon-like organic aerosol (HOA), oxygenated organic aerosol (OOA), and cooking emission organic aerosol (COA). A nearly external mixing is observed with small BC particles only thinly coated by HOA (∼28% by mass on average), while over 90% of the HOA-rich particles did not contain detectable amounts of rBC. Most of the particles classified into other inorganic and organic clusters were not significantly associated with BC. The single particle results also suggest that HOA and COA emitted from anthropogenic sources were likely major contributors to organic-rich particles with low to mid-range aerodynamic diameter (dva). The similar temporal profiles and mass spectral features of the organic clusters and the factors from a positive matrix factorization (PMF) analysis of the ensemble aerosol dataset validate the conventional interpretation of the PMF results.

scholarly journals Aerosol mixing-state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

2012 ◽  
Vol 12 (6) ◽  
pp. 15709-15742 ◽  
Author(s):  
S. Lance ◽  
T. Raatikainen ◽  
T. Onasch ◽  
D. R. Worsnop ◽  
X.-Y. Yu ◽  
...  
Keyword(s):  
Water Uptake ◽  
Early Morning ◽  
Submicron Particles ◽  
Hygroscopic Growth ◽  
Active Fraction ◽  
Mixing State ◽  
Aerosol Composition ◽  
Aerosol Mass ◽  
Time Periods ◽  
Aerosol Mixing State

Abstract. Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. κ-Köhler theory is used to evaluate the characteristic water uptake coefficient, κ*, for the CCN active aerosol population using both size-resolved HTDMA and size-resolved CCNc measurements. Organic mass fractions, forg, are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which κAMS is inferred and compared against κ*. Strong diurnal profiles of aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased κ* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN can surpass by more than a factor of two the concentrations of 100 nm particles acting as CCN, at supersaturations of 0.51% ± 0.06%. We also find that at 06:00–08:00 in the morning throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally-mixed fraction for 40 nm particles and 30% externally-mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as internally-mixed. Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning "rush hour", and the entire campaign. We show that κ* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for κ* versus particle size, which can be attributed to unresolved mixing-state and the presence of refractory material not measured by the AMS. Measured κ* typically ranges from 0.2 to 0.35, and organics typically make up 60–85% of the aerosol mass in the size range studied. Despite some disagreement between κAMS and κCCNc, we show that κAMS is able to describe CCN concentrations reasonably well, especially at the highest CCN concentrations. This is consistent with other CCN studies carried out in urban environments, and is partly due to the fact that the highest CCN concentrations occur during the daytime when the aerosol is internally-mixed and the organic fraction is relatively low. During the early morning rush hour, however, failing to account for the aerosol mixing-state often results in systematic overestimation of CCN concentrations by 50–100%.

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