scholarly journals A simple representation of surface active organic aerosol in cloud droplet formation

2011 ◽  
Vol 11 (9) ◽  
pp. 4073-4083 ◽  
Author(s):  
N. L. Prisle ◽  
M. Dal Maso ◽  
H. Kokkola
Keyword(s):  
Atmospheric Aerosols ◽  
Cloud Droplet ◽  
Organic Aerosol ◽  
Droplet Formation ◽  
Cloud Microphysics ◽  
Aerosol Composition ◽  
Detailed Model ◽  
Simple Representation ◽  
Model Predictions ◽  
Surface Active

Abstract. Atmospheric aerosols often contain surface active organics. Surface activity can affect cloud droplet formation through both surface partitioning and surface tension reduction in activating droplets. However, a comprehensive thermodynamic account for these effects in Köhler modeling is computationally demanding and requires knowledge of both droplet composition and component molecular properties, which is generally unavailable. Here, a simple representation of activation properties for surface active organics is introduced and compared against detailed model predictions and laboratory measurements of CCN activity for mixed surfactant-salt particles from the literature. This simple organic representation is seen to work well for aerosol organic-inorganic composition ranges typically found in the atmosphere, and agreement with both experiments and detailed model predictions increases with surfactant strength. The simple representation does not require resolution of the organic aerosol composition and relies solely on properties of the organic fraction that can be measured directly with available techniques. It can thus potentially be applied to complex and ambient surface active aerosols. It is not computationally demanding, and therefore has high potential for implementation to atmospheric models accounting for cloud microphysics.

scholarly journals A simple representation of surface active organic aerosol in cloud droplet formation

2010 ◽  
Vol 10 (10) ◽  
pp. 23601-23625
Author(s):  
N. L. Prisle ◽  
M. Dal Maso ◽  
H. Kokkola
Keyword(s):  
Atmospheric Aerosols ◽  
Cloud Droplet ◽  
Organic Aerosol ◽  
Droplet Formation ◽  
Cloud Microphysics ◽  
Aerosol Composition ◽  
Detailed Model ◽  
Simple Representation ◽  
Model Predictions ◽  
Surface Active

Abstract. Atmospheric aerosols often contain surface active organics. Surface activity can affect cloud droplet formation through both surface partitioning and surface tension reduction in activating droplets. However, a comprehensive thermodynamic account for these effects in Köhler modeling is computationally demanding and requires knowledge of both droplet composition and component molecular properties, which is generally unavailable. Here, a simple representation of activation properties for surface active organics is introduced and compared against detailed model predictions and laboratory measurements of CCN activity for mixed surfactant-salt particles from the literature. This simple organic representation is seen to work well for aerosol organic-inorganic composition ranges typically found in the atmosphere, and agreement with both experiments and detailed model predictions increases with surfactant strength. The simple representation does not require resolution of the organic aerosol composition and relies solely on properties of the organic fraction that can be measured directly with available techniques. Thus, it has high potential for application to complex and ambient aerosol. It is not computationally demanding, and therefore also has potential for implementation to atmospheric models accounting for cloud microphysics.

scholarly journals Regional influence of wildfires on aerosol chemistry in the western US and insights into atmospheric aging of biomass burning organic aerosol

2017 ◽  
Vol 17 (3) ◽  
pp. 2477-2493 ◽  
Author(s):  
Shan Zhou ◽  
Sonya Collier ◽  
Daniel A. Jaffe ◽  
Nicole L. Briggs ◽  
Jonathan Hee ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Chemical Transformation ◽  
Biomass Burning ◽  
Atmospheric Aerosols ◽  
Global Climate ◽  
Organic Aerosol ◽  
The United States ◽  
Aerosol Composition ◽  
Western Us ◽  
The Impact

Abstract. Biomass burning (BB) is one of the most important contributors to atmospheric aerosols on a global scale, and wildfires are a large source of emissions that impact regional air quality and global climate. As part of the Biomass Burning Observation Project (BBOP) field campaign in summer 2013, we deployed a high-resolution time-of-flight aerosol mass spectrometer (HR-AMS) coupled with a thermodenuder at the Mt. Bachelor Observatory (MBO, ∼  2.8 km above sea level) to characterize the impact of wildfire emissions on aerosol loading and properties in the Pacific Northwest region of the United States. MBO represents a remote background site in the western US, and it is frequently influenced by transported wildfire plumes during summer. Very clean conditions were observed at this site during periods without BB influence where the 5 min average (±1σ) concentration of non-refractory submicron aerosols (NR-PM1) was 3.7 ± 4.2 µg m−3. Aerosol concentration increased substantially (reaching up to 210 µg m−3 of NR-PM1) for periods impacted by transported BB plumes, and aerosol composition was overwhelmingly organic. Based on positive matrix factorization (PMF) of the HR-AMS data, three types of BB organic aerosol (BBOA) were identified, including a fresh, semivolatile BBOA-1 (O ∕ C  =  0.35; 20 % of OA mass) that correlated well with ammonium nitrate; an intermediately oxidized BBOA-2 (O ∕ C  =  0.60; 17 % of OA mass); and a highly oxidized BBOA-3 (O ∕ C  =  1.06; 31 % of OA mass) that showed very low volatility with only  ∼  40 % mass loss at 200 °C. The remaining 32 % of the OA mass was attributed to a boundary layer (BL) oxygenated OA (BL-OOA; O ∕ C  =  0.69) representing OA influenced by BL dynamics and a low-volatility oxygenated OA (LV-OOA; O ∕ C  =  1.09) representing regional aerosols in the free troposphere. The mass spectrum of BBOA-3 resembled that of LV-OOA and had negligible contributions from the HR-AMS BB tracer ions – C2H4O2+ (m∕z = 60.021) and C3H5O2+ (m∕z = 73.029); nevertheless, it was unambiguously related to wildfire emissions. This finding highlights the possibility that the influence of BB emission could be underestimated in regional air masses where highly oxidized BBOA (e.g., BBOA-3) might be a significant aerosol component but where primary BBOA tracers, such as levoglucosan, are depleted. We also examined OA chemical evolution for persistent BB plume events originating from a single fire source and found that longer solar radiation led to higher mass fraction of the chemically aged BBOA-2 and BBOA-3 and more oxidized aerosol. However, an analysis of the enhancement ratios of OA relative to CO (ΔOA ∕ΔCO) showed little difference between BB plumes transported primarily at night versus during the day, despite evidence of substantial chemical transformation in OA induced by photooxidation. These results indicate negligible net OA production in photochemically aged wildfire plumes observed in this study, for which a possible reason is that SOA formation was almost entirely balanced by BBOA volatilization. Nevertheless, the formation and chemical transformation of BBOA during atmospheric transport can significantly influence downwind sites with important implications for health and climate.

scholarly journals Regional Influence of Wildfires on Aerosol Chemistry in the Western US and Insights into Atmospheric Aging of Biomass Burning Organic Aerosol

2016 ◽  
Author(s):  
Shan Zhou ◽  
Sonya Collier ◽  
Daniel A. Jaffe ◽  
Nicole L. Briggs ◽  
Jonathan Hee ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Biomass Burning ◽  
Atmospheric Aerosols ◽  
Global Climate ◽  
Organic Aerosol ◽  
The United States ◽  
Global Scale ◽  
Aerosol Composition ◽  
Photo Oxidation ◽  
The Impact

Abstract. Biomass burning (BB) is one of the most important contributors to atmospheric aerosols on a global scale and wildfires are a large source of emissions that impact regional air quality and global climate. As part of the Biomass Burning Observation Project (BBOP) field campaign in summer 2013, we deployed a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-AMS) coupled with a thermodenuder at the Mt. Bachelor Observatory (MBO, ~ 2.8 km above sea level) to characterize the impact of wildfire emissions on aerosol loading and properties in the Pacific Northwest region of the United States. MBO represents a remote background site in the western U.S. and it is frequently influenced by transported wildfire plumes during summer. Very clean conditions were observed at this site during periods without BB influence where the 5-min average (±1σ) concentration of non-refractory submicron aerosols (NR-PM1) was 3.7 ± 4.2 μg m−3. Aerosol concentration increased substantially (reaching up to 210 µg m−3 of NR-PM1) for periods impacted by transported BB plumes and aerosol composition was overwhelmingly organic. Based on Positive Matrix Factorization (PMF) of the HR-AMS data, three types of BB organic aerosol (BBOA) were identified, including a fresh, semivolatile BBOA-1 (O/C = 0.35; 20 % of OA mass) that correlated well with ammonium nitrate, an intermediately oxidized BBOA-2 (O/C = 0.60; 17 % of OA mass), and a highly oxidized BBOA-3 (O/C = 1.06; 31 % of OA mass) that showed very low volatility with only ~ 40 % mass loss at 200 °C. The remaining 32 % of the organic aerosol (OA) mass was attributed to a boundary layer (BL) OOA (BL-OOA; O/C = 0.69) representing OA influenced by BL dynamics and a low-volatility oxygenated OA (LV-OOA; O/C = 1.09) representing regional free troposphere aerosol. The mass spectrum of BBOA-3 resembled that of LV-OOA and had negligible contributions from the HR-AMS BB tracer ions – C2H4O2+ (m/z = 60.021) and C3H5O2+ (m/z = 73.029). This finding highlights the possibility that the influence of BB emission could be underestimated in regional air masses where highly oxidized BBOA (e.g. BBOA-3) might be a significant aerosol component. We also examined OA chemical evolution for persistent BB plume events originating from a single fire source and found that longer solar radiation led to higher mass fraction of the chemically aged BBOA-2 and BBOA-3 and more oxidized aerosol. However, an analysis of the enhancement ratios of OA relative to CO (ΔOA/ΔCO) showed little difference between BB plumes transported primarily at night versus during the day, despite evidence of substantial chemical transformation in OA induced by photo-oxidation. These results indicate negligible net OA production with photo-oxidation for wildfire plumes observed in this study, for which a possible reason is that SOA formation was almost entirely balanced by BBOA volatilization.

The role of surface active molecules in cloud droplet formation

2009 ◽  
Vol 6 (28) ◽  
pp. 282024
Author(s):  
Noenne Lvng Prisle ◽  
T Raatikainen ◽  
A Laaksonen ◽  
M Bilde
Keyword(s):  
Cloud Droplet ◽  
Droplet Formation ◽  
Surface Active

scholarly journals Indirect Impact of Atmospheric Aerosols in Idealized Simulations of Convective–Radiative Quasi Equilibrium. Part II: Double-Moment Microphysics

2011 ◽  
Vol 24 (7) ◽  
pp. 1897-1912 ◽  
Author(s):  
Wojciech W. Grabowski ◽  
Hugh Morrison
Keyword(s):  
Atmospheric Aerosols ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Bowen Ratio ◽  
Cloud Microphysics ◽  
Quasi Equilibrium ◽  
Double Moment ◽  
The Mean ◽  
The Difference ◽  
The Impact

Abstract This paper extends the previous cloud-resolving modeling study concerning the impact of cloud microphysics on convective–radiative quasi equilibrium (CRQE) over a surface with fixed characteristics and prescribed solar input, both mimicking the mean conditions on earth. The current study applies sophisticated double-moment warm-rain and ice microphysics schemes, which allow for a significantly more realistic representation of the impact of aerosols on precipitation processes and on the coupling between clouds and radiative transfer. Two contrasting cloud condensation nuclei (CCN) characteristics are assumed, representing pristine and polluted conditions, as well as contrasting representations of the effects of entrainment and mixing on the mean cloud droplet size. In addition, four sets of sensitivity simulations are also performed with changes that provide a reference for the main simulation set. As in the previous study, the CRQE mimics the estimates of globally and annually averaged water and energy fluxes across the earth’s atmosphere. There are some differences from the previous study, however, consistent with the slightly lower water vapor content in the troposphere and significantly reduced lower-tropospheric cloud fraction in current simulations. There is also a significant reduction of the difference between the pristine and polluted cases, from ∼20 to ∼4 W m−2 at the surface from ∼20 to ∼9 W m−2 at the top of the atmosphere (TOA). The difference between the homogeneous and extremely inhomogeneous mixing scenarios, ∼20 W m−2 in the previous study, is reduced to a mere 2 (1) W m−2 at the surface (TOA). An unexpected difference between the previous and current simulations is the lower Bowen ratio of the surface heat flux, the partitioning of the total flux into sensible and latent components. It is shown that most of the change comes from the difference in the representation of rain evaporation in the subcloud layer in the single- and double-moment microphysics schemes. The difference affects the mean air temperature and humidity near the surface, and thus the Bowen ratio. The differences between the various simulations are discussed, contrasting the process-level approach with the impact of cloud microphysics on the quasi-equilibrium state with a more appropriate system dynamics approach. The key distinction is that the latter includes the interactions among all the processes in the modeled system.

scholarly journals Droplet activation of moderately surface active organic aerosol predicted with six approaches to surface activity

2021 ◽  
Author(s):  
Sampo Vepsäläinen ◽  
Silvia M. Calderón ◽  
Jussi Malila ◽  
Nønne L. Prisle
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Surface Activity ◽  
Atmospheric Aerosols ◽  
Cloud Microphysics ◽  
Organic Mass ◽  
Surface Partitioning ◽  
Mass Fractions ◽  
Surface Active ◽  
Droplet Activation

Abstract. Surface active compounds (surfactants) found in atmospheric aerosols can decrease droplet surface tension as they adsorb to the droplet surfaces simultaneously depleting the droplet bulk. These processes may influence the activation properties of aerosols into cloud droplets and investigation of their role in cloud microphysics has been ongoing for decades. In this study, we have used six different approaches documented in the literature to represent surface activity in Köhler calculations predicting cloud droplet activation properties for particles consisting of one of three different moderately surface active organics mixed with ammonium sulphate in different ratios. We find that the different models predict comparable activation properties at small organic mass fractions in the dry particles for all three moderately surface active organics tested, even with large differences in the predicted degree of bulk-to-surface partitioning of the surface active component. However, differences between the models regarding both the predicted critical diameter and supersaturation for the same dry particle size increase with the organic fraction in the particles. Comparison with available experimental data shows that assuming complete bulk-to-surface partitioning of the organic component (total depletion of the bulk) along the full droplet growth curve does not adequately represent the activation properties of particles with high moderate surfactant mass fractions. Accounting for the surface tension depression mitigates some of the effect. Models that include the possibility for partial bulk-to-surface partitioning yield comparable results to the experimental data, even at high organic mass fractions in the particles. The study highlights the need for using thermodynamically consistent model frameworks to treat surface activity of atmospheric aerosols and for firm experimental validation of model predictions across a wide range of states relevant to the atmosphere.

Size-Resolved Surface-Active Substances of Atmospheric Aerosol: Reconsideration of the Impact on Cloud Droplet Formation

2018 ◽  
Vol 52 (16) ◽  
pp. 9179-9187 ◽  
Author(s):  
Ana Kroflič ◽  
Sanja Frka ◽  
Martin Simmel ◽  
Heike Wex ◽  
Irena Grgić
Keyword(s):  
Atmospheric Aerosol ◽  
Cloud Droplet ◽  
Droplet Formation ◽  
Surface Active ◽  
The Impact ◽  
Active Substances

scholarly journals Aging of atmospheric aerosols and the role of iron in catalyzing brown carbon formation

2021 ◽  
Author(s):  
Hind A. A. Al-Abadleh
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Atmospheric Aerosols ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Atmospheric Oxidation ◽  
Carbon Formation ◽  
Brown Carbon ◽  
Volatile Organic

Extensive research has been done on the processes that lead to the formation of secondary organic aerosol (SOA) including atmospheric oxidation of volatile organic compounds (VOCs) from biogenic and anthropogenic...

scholarly journals Large contribution to secondary organic aerosol from isoprene cloud chemistry

2021 ◽  
Vol 7 (13) ◽  
pp. eabe2952
Author(s):  
Houssni Lamkaddam ◽  
Josef Dommen ◽  
Ananth Ranjithkumar ◽  
Hamish Gordon ◽  
Günther Wehrle ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Cloud Droplet ◽  
Organic Aerosol ◽  
Global Scale ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Large Contribution ◽  
Cloud Processing

Aerosols still present the largest uncertainty in estimating anthropogenic radiative forcing. Cloud processing is potentially important for secondary organic aerosol (SOA) formation, a major aerosol component: however, laboratory experiments fail to mimic this process under atmospherically relevant conditions. We developed a wetted-wall flow reactor to simulate aqueous-phase processing of isoprene oxidation products (iOP) in cloud droplets. We find that 50 to 70% (in moles) of iOP partition into the aqueous cloud phase, where they rapidly react with OH radicals, producing SOA with a molar yield of 0.45 after cloud droplet evaporation. Integrating our experimental results into a global model, we show that clouds effectively boost the amount of SOA. We conclude that, on a global scale, cloud processing of iOP produces 6.9 Tg of SOA per year or approximately 20% of the total biogenic SOA burden and is the main source of SOA in the mid-troposphere (4 to 6 km).

scholarly journals Urban organic aerosol composition in Eastern China differs from North to South: Molecular insight from a liquid chromatography-Orbitrap mass spectrometry study

2019 ◽  
Author(s):  
Kai Wang ◽  
Ru-Jin Huang ◽  
Martin Brüggemann ◽  
Yun Zhang ◽  
Lu Yang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Eastern China ◽  
Organic Aerosol ◽  
Photochemical Oxidation ◽  
Lower Latitude ◽  
Molecular Formula ◽  
Aerosol Composition ◽  
Orbitrap Mass Spectrometry ◽  
Low Degrees

Abstract. Particulate air pollution in China is influencing human health, ecosystem and climate. However, the chemical composition of particulate aerosol, especially of the organic fraction, is still not well understood. In this study, particulate aerosol samples with a diameter ≤ 2.5 μm (PM2.5) were collected in January 2014 in three cities located in Northeast, East and Southeast China, i.e., Changchun, Shanghai and Guangzhou, respectively. Organic aerosol (OA) in the PM2.5 samples was analyzed by ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution Orbitrap mass spectrometry in both negative mode (ESI−) and positive mode electrospray ionization (ESI+). After a non-target screening including molecular formula assignments, compounds were classified into five groups based on their elemental composition, i.e., CHO, CHON, CHN, CHOS and CHONS. The CHO, CHON and CHN compounds present the dominant signal abundances of 81–99.7 % in the mass spectra and the majority of these compounds were assigned to mono- and polyaromatics, suggesting that anthropogenic emissions are a large source of urban OA in all three cities. However, the chemical characteristics of these compounds varied among different cities. The degree of aromaticity and the number of polyaromatic compounds were significantly higher in samples from Changchun, which could be attributed to the large emissions from residential heating (i.e., coal combustion) during winter time in Northeast China. Moreover, the ESI− analysis showed higher H / C and O / C ratios for organic compounds in Shanghai and Guangzhou compared to samples from Changchun, indicating that OA in lower latitude regions of China experiences more intense photochemical oxidation processes. The majority of sulfur-containing compounds (CHOS and CHONS) in all cities were assigned to aliphatic compounds with low degrees of unsaturation and aromaticity. Again, samples from Shanghai and Guangzhou exhibit a larger chemical similarity but largely differ from those from Changchun.

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