scholarly journals Viscosity and liquid–liquid phase separation in healthy and stressed plant SOA

2021 ◽  
Author(s):  
Natalie R. Smith ◽  
Giuseppe V. Crescenzo ◽  
Yuanzhou Huang ◽  
Anusha P. S. Hettiyadura ◽  
Kyla Siemens ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Phase State ◽  
Organic Aerosol ◽  
Volatile Organic ◽  
Pine Trees ◽  
Stressed Plant ◽  
Liquid Liquid Phase Separation

Molecular composition, viscosity, and phase state were investigated for secondary organic aerosol derived from synthetic mixtures of volatile organic compounds representing emissions from healthy and aphid-stressed Scots pine trees.

scholarly journals Modeling the gas-particle partitioning of secondary organic aerosol: the importance of liquid-liquid phase separation

2012 ◽  
Vol 12 (9) ◽  
pp. 3857-3882 ◽  
Author(s):  
A. Zuend ◽  
J. H. Seinfeld
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Relative Humidity ◽  
Organic Compounds ◽  
Organic Aerosol ◽  
Liquid Phase Separation ◽  
Organic Loading ◽  
Computational Costs ◽  
Ideal Mixing ◽  
Liquid Liquid Phase Separation

Abstract. The partitioning of semivolatile organic compounds between the gas phase and aerosol particles is an important source of secondary organic aerosol (SOA). Gas-particle partitioning of organic and inorganic species is influenced by the physical state and water content of aerosols, and therefore ambient relative humidity (RH), as well as temperature and organic loading levels. We introduce a novel combination of the thermodynamic models AIOMFAC (for liquid mixture non-ideality) and EVAPORATION (for pure compound vapor pressures) with oxidation product information from the Master Chemical Mechanism (MCM) for the computation of gas-particle partitioning of organic compounds and water. The presence and impact of a liquid-liquid phase separation in the condensed phase is calculated as a function of variations in relative humidity, organic loading levels, and associated changes in aerosol composition. We show that a complex system of water, ammonium sulfate, and SOA from the ozonolysis of α-pinene exhibits liquid-liquid phase separation over a wide range of relative humidities (simulated from 30% to 99% RH). Since fully coupled phase separation and gas-particle partitioning calculations are computationally expensive, several simplified model approaches are tested with regard to computational costs and accuracy of predictions compared to the benchmark calculation. It is shown that forcing a liquid one-phase aerosol with or without consideration of non-ideal mixing bears the potential for vastly incorrect partitioning predictions. Assuming an ideal mixture leads to substantial overestimation of the particulate organic mass, by more than 100% at RH values of 80% and by more than 200% at RH values of 95%. Moreover, the simplified one-phase cases stress two key points for accurate gas-particle partitioning calculations: (1) non-ideality in the condensed phase needs to be considered and (2) liquid-liquid phase separation is a consequence of considerable deviations from ideal mixing in solutions containing inorganic ions and organics that cannot be ignored. Computationally much more efficient calculations relying on the assumption of a complete organic/electrolyte phase separation below a certain RH successfully reproduce gas-particle partitioning in systems in which the average oxygen-to-carbon (O:C) ratio is lower than ~0.6, as in the case of α-pinene SOA, and bear the potential for implementation in atmospheric chemical transport models and chemistry-climate models. A full equilibrium calculation is the method of choice for accurate offline (box model) computations, where high computational costs are acceptable. Such a calculation enables the most detailed predictions of phase compositions and provides necessary information on whether assuming a complete organic/electrolyte phase separation is a good approximation for a given aerosol system. Based on the group-contribution concept of AIOMFAC and O:C ratios as a proxy for polarity and hygroscopicity of organic mixtures, the results from the α-pinene system are also discussed from a more general point of view.

scholarly journals Modeling the gas-particle partitioning of secondary organic aerosol: the importance of liquid-liquid phase separation

2012 ◽  
Vol 12 (1) ◽  
pp. 2199-2258 ◽  
Author(s):  
A. Zuend ◽  
J. H. Seinfeld
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Relative Humidity ◽  
Organic Compounds ◽  
Organic Aerosol ◽  
Liquid Phase Separation ◽  
Organic Loading ◽  
Computational Costs ◽  
Ideal Mixing ◽  
Liquid Liquid Phase Separation

Abstract. The partitioning of semivolatile organic compounds between the gas phase and aerosol particles is an important source of secondary organic aerosol (SOA). Gas-particle partitioning of organic and inorganic species is influenced by the physical state and water content of aerosols, and therefore ambient relative humidity (RH), as well as temperature and organic loading levels. We introduce a novel combination of the thermodynamic models AIOMFAC (for liquid mixture non-ideality) and EVAPORATION (for pure compound vapor pressures) with oxidation product information from the Master Chemical Mechanism (MCM) for the computation of gas-particle partitioning of organic compounds and water. The presence and impact of a liquid-liquid phase separation in the condensed phase is calculated as a function of variations in relative humidity, organic loading levels, and associated changes in aerosol composition. We show that a complex system of water, ammonium sulfate, and SOA from the ozonolysis of α-pinene exhibits liquid-liquid phase separation over a wide range of relative humidities (simulated from 30% to 99% RH). Since fully coupled phase separation and gas-particle partitioning calculations are computationally expensive, different simplified model approaches are tested with regards to computational costs and accuracy of predictions compared to the benchmark calculation. Both forcing a liquid one-phase aerosol considering non-ideal mixing or assuming an ideal mixture bear the potential for vastly incorrect partitioning predictions. Assuming an ideal mixture leads to substantial overestimation of the particulate organic mass, at high RH by more than 200%. Moreover, the simplified one-phase cases stress two key points for accurate gas-particle partitioning calculations: (1) non-ideality in the condensed phase needs to be considered and (2) liquid-liquid phase separation is a consequence of considerable deviations from ideal mixing in solutions containing inorganic ions and organics that cannot be ignored. Computationally much more efficient calculations relying on the assumption of a complete organic/electrolyte phase separation below a certain RH successfully reproduce gas-particle partitioning in systems in which the average oxygen-to-carbon (O:C) ratio is lower than ~0.6, as in the case of α-pinene SOA, and bear the potential for implementation in atmospheric chemical transport models and chemistry-climate models. A full equilibrium calculation is the method of choice for accurate offline (box model) computations, where high computational costs are acceptable. Such a calculation enables the most detailed predictions of phase compositions and provides necessary information on whether assuming a complete organic/electrolyte phase separation is a good approximation for a given aerosol system. Based on the group-contribution concept of AIOMFAC and O:C ratios as a proxy for polarity and hygroscopicity of organic mixtures, the results from the α-pinene system are also discussed from a more general point of view.

Phase separation in organic aerosol

2017 ◽  
Vol 46 (24) ◽  
pp. 7694-7705 ◽  
Author(s):  
Miriam Arak Freedman
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Organic Compounds ◽  
Aerosol Particles ◽  
Organic Aerosol ◽  
Liquid Phase Separation ◽  
Climate Effects ◽  
Liquid Liquid Phase Separation

Liquid–liquid phase separation is prevalent in aerosol particles composed of organic compounds and salts and may impact aerosol climate effects.

scholarly journals Liquid–liquid phase separation in organic particles consisting of α-pinene and β-caryophyllene ozonolysis products and mixtures with commercially-available organic compounds

2020 ◽  
Author(s):  
Young-Chul Song ◽  
Ariana G. Bé ◽  
Scot T. Martin ◽  
Franz M. Geiger ◽  
Allan K. Bertram ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Organic Compounds ◽  
Spinodal Decomposition ◽  
Aerosol Particles ◽  
Organic Aerosol ◽  
Liquid Phases ◽  
Two Component ◽  
Organic Particles ◽  
Liquid Liquid Phase Separation

Abstract. Liquid–liquid phase separation (LLPS) in organic aerosol particles can impact several properties of atmospheric particulate matter, such as cloud condensation nuclei (CCN) properties, optical properties, and gas-to-particle partitioning. Yet, our understanding of LLPS in organic aerosols is far from complete. Here, we report on LLPS of one-component and two-component organic particles consisting of α-pinene- and β-caryophyllene-derived ozonolysis products and commercially-available organic compounds of relevance to atmospheric organic particles. In the experiments involving single-component organic particles, LLPS was observed in 8 out of 11 particle types studied. LLPS almost always occurred when the oxygen-to-carbon elemental ratio (O : C) was ≤ 0.44, but did not occur when O : C was > 0.44. The phase separation occurred by spinodal decomposition, and when LLPS occurred, two liquid phases co-existed up to ~ 100 % relative humidity (RH). In the experiments involving two-component organic particles, LLPS was observed in 23 out of 25 particles types studied. LLPS almost always occurred when the average was O : C ≤ 0.67, but never occurred when the average O : C was > 0.67. The phase separation occurred by spinodal decomposition or growth of a second phase at the surface of the particles. When LLPS occurred, two liquid phases co-existed up to ~ 100 %. These results provide further evidence that LLPS is likely a frequent occurrence in organic aerosol particles in the troposphere, even in the absence of inorganic salts.

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 Modeling organic aerosol concentrations and properties during winter 2014 in the northwestern Mediterranean region

2018 ◽  
Author(s):  
Mounir Chrit ◽  
Karine Sartelet ◽  
Jean Sciare ◽  
Marwa Majdi ◽  
José Nicolas ◽  
...  
Keyword(s):  
Air Quality ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Oxidation State ◽  
Organic Aerosol ◽  
Single Step ◽  
Basis Set ◽  
Residential Heating ◽  
Volatile Organic ◽  
Northwestern Mediterranean

Abstract. Organic aerosols are measured at a remote site (Ersa) on Corsica Cape in the northwestern Mediterranean basin during the Chemistry-Aerosol Mediterranean Experiment (CharMEx) winter campaign of 2014, when high organic concentrations from anthropogenic origin are observed. This work aims at representing the observed organic aerosol concentrations and properties (oxidation state) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Because intermediate/semi-volatile organic compounds (I/S-VOC) are the main precursors of SOA at Ersa during the winter 2014, different parameterizations to represent the emission and ageing of I/S-VOC were implemented in the chemistry-transport model of the air-quality platform Polyphemus (different volatility distribution emissions, single-step oxidation vs multi-step oxidation within a Volatility Basis Set framework, inclusion of non-traditional volatile organic compounds NTVOC). Simulations using the different parameterizations are compared to each other and to the measurements (concentration and oxidation state). The high observed organic concentrations are well reproduced whatever the parameterizations. They are slightly under-estimated with most parameterizations, but they are slightly over-estimated when the ageing of NTVOC is taken into account. The volatility distribution at emissions influences more strongly the concentrations than the choice of the parameterization that may be used for ageing (single-step oxidation vs multi-step oxidation), stressing the importance of an accurate characterization of emissions. Assuming the volatility distribution of sectors other than residential heating to be the same as residential heating may lead to a strong under-estimation of organic concentrations. The observed organic oxidation and oxygenation states are strongly under-estimated in all simulations, even when a recently developed parameterization for modeling the ageing of I/S-VOC from residential heating is used. This suggests that uncertainties in the ageing of I/S-VOC emissions remain to be elucidated, with a potential role of organic nitrate from anthropogenic precursors and highly oxygenated organic molecules.

scholarly journals Secondary organic aerosol enhanced by increasing atmospheric oxidizing capacity in Beijing–Tianjin–Hebei (BTH), China

2019 ◽  
Vol 19 (11) ◽  
pp. 7429-7443 ◽  
Author(s):  
Tian Feng ◽  
Shuyu Zhao ◽  
Naifang Bei ◽  
Jiarui Wu ◽  
Suixin Liu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Secondary Organic Aerosol ◽  
Action Plan ◽  
Spatial Relationship ◽  
Pollution Prevention ◽  
Organic Aerosol ◽  
Temporal Variations ◽  
Volatile Organic

Abstract. The implementation of the Air Pollution Prevention and Control Action Plan in China since 2013 has profoundly altered the ambient pollutants in the Beijing–Tianjin–Hebei (BTH) region. Here we show observations of substantially increased O3 concentrations (about 30 %) and a remarkable increase in the ratio of organic carbon (OC) to elemental carbon (EC) in BTH during the autumn from 2013 to 2015, revealing an enhancement in atmospheric oxidizing capacity (AOC) and secondary organic aerosol (SOA) formation. To explore the impacts of increasing AOC on the SOA formation, a severe air pollution episode from 3 to 8 October 2015 with high O3 and PM2.5 concentrations is simulated using the WRF-Chem model. The model performs reasonably well in simulating the spatial distributions of PM2.5 and O3 concentrations over BTH and the temporal variations in PM2.5, O3, NO2, OC, and EC concentrations in Beijing compared to measurements. Sensitivity studies show that the change in AOC substantially influences the SOA formation in BTH. A sensitivity case characterized by a 31 % O3 decrease (or 36 % OH decrease) reduces the SOA level by about 30 % and the SOA fraction in total organic aerosol by 17 % (from 0.52 to 0.43, dimensionless). Spatially, the SOA decrease caused by reduced AOC is ubiquitous in BTH, but the spatial relationship between SOA concentrations and the AOC is dependent on the SOA precursor distribution. Studies on SOA formation pathways further show that when the AOC is reduced, the SOA from oxidation and partitioning of semivolatile primary organic aerosol (POA) and co-emitted intermediate volatile organic compounds (IVOCs) decreases remarkably, followed by those from anthropogenic and biogenic volatile organic compounds (VOCs). Meanwhile, the SOA decrease in the irreversible uptake of glyoxal and methylglyoxal on the aerosol surfaces is negligible.

scholarly journals Liquid-liquid phase separation and viscosity within secondary organic aerosol generated from diesel fuel vapors

2019 ◽  
Author(s):  
Mijung Song ◽  
Adrian M. Maclean ◽  
Yuanzhou Huang ◽  
Natalie R. Smith ◽  
Sandra L. Blair ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Diesel Fuel ◽  
Diffusion Coefficients ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Liquid Phase Separation ◽  
Small Diffusion ◽  
Wide Range ◽  
Liquid Liquid Phase Separation

Abstract. Information on liquid-liquid phase separation (LLPS) and viscosity (or diffusion) within secondary organic aerosol (SOA) is needed to improve predictions of particle size, mass, reactivity, and cloud nucleating properties in the atmosphere. Here we report on LLPS and viscosities within SOA generated by the photooxidation of diesel fuel vapors. Diesel fuel contains a wide range of volatile organic compounds, and SOA generated by the photooxidation of diesel fuel vapors may be a good proxy for SOA from anthropogenic emissions. In our experiments, LLPS occurred over the relative humidity (RH) range of ~ 70 % to ~ 100 %, resulting in an organic-rich outer phase and a water-rich inner phase. These results may have implications for predicting the cloud nucleating properties of anthropogenic SOA since the organic-rich outer phase can lower the kinetic barrier for activation to a cloud droplet. At ≤ 10 % RH, the viscosity was in the range of ≥ 1 × 108 Pa s, which corresponds to roughly the viscosity of tar pitch. At 38–50 % RH the viscosity was in the range of 1 × 108–3 × 105 Pa s. These measured viscosities are consistent with predictions based on oxygen to carbon elemental ratio (O : C) and molar mass as well as predictions based on the number of carbon, hydrogen, and oxygen atoms. Based on the measured viscosities and the Stokes–Einstein relation, at ≤ 10 % RH diffusion coefficients of organics within diesel fuel SOA is ≤ 5.4 × 10−17cm2 s−1 and the mixing time of organics within 200 nm diesel fuel SOA particles (τmixing) is ≳ 50 h. These small diffusion coefficients and large mixing times may be important in laboratory experiments, where SOA is often generated and studied using low RH conditions and on time scales of minutes to hours. At 38–50 % RH, the calculated organic diffusion coefficients are in the range of 5.4 × 10−17 to 1.8 × 10−13 cm2 s−1 and calculated τmixing values are in the range of ~ 0.01 h to ~ 50 h. These values provide important constraints for the physicochemical properties of anthropogenic SOA.

Sign in / Sign up

Export Citation Format

Share Document