scholarly journals The role of organic aerosols in homogeneous ice formation

2004 ◽  
Vol 4 (5) ◽  
pp. 6719-6745
Author(s):  
B. Kärcher ◽  
T. Koop
Keyword(s):  
Sulfuric Acid ◽  
Water Uptake ◽  
Organic Aerosols ◽  
Supercooled Liquid ◽  
Accommodation Coefficient ◽  
Model Calculations ◽  
Inorganic Particles ◽  
Organic Particles ◽  
Homogeneous Freezing ◽  
Cooling Air

Abstract. Recent field observations suggest that the fraction of organics containing aerosol particles in ice cloud particles is diminished when compared to the background aerosol prior to freezing. In this work, we use model calculations to investigate possible causes for the observed behavior. In particular, homogeneous freezing processes in cooling air parcels containing aqueous inorganic particles (represented by sulfuric acid) and organic particles (represented by pure malonic acid and mixed malonic/sulfuric acid) are studied with a detailed microphysical model. A disparate water uptake and resulting size differences that occur between organic and inorganic particles prior to freezing are identified as the most likely reason for the poor partitioning of organic aerosols into the ice phase. The differences in water uptake can be caused by changes in the relationship between solute mass fraction and water activity of the supercooled liquid phase, by modifications of the accommodation coefficient for water molecules, or by a combination thereof. The behavior of peak ice saturation ratios and total ice crystal number concentrations is examined, and the dependence of the results on cooling rate is investigated. Finally, processes are discussed that could possibly modify the homogeneous freezing behavior of organic particles.

scholarly journals The role of organic aerosols in homogeneous ice formation

2005 ◽  
Vol 5 (3) ◽  
pp. 703-714 ◽  
Author(s):  
B. Kärcher ◽  
T. Koop
Keyword(s):  
Water Uptake ◽  
Organic Aerosols ◽  
Supercooled Liquid ◽  
Accommodation Coefficient ◽  
Model Calculations ◽  
Inorganic Particles ◽  
Ice Cloud ◽  
Organic Particles ◽  
Homogeneous Freezing ◽  
Cooling Air

Abstract. Recent field observations suggest that the fraction of organic-containing aerosol particles in ice cloud particles is diminished when compared to the background aerosol prior to freezing. In this work, we use model calculations to investigate possible causes for the observed behavior. In particular, homogeneous freezing processes in cooling air parcels containing aqueous inorganic particles and organic particles are studied with a detailed microphysical model. A disparate water uptake and resulting size differences that occur between organic and inorganic particles prior to freezing are identified as the most likely reason for the poor partitioning of organic aerosols into the ice phase. The differences in water uptake can be caused by changes in the relationship between solute mass fraction and water activity of the supercooled liquid phase, by modifications of the accommodation coefficient for water molecules, or by a combination thereof. The behavior of peak ice saturation ratios and total ice crystal number concentrations is examined, and the dependence of the results on cooling rate is investigated. Finally, processes are discussed that could possibly modify the homogeneous freezing behavior of organic particles.

scholarly journals Chemical ionization of clusters formed from sulfuric acid and dimethylamine or diamines

2016 ◽  
Author(s):  
Coty N. Jen ◽  
Jun Zhao ◽  
Peter H. McMurry ◽  
David R. Hanson
Keyword(s):  
Sulfuric Acid ◽  
Chemical Ionization ◽  
Flow Reactor ◽  
Cluster Formation ◽  
Mass Spectrometers ◽  
Model Calculations ◽  
Molecule Reaction ◽  
Base Content ◽  
Atmospheric Nucleation ◽  
High Base

Abstract. Chemical ionization (CI) mass spectrometers are used to study atmospheric nucleation by detecting clusters produced by reactions of sulfuric acid and various basic gases. These instruments typically use nitrate to deprotonate and thus chemically ionize the clusters. In this study, we compare cluster concentrations measured using either nitrate or acetate. Clusters were formed in a flow reactor from vapors of sulfuric acid and dimethylamine, ethylene diamine, tetramethylethylene diamine, or butanediamine (also known as putrescine). These comparisons show that nitrate is unable to chemically ionize clusters with high base content. In addition, we vary the ion-molecule reaction time to probe ion processes which include proton-transfer, ion-molecule clustering, and decomposition of ions. Ion decomposition upon deprotonation by acetate/nitrate was observed. More studies are needed to quantify to what extent ion decomposition affects observed cluster content and concentrations, especially those chemically ionized with acetate since it deprotonates more types of clusters than nitrate. Model calculations of the neutral and ion cluster formation pathways are also presented to better identify the cluster types that are not efficiently deprotonated by nitrate. Comparison of model and measured clusters indicate that sulfuric acid dimer with two diamines and sulfuric acid trimer with two or more base molecules are not efficiently chemical ionized by nitrate. We conclude that acetate CI provides better information on cluster abundancies and their base content than nitrate CI.

scholarly journals Effects of Different Pretreatments and Seed Coat on Dormancy and Germination of Seeds of Senna obtusifolia (L.) H.S. Irwin & Barneby (Fabaceae)

2016 ◽  
Vol 8 (2) ◽  
pp. 77
Author(s):  
Stephen I. Mensah ◽  
Chimezie Ekeke
Keyword(s):  
Sulfuric Acid ◽  
Seed Dormancy ◽  
Water Uptake ◽  
Seed Coat ◽  
Critical Factor ◽  
Potassium Nitrate ◽  
Ex Situ ◽  
Mechanical Resistance ◽  
Physical Dormancy ◽  
Senna Obtusifolia

<p class="1Body">The seed dormancy of <em>Senna obtusifolia</em> was investigated through various methods, namely pretreatments in concentrated sulfuric acid, 2% potassium nitrate (KNO<sub>3</sub>), 99% ethanol, 99% methanol, and in hydrogen perioxide; examination of the seed coverings; and the determination of water uptake by the seeds in order to ascertain the most effective technique for breaking dormancy and also determine the dormancy type. The results showed that sulfuric acid treatment recorded the highest germination (100%); followed by 2% hydrogen peroxide treatment (24%) in 15minutes immersion. The methanol and ethanol pretreatments gave 18.33% and 16.5% germinations respectively. Pretreatment in 2% potassium nitrate gave the lowest germination (8.50%), while the intact seeds of <em>S. obtusifiolia</em> (control) gave 0% germination. The anatomy of the seed coat indicated the presence of hard, thickened and specialized cells of cuticle, macrosclereids, osteoscereids, and disintegrated parenchyma layers. The water uptake of intact seeds was low (13.5%) after 24 hr imbibitions. These findings revealed that the seed coat acts as barrier to germination by preventing water absorption, possibly gaseous diffusion in and out of the seed and conferring mechanical resistance to the protrusion of embryo. Pretreatments, such as immersion in H<sub>2</sub>SO<sub>4 </sub>will soften the seed coat and permit germination. Seed dormancy in <em>S. obtusifolia </em>can be considered of physical nature and classified as physical dormancy. The results obtained in this study may serve as useful information in the production and improvement of <em>S. obtusifolia </em>seedlings, as knowledge on seed dormancy and germination is a critical factor and requirements to the understanding of the propagation of this plant either in situ or ex-situ, in view of the economic potentials/attributes of this species.</p>

scholarly journals Modelling the contribution of sea salt and dimethyl sulfide derived aerosol to marine CCN

2002 ◽  
Vol 2 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Y. J. Yoon ◽  
P. Brimblecombe
Keyword(s):  
Sulfuric Acid ◽  
Dimethyl Sulfide ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Accommodation Coefficient ◽  
Sea Salt ◽  
Wind Speeds ◽  
Transfer Processes ◽  
Clean Air ◽  
The Relationship

Abstract. The concentration of cloud condensation nuclei (CCN) in the marine boundary layer (MBL) was estimated from dimethyl sulfide (DMS) flux, sea salt (SS) emission, and aerosols entrained from the free troposphere (FT). Only under clean air conditions, did the nucleation of DMS derived sulfur (DMS CCN) contribute significantly to the MBL CCN. The accommodation coefficient for sulfuric acid mass transfer was found to be a very important parameter in the modeling the contribution of DMS to MBL CCN. The relationship between seawater DMS and MBL CCN was found to be non-linear mainly due to the transfer processes of sulfuric acid onto aerosols. In addition, sea salt derived CCN (SS CCN) and entrained aerosol from the FT (FT CCN) affected the MBL CCN directly, by supplying CCN, and indirectly, by behaving as an efficient sink for sulfuric acid. The SS CCN explained more than 50% of the total predicted MBL CCN when wind speeds were moderate and high. Sea salt and FT aerosol may often be more efficient sources of MBL CCN than DMS.

Water Uptake and Optical Properties of Mixed Organic-Inorganic Particles

2021 ◽  
pp. 1-19
Author(s):  
Lucy Nandy ◽  
Yu Yao ◽  
Zhonghua Zheng ◽  
Nicole Riemer
Keyword(s):  
Optical Properties ◽  
Water Uptake ◽  
Inorganic Particles

Characterization of the temperature and humidity-dependent phase diagram of amorphous nanoscale organic aerosols

2017 ◽  
Vol 19 (9) ◽  
pp. 6532-6545 ◽  
Author(s):  
Nicholas E. Rothfuss ◽  
Markus D. Petters
Keyword(s):  
Phase Diagram ◽  
Amorphous Phase ◽  
Phase State ◽  
Organic Aerosols ◽  
State Diagram ◽  
Model Calculations ◽  
Temperature And Humidity

The amorphous phase state diagram for sucrose aerosol is obtained from a mix of measurements and model calculations.

scholarly journals Studying volatility from composition, dilution, and heating measurements of secondary organic aerosols formed during <i>α</i>-pinene ozonolysis

2018 ◽  
Vol 18 (8) ◽  
pp. 5455-5466 ◽  
Author(s):  
Kei Sato ◽  
Yuji Fujitani ◽  
Satoshi Inomata ◽  
Yu Morino ◽  
Kiyoshi Tanabe ◽  
...  
Keyword(s):  
Secondary Organic Aerosols ◽  
Yield Curve ◽  
Volume Fraction ◽  
Organic Aerosols ◽  
Accommodation Coefficient ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Mass Accommodation Coefficient ◽  
Kinetic Inhibition ◽  
Photochemical Aging

Abstract. Traditional yield curve analysis shows that semi-volatile organic compounds are a major component of secondary organic aerosols (SOAs). We investigated the volatility distribution of SOAs from α-pinene ozonolysis using positive electrospray ionization mass analysis and dilution- and heat-induced evaporation measurements. Laboratory chamber experiments were conducted on α-pinene ozonolysis, in the presence and absence of OH scavengers. Among these, we identified not only semi-volatile products, but also less volatile highly oxygenated molecules (HOMs) and dimers. Ozonolysis products were further exposed to OH radicals to check the effects of photochemical aging. HOMs were also formed during OH-initiated photochemical aging. Most HOMs that formed from ozonolysis and photochemical aging had 10 or fewer carbons. SOA particle evaporation after instantaneous dilution was measured at  < 1 and  ∼ 40 % relative humidity. The volume fraction remaining of SOAs decreased with time and the equilibration timescale was determined to be 24–46 min for SOA evaporation. The experimental results of the equilibration timescale can be explained when the mass accommodation coefficient is assumed to be 0.1, suggesting that the existence of low-volatility materials in SOAs, kinetic inhibition, or some combined effect may affect the equilibration timescale measured in this study.

Self-assembly of strawberry-like organic–inorganic hybrid particle clusters with directionally distributed bimetal and facile transformation of the core and corona

2020 ◽  
Vol 11 (18) ◽  
pp. 3136-3151 ◽  
Author(s):  
Shuxing Mei ◽  
Mingwang Pan ◽  
Juan Wang ◽  
Xiaopeng Zhang ◽  
Shaofeng Song ◽  
...  
Keyword(s):  
Strong Interaction ◽  
Self Assembly ◽  
Carboxyl Groups ◽  
Amino Groups ◽  
Inorganic Hybrid ◽  
Inorganic Particles ◽  
Hybrid Particle ◽  
The Core ◽  
Organic Particles ◽  
Facile Transformation

Controllable structure of organic–inorganic hybrid particle clusters were successfully fabricated by self-assembly which derived from the strong interaction between carboxyl groups of the organic particles and amino groups of the inorganic particles.

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