scholarly journals Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China during summertime

2015 ◽  
Vol 15 (8) ◽  
pp. 11495-11524 ◽  
Author(s):  
Z. J. Wu ◽  
J. Zheng ◽  
D. J. Shang ◽  
Z. F. Du ◽  
Y. S. Wu ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Mass Concentration ◽  
Cloud Condensation Nuclei ◽  
Empirical Relationship ◽  
Urban Atmosphere ◽  
High Time Resolution ◽  
Hygroscopic Growth ◽  
Hygroscopic Properties ◽  
Beijing China ◽  
Measurement Period

Abstract. Simultaneous measurements of particle number size distribution, particle hygroscopic properties, and size-resolved chemical composition were made during the summer of 2014 in Beijing, China. During the measurement period, the median hygroscopicity parameters (κ) of 50, 100, 150, 200, and 250 nm particles are respectively 0.15, 0.19, 0.22, 0.27, and 0.29, showing an increasing trend with increasing particle size. When PM2.5 mass concentration is greater than 50 μg m−3, the fractions of the hydrophilic mode for 150, 250, 350 nm particles increased towards 1 as PM2.5 mass concentration increased. This indicates that aged particles dominated during severe pollution periods in the atmosphere of Beijing. Particle hygroscopic growth can be well predicted using high time-resolution size-resolved chemical composition derived from AMS measurement on a basis of ZSR mixing rule. An empirical relationship between κ of organic fraction (κorg) and oxygen to carbon ratio (O : C) (κorg= 0.08·O : C+0.02) is obtained. During new particle formation event associating with strongly active photochemistry, the hygroscopic growth factor or κ of newly formed particles is greater than for particle with the same sizes during non-NPF periods. A quick transformation from external mixture to internal mixture for pre-existing particles (for example 250 nm particle) was observed. Such transformations can modify the state of mixture of pre-exiting particles and thus modify properties such as the light absorption coefficient and cloud condensation nuclei activation.

scholarly journals Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

2016 ◽  
Vol 16 (2) ◽  
pp. 1123-1138 ◽  
Author(s):  
Z. J. Wu ◽  
J. Zheng ◽  
D. J. Shang ◽  
Z. F. Du ◽  
Y. S. Wu ◽  
...  
Keyword(s):  
Particle Size ◽  
Chemical Composition ◽  
Growth Factor ◽  
Mass Concentration ◽  
Particle Formation ◽  
High Time Resolution ◽  
New Particle Formation ◽  
Hygroscopic Growth ◽  
Hygroscopic Properties ◽  
Beijing China

Abstract. Simultaneous measurements of particle number size distribution, particle hygroscopic properties, and size-resolved chemical composition were made during the summer of 2014 in Beijing, China. During the measurement period, the mean hygroscopicity parameters (κs) of 50, 100, 150, 200, and 250 nm particles were respectively 0.16  ±  0.07, 0.19  ±  0.06, 0.22  ±  0.06, 0.26  ±  0.07, and 0.28  ±  0.10, showing an increasing trend with increasing particle size. Such size dependency of particle hygroscopicity was similar to that of the inorganic mass fraction in PM1. The hydrophilic mode (hygroscopic growth factor, HGF  >  1.2) was more prominent in growth factor probability density distributions and its dominance of hydrophilic mode became more pronounced with increasing particle size. When PM2.5 mass concentration was greater than 50 μg m−3, the fractions of the hydrophilic mode for 150, 250, and 350 nm particles increased towards 1 as PM2.5 mass concentration increased. This indicates that aged particles dominated during severe pollution periods in the atmosphere of Beijing. Particle hygroscopic growth can be well predicted using high-time-resolution size-resolved chemical composition derived from aerosol mass spectrometer (AMS) measurements using the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. The organic hygroscopicity parameter (κorg) showed a positive correlation with the oxygen to carbon ratio. During the new particle formation event associated with strongly active photochemistry, the hygroscopic growth factor or κ of newly formed particles is greater than for particles with the same sizes not during new particle formation (NPF) periods. A quick transformation from external mixture to internal mixture for pre-existing particles (for example, 250 nm particles) was observed. Such transformations may modify the state of the mixture of pre-existing particles and thus modify properties such as the light absorption coefficient and cloud condensation nuclei activation.

scholarly journals Chemical composition and hygroscopic properties of aerosol particles over the Aegean Sea

2013 ◽  
Vol 13 (3) ◽  
pp. 5805-5841 ◽  
Author(s):  
S. Bezantakos ◽  
K. Barmpounis ◽  
M. Giamarelou ◽  
E. Bossioli ◽  
M. Tombrou ◽  
...  
Keyword(s):  
Growth Factors ◽  
Chemical Composition ◽  
Volume Fraction ◽  
Aegean Sea ◽  
Average Density ◽  
Back Trajectory ◽  
High Time Resolution ◽  
Hygroscopic Growth ◽  
Organic Species ◽  
Hygroscopic Properties

Abstract. The chemical composition and water uptake characteristics of sub-micrometer atmospheric particles in the region of the Aegean Sea were measured between 25 August and 11 September 2011 in the framework of the Aegean-Game campaign. High time-resolution measurements of the chemical composition of the particles were conducted using an airborne compact Time-Of-Flight Aerosol Mass Spectrometer (cTOF-AMS). These measurements involved two flights from the island of Crete to the island of Lemnos and back. A Hygroscopic Tandem Differential Mobility Analyzer (HTDMA) located on the island of Lemnos was used to measure the ability of the particles to take up water. The HTDMA measurements showed that the particles were internally mixed, having hygroscopic growth factors that ranged from 1.00 to 1.59 when exposed to 85% relative humidity. When the aircraft flew near the ground station on Lemnos, the cTOF-AMS measurements showed that the organic volume fraction of the particles ranged from 43 to 56%. These measurements corroborate the range of hygroscopic growth factors measured by the HTDMA during that time. Good closure between HTDMA and cTOF-AMS measurements was achieved when assuming that the organic species were hydrophobic and had an average density that corresponds to aged organic species. Using the results from the closure study, the cTOF-AMS measurements were employed to determine a representative aerosol hygroscopic parameter κmix for the whole path of the two flights. Calculated κmix values ranged from 0.17 to 1.03 during the first flight and from 0.15 to 0.93 during the second flight. Air masses of different origin as determined by back trajectory calculations can explain the spatial variation in the chemical composition and κmix values of the particles observed in the region.

scholarly journals Hygroscopic properties and cloud condensation nuclei activity of atmospheric aerosols under the influences of Asian continental outflow and new particle formation at a coastal site in eastern Asia

2020 ◽  
Vol 20 (10) ◽  
pp. 5911-5922 ◽  
Author(s):  
Hing Cho Cheung ◽  
Charles Chung-Kuang Chou ◽  
Celine Siu Lan Lee ◽  
Wei-Chen Kuo ◽  
Shuenn-Chin Chang
Keyword(s):  
Chemical Composition ◽  
Cloud Condensation Nuclei ◽  
Particle Formation ◽  
Number Concentration ◽  
Pollution Sources ◽  
New Particle Formation ◽  
Condensation Nuclei ◽  
Air Masses ◽  
Hygroscopic Properties ◽  
Aerosol Hygroscopicity

Abstract. The chemical composition of fine particulate matter (PM2.5), the size distribution and number concentration of aerosol particles (NCN), and the number concentration of cloud condensation nuclei (NCCN) were measured at the northern tip of Taiwan during an intensive observation experiment from April 2017 to March 2018. The parameters of aerosol hygroscopicity (i.e., activation ratio, activation diameter and kappa of CCN) were retrieved from the measurements. Significant variations were found in the hygroscopicity of aerosols (kappa – κ – of 0.18–0.56, for water vapor supersaturation – SS – of 0.12 %–0.80 %), which were subject to various pollution sources, including aged air pollutants originating in eastern and northern China and transported by the Asian continental outflows and fresh particles emitted from local sources and distributed by land–sea breeze circulations as well as produced by processes of new particle formation (NPF). Cluster analysis was applied to the back trajectories of air masses to investigate their respective source regions. The results showed that aerosols associated with Asian continental outflows were characterized by lower NCN and NCCN values and by higher kappa values of CCN, whereas higher NCN and NCCN values with lower kappa values of CCN were observed in the aerosols associated with local air masses. Besides, it was revealed that the kappa value of CCN exhibited a decrease during the early stage of an event of new particle formation, which turned to an increasing trend over the later period. The distinct features in the hygroscopicity of aerosols were found to be consistent with the characteristics in the chemical composition of PM2.5. This study has depicted a clear seasonal characteristic of hygroscopicity and CCN activity under the influence of a complex mixture of pollutants from different regional and/or local pollution sources. Nevertheless, the mixing state and chemical composition of the aerosols critically influence the aerosol hygroscopicity, and further investigations are necessary to elucidate the atmospheric processing involved in the CCN activation in coastal areas.

scholarly journals Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches

2009 ◽  
Vol 9 (12) ◽  
pp. 3999-4009 ◽  
Author(s):  
M. D. Petters ◽  
H. Wex ◽  
C. M. Carrico ◽  
E. Hallbauer ◽  
A. Massling ◽  
...  
Keyword(s):  
Water Activity ◽  
Secondary Organic Aerosol ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Water Mixture ◽  
Hygroscopic Growth ◽  
Ideal Behavior ◽  
Hygroscopic Properties ◽  
Theoretical Approaches

Abstract. We examine the hygroscopic properties of secondary organic aerosol particles generated through the reaction of α-pinene and ozone using a continuous flow reaction chamber. The water activity versus composition relationship is calculated from measurements of growth factors at relative humidities up to 99.6% and from measurements of cloud condensation nuclei activity. The observed relationships are complex, suggesting highly non-ideal behavior for aerosol water contents at relative humidities less than 98%. We present two models that may explain the observed water activity-composition relationship equally well. The first model assumes that the aerosol is a pseudo binary mixture of infinitely water soluble compounds and sparingly soluble compounds that gradually enter the solution as dilution increases. The second model is used to compute the Gibbs free energy of the aerosol-water mixture and shows that the aerosol behaves similarly to what can be expected for single compounds that contain a certain fraction of oxygenated and non-polar functional groups.

scholarly journals The influence of chemical composition and mixing state of Los Angeles urban aerosol on CCN number and cloud properties

2008 ◽  
Vol 8 (18) ◽  
pp. 5649-5667 ◽  
Author(s):  
M. J. Cubison ◽  
B. Ervens ◽  
G. Feingold ◽  
K. S. Docherty ◽  
I. M. Ulbrich ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Los Angeles ◽  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
The State ◽  
Urban Aerosol ◽  
Mixing State ◽  
Data Set ◽  
Hygroscopic Properties ◽  
Aerosol Distribution

Abstract. The relationship between cloud condensation nuclei (CCN) number and the physical and chemical properties of the atmospheric aerosol distribution is explored for a polluted urban data set from the Study of Organic Aerosols at Riverside I (SOAR-1) campaign conducted at Riverside, California, USA during summer 2005. The mixing state and, to a lesser degree, the average chemical composition are shown to be important parameters in determining the activation properties of those particles around the critical activation diameters for atmospherically-realistic supersaturation values. Closure between predictions and measurements of CCN number at several supersaturations is attempted by modeling a number of aerosol chemical composition and mixing state cases of increasing complexity. It is shown that a realistic treatment of the state of mixing of the urban aerosol distribution is critical in order to eliminate model bias. Fresh emissions such as elemental carbon and small organic particles must be treated as non-activating and explicitly accounted for in the model. The relative number concentration of these particles compared to inorganics and oxygenated organic compounds of limited hygroscopicity plays an important role in determining the CCN number. Furthermore, expanding the different composition/mixing state cases to predictions of cloud droplet number concentration in a cloud parcel model highlights the dependence of cloud optical properties on the state of mixing and hygroscopic properties of the different aerosol modes, but shows that the relative differences between the different cases are reduced compared to those from the CCN model.

scholarly journals Relating particle hygroscopicity and CCN activity to chemical composition during the HCCT-2010 field campaign

2013 ◽  
Vol 13 (16) ◽  
pp. 7983-7996 ◽  
Author(s):  
Z. J. Wu ◽  
L. Poulain ◽  
S. Henning ◽  
K. Dieckmann ◽  
W. Birmili ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Cloud Condensation Nuclei ◽  
Condensation Nucleus ◽  
Sampling Period ◽  
Cloud Condensation Nucleus ◽  
Mountain Range ◽  
Mixing Rule ◽  
Hygroscopic Growth ◽  
Parameter Values ◽  
Ccn Activity

Abstract. Particle hygroscopic growth at 90% RH (relative humidity), cloud condensation nuclei (CCN) activity, and size-resolved chemical composition were concurrently measured in the Thüringer Wald mid-level mountain range in central Germany in the fall of 2010. The median hygroscopicity parameter values, κ, of 50, 75, 100, 150, 200, and 250 nm particles derived from hygroscopicity measurements are respectively 0.14, 0.14, 0.17, 0.21, 0.24, and 0.28 during the sampling period. The closure between HTDMA (Hygroscopicity Tandem Differential Mobility Analyzers)-measured (κHTDMA) and chemical composition-derived (κchem) hygroscopicity parameters was performed based on the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. Using size-averaged chemical composition, the κ values are substantially overpredicted (30 and 40% for 150 and 100 nm particles). Introducing size-resolved chemical composition substantially improved closure. We found that the evaporation of NH4NO3, which may happen in a HTDMA system, could lead to a discrepancy in predicted and measured particle hygroscopic growth. The hygroscopic parameter of the organic fraction, κorg, is positively correlated with the O : C ratio (κorg = 0.19 × (O : C) − 0.03). Such correlation is helpful to define the κorg value in the closure study. κ derived from CCN measurement was around 30% (varied with particle diameters) higher than that determined from particle hygroscopic growth measurements (here, hydrophilic mode is considered only). This difference might be explained by the surface tension effects, solution non-ideality, gas-particle partitioning of semivolatile compounds, and the partial solubility of constituents or non-dissolved particle matter. Therefore, extrapolating from HTDMA data to properties at the point of activation should be done with great care. Finally, closure study between CCNc (cloud condensation nucleus counter)-measured (κCCN) and chemical composition (κCCN, chem) was performed using CCNc-derived κ values for individual components. The results show that the κCCN can be well predicted using particle size-resolved chemical composition and the ZSR mixing rule.

scholarly journals Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches

2008 ◽  
Vol 8 (6) ◽  
pp. 20839-20867 ◽  
Author(s):  
M. D. Petters ◽  
H. Wex ◽  
C. M. Carrico ◽  
E. Hallbauer ◽  
A. Massling ◽  
...  
Keyword(s):  
Water Activity ◽  
Secondary Organic Aerosol ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Water Mixture ◽  
Hygroscopic Growth ◽  
Ideal Behavior ◽  
Hygroscopic Properties ◽  
Theoretical Approaches

Abstract. We examine the hygroscopic properties of secondary organic aerosol particles generated through the reaction of alpha-pinene and ozone using a continuous flow reaction chamber. The water activity versus composition relationship is calculated from measurements of growth factors at relative humidities up to 99.6% and from measurements of cloud condensation nuclei activity. The observed relationships are complex, suggesting highly non-ideal behavior for aerosol water contents at relative humidities less than 98%. We present two models that may explain the observed water activity-composition relationship equally well. The first model assumes that the aerosol is a pseudo binary mixture of infinitely water soluble compounds and sparingly soluble compounds that gradually enter the solution as dilution increases. The second model is used to compute the Gibbs free energy of the aerosol-water mixture and shows that the aerosol behaves similarly to what can be expected for single compounds that contain a certain fraction of oxygenated and non-polar functional groups.

scholarly journals Hygroscopic properties and CCN activity of atmospheric aerosols under the influences of Asian continental outflow and new particle formation at a coastal site in East Asia

2019 ◽  
Author(s):  
Hing Cho Cheung ◽  
Charles C.-K. Chou ◽  
Celine S. L. Lee ◽  
Wei-Chen Kuo ◽  
Shuenn-Chin Chang
Keyword(s):  
Chemical Composition ◽  
Atmospheric Aerosols ◽  
Cloud Condensation Nuclei ◽  
Northern China ◽  
Particle Formation ◽  
Number Concentration ◽  
New Particle Formation ◽  
Air Masses ◽  
Hygroscopic Properties ◽  
Ccn Activity

Abstract. The chemical composition of fine particulate matters (PM2.5), the size distribution and number concentration of aerosol particles (NCN) and the number concentration of cloud condensation nuclei (NCCN) were measured at the northern tip of Taiwan Island during a campaign from April 2017 to March 2018. The parameters of aerosol hygroscopicity (i.e. activation ratio, activation diameter and kappa) were retrieved from the measurements. Significant variations were found in the hygroscopicity of aerosols, which were suggested be subject to various pollution sources, including aged air pollutants originating in the eastern/northern China and transported on the Asian continental outflows, fresh particles emitted from local sources and distributed by land-sea breeze circulations as well as produced by new particle formation (NPF) processes. Cluster analysis was applied to the backward trajectories of air masses to investigate their respective source regions. The results showed that the aerosols associated with Asian continental outflows were characterized with higher kappa values, whereas higher NCCN and NCN with lower kappa values were found for aerosols in local air masses. The distinct features in hygroscopicity were consistent with the characteristics in the chemical composition of PM2.5. Moreover, this study revealed that the nucleation mode particles from NPF could have participated in the enhancement of CCN activity, most likely by coagulating with sub-CCN particles, although the freshly produced particles were not favored for CCN activation due to their smaller sizes. Thus, the results of this study suggested that the NPF coupling with coagulation processes can significantly increase the NCCN in atmosphere.

scholarly journals Design and Application of an Unattended Multifunctional H-TDMA System

2013 ◽  
Vol 30 (6) ◽  
pp. 1136-1148 ◽  
Author(s):  
Haobo Tan ◽  
Hanbing Xu ◽  
Qilin Wan ◽  
Fei Li ◽  
Xuejiao Deng ◽  
...  
Keyword(s):  
Particle Size ◽  
Growth Factor ◽  
Cloud Condensation Nuclei ◽  
Polystyrene Latex ◽  
Hygroscopic Growth ◽  
Differential Mobility Analyzer ◽  
Differential Mobility ◽  
China Meteorological Administration ◽  
Hygroscopic Properties ◽  
Calibration Methods

Abstract The hygroscopic properties of aerosols have a significant impact on aerosol particle number size distributions (PNSD), formation of cloud condensation nuclei, climate forcing, and atmospheric visibility, as well as human health. To allow for the observation of the hygroscopic growth of aerosols with long-term accuracy, an unattended multifunctional hygroscopicity-tandem differential mobility analyzer (H-TDMA) system was designed and built by the Institute of Tropical and Marine Meteorology (ITMM), China Meteorological Administration (CMA), in Guangzhou, China. The system is capable of measuring dry and wet PNSD, hygroscopic growth factor by particle size, and mixing states. This article describes in detail the working principles, components, and calibration methods of the system. Standard polystyrene latex (PSL) spheres with five different diameters were chosen to test the system’s precision and accuracy of particle size measurement. Ammonium sulfate was used to test the hygroscopic response of the system for accurate growth factor measurement. The test results show that the deviation of the growth factor measured by the system is within a scope of −0.01 to −0.03 compared to Köhler theoretical curves. Results of temperature and humidity control performance tests indicate that the system is robust. An internal temperature gradient of less than 0.2 K for a second differential mobility analyzer (DMA2) makes it possible to reach a set-point relative humidity (RH) value of 90% and with a standard deviation of ±0.44%, sufficient for unattended field observation.

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