scholarly journals Hygroscopicity of aerosol particles and CCN activity of nearly hydrophobic particles in the urban atmosphere over Japan during summer

2016 ◽  
Vol 121 (12) ◽  
pp. 7215-7234 ◽  
Author(s):  
Shuhei Ogawa ◽  
Yoshitaka Setoguchi ◽  
Kaori Kawana ◽  
Tomoki Nakayama ◽  
Yuka Ikeda ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Urban Atmosphere ◽  
Hydrophobic Particles ◽  
Ccn Activity

Rapid measurement of particle hygroscopicity and CCN activity using broad scanning supersaturation (BS2)-CCNC: calibration and intercomparison

2021 ◽  
Author(s):  
Najin Kim ◽  
Yafang Cheng ◽  
Nan Ma ◽  
Mira Pöhlker ◽  
Thomas Klimach ◽  
...  
Keyword(s):  
Particle Size ◽  
Time Resolution ◽  
Calibration Curve ◽  
Aerosol Particles ◽  
High Time ◽  
Activity Measurement ◽  
High Time Resolution ◽  
Chemical Compositions ◽  
Monotonic Relation ◽  
Ccn Activity

<p>For understanding and assessing aerosol-cloud interactions and their impact on climate, reliable measurement data of aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity are required. Furthermore, aerosol liquid water, mainly controlled by hygroscopicity, affects heterogeneous and multiphase reactions of aerosol particles. The CCN activity of aerosol particles can be determined by scanning particle size and supersaturation (S) in the CCN measurement. Compared to the existing CCN activity measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of S simultaneously, can measure particle hygroscopicity and CCN activity with a high-time resolution. Based on a monotonic relation between the activation supersaturation of aerosol particles (S<sub>aerosol</sub>)  and the activation fraction (F<sub>act</sub>) of the BS2-CCN measurement, we can derive κ, a single hygroscopicity parameter, directly.</p><p>Here, we describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve (F<sub>act</sub> - S<sub>aerosol</sub>). For calibration, size-resolved CCN measurements with ammonium sulfate (AS) and sodium chloride particles are performed under the three different thermal gradient (dT) conditions (dT=6, 8, and 10). First, the shape of the calibration curve is primarily influenced by S<sub>max</sub>, maximum S in the activation tube. We need to determine appropriate S<sub>max</sub> depending on particle size and κ to be investigated. To minimize the effect of double/multiple charged particles, small  D<sub>g </sub>and σ<sub>g</sub>  in number size distribution are recommended when generating the calibration aerosols. Sheath-to-aerosol-flow ratio (SAR) is the third factor to be considered. BS2-CCNC system uses a low SAR with a wider inlet compared to the typical CCN measurement, which can make a monotonic relation between F<sub>act</sub> and S<sub>aerosol</sub>. Lastly, F<sub>act </sub>is affected by particle number concentration and has a decreasing rate of 0.02/100 cm<sup>-3</sup> (within N<sub>CN</sub> ~ 300 cm<sup>-3</sup> for AS) due to the water consumption in the chamber. For evaluating the BS2-CCN system, inter-comparison experiments between typical DMA-CCN and BS2-CCN measurement were performed with the laboratory-generated aerosol mixture and ambient aerosols. Statistically good agreements of κ values between DMA-CCN and BS2-CCN measurements for both inter-comparison experiments imply that the BS2-CCN system can measure particle hygroscopicity and CCN activity well compared to the existing measurement. We expect that this new system can be applied to aircraft and ship measurements that require a high-time resolution as well as ground measurement for a broad range of hygroscopicity distribution. Because hygroscopicity is closely related to the fraction of organics/inorganics in aerosol particles, our method can also serve as a complementary approach for fast detection/estimation of aerosol chemical compositions. </p>

scholarly journals Morphological, chemical and optical absorbing characterization of aerosols in the urban atmosphere of Valladolid

2005 ◽  
Vol 5 (10) ◽  
pp. 2739-2748 ◽  
Author(s):  
S. Mogo ◽  
V. E. Cachorro ◽  
A. M. de Frutos
Keyword(s):  
Mass Fraction ◽  
Fine Particles ◽  
Aerosol Particles ◽  
Cascade Impactor ◽  
Urban Atmosphere ◽  
Coarse Particles ◽  
X Ray ◽  
Illumination System ◽  
Inverse Power Law

Abstract. Samples of atmospheric aerosol particles were collected in Valladolid, Spain, during the winter of 2003-2004. The measurements were made with a Dekati PM10 cascade impactor with four size stages: greater than 10 µm, between 2.5 to 10 µm, 1 to 2.5 µm and less than 1 µm. The size and shape of the particles were analyzed with a scanning electron microscope (SEM) and elemental analysis was done with an energy dispersive x-ray analysis (EDX). We present an evaluation by size, shape and composition of the major particulate species in the Valladolid urban atmosphere. The total aerosol concentration is very variable, ranging from 39.86 µg·m-3 to 184.88 µg·m-3 with the coarse particles as the dominant mass fraction. Emphasis was given to fine particles (<1 µm), for which the visible (400 nm to 650 nm) light absorption coefficients were measured using the integrating plate technique. We have made some enhancements in the illumination system of this measurement system. The absorption coefficient, σa, is highly variable and ranges from 7.33×10-6 m-1 to 1.01×10-4 m-1 at a wavelength of 550 nm. There is an inverse power law relationship between σa and wavelength, with an average exponent of -0.8.

scholarly journals Spatio-temporal variability and principal components of the particle number size distribution in an urban atmosphere

2009 ◽  
Vol 9 (9) ◽  
pp. 3163-3195 ◽  
Author(s):  
F. Costabile ◽  
W. Birmili ◽  
S. Klose ◽  
T. Tuch ◽  
B. Wehner ◽  
...  
Keyword(s):  
Size Distribution ◽  
Particle Number ◽  
Aerosol Particles ◽  
Urban Traffic ◽  
Urban Atmosphere ◽  
Urban Aerosol ◽  
Number Size Distribution ◽  
Spatio Temporal ◽  
20 Nm ◽  
Aitken Mode

Abstract. A correct description of fine (diameter <1 μm) and ultrafine (<0.1 μm) aerosol particles in urban areas is of interest for particle exposure assessment but also basic atmospheric research. We examined the spatio-temporal variability of atmospheric aerosol particles (size range 3–800 nm) using concurrent number size distribution measurements at a maximum of eight observation sites in and around Leipzig, a city in Central Europe. Two main experiments were conducted with different time span and number of observation sites (2 years at 3 sites; 1 month at 8 sites). A general observation was that the particle number size distribution varied in time and space in a complex fashion as a result of interaction between local and far-range sources, and the meteorological conditions. To identify statistically independent factors in the urban aerosol, different runs of principal component (PC) analysis were conducted encompassing aerosol, gas phase, and meteorological parameters from the multiple sites. Several of the resulting PCs, outstanding with respect to their temporal persistence and spatial coverage, could be associated with aerosol particle modes: a first accumulation mode ("droplet mode", 300–800 nm), considered to be the result of liquid phase processes and far-range transport; a second accumulation mode (centered around diameters 90–250 nm), considered to result from primary emissions as well as aging through condensation and coagulation; an Aitken mode (30–200 nm) linked to urban traffic emissions in addition to an urban and a rural Aitken mode; a nucleation mode (5–20 nm) linked to urban traffic emissions; nucleation modes (3–20 nm) linked to photochemically induced particle formation; an aged nucleation mode (10–50 nm). Additional PCs represented only local sources at a single site, or infrequent phenomena. In summary, the analysis of size distributions of high time and size resolution yielded a surprising wealth of statistical aerosol components occurring in the urban atmosphere over one single city. A paradigm on the behaviour of sub-μm urban aerosol particles is proposed, with recommendations how to efficiently monitor individual sub-fractions across an entire city.

scholarly journals Spatio-temporal variability and principal components of the particle number size distribution in an urban atmosphere

2008 ◽  
Vol 8 (5) ◽  
pp. 18155-18217 ◽  
Author(s):  
F. Costabile ◽  
W. Birmili ◽  
S. Klose ◽  
T. Tuch ◽  
B. Wehner ◽  
...  
Keyword(s):  
Particle Number ◽  
Aerosol Particles ◽  
Urban Traffic ◽  
Urban Atmosphere ◽  
Urban Aerosol ◽  
Size Distributions ◽  
Spatial Coverage ◽  
Temporal Persistence ◽  
Spatio Temporal ◽  
20 Nm

Abstract. Due to the presence of diffusive anthropogenic sources in urban areas, the spatio-temporal variability of fine (diameter <1 μm) and ultrafine (<0.1 μm) aerosol particles has been a challenging issue in particle exposure assessment as well as atmospheric research in general. We examined number size distributions of atmospheric aerosol particles (size range 3–800 nm) that were measured simultaneously at a maximum of eight observation sites in and around a city in Central Europe (Leipzig, Germany). Two main experiments were conducted with different time span and number of observation sites (2 years at 3 sites; 1 month at 8 sites). A general observation was that the particle number size distribution varied in time and space in a complex fashion as a result of interaction between local and far-range sources, and the meteorological conditions. To identify statistically independent factors in the urban aerosol, different runs of principal component analysis were conducted encompassing aerosol, gas phase, and meteorological parameters from the multiple sites. Several of the resulting principal components, outstanding with respect to their temporal persistence and spatial coverage, could be associated with aerosol particle modes: a first accumulation mode ("droplet mode", 300–800 nm), considered to be the result of liquid phase processes and far-range transport; a second accumulation mode (centered around diameters 90–250 nm), considered to result from primary emissions as well as aging through condensation and coagulation; an Aitken mode (30–200 nm) linked to urban traffic emissions in addition to an urban and a rural Aitken mode; a nucleation mode (5–20 nm) linked to urban traffic emissions; nucleation modes (3–20 nm) linked to photochemically induced particle formation; an aged nucleation mode (10–50 nm). A number of additional components were identified to represent only local sources at a single site each, or infrequent phenomena. In summary, the analysis of size distributions of high time and size resolution yielded a surprising wealth of statistical aerosol components occurring in the urban atmosphere over one single city. Meanwhile, satisfactory physical explanations could be found for the components with the greatest temporal persistence and spatial coverage. Therefore a paradigm on the behaviour of sub-μm urban aerosol particles is proposed, with recommendations how to efficiently monitor individual sub-fractions across an entire city.

scholarly journals Evaluation of the contribution of new particle formation to cloud droplet in urban atmosphere

2021 ◽  
Author(s):  
Sihui Jiang ◽  
Fang Zhang ◽  
Jingye Ren ◽  
Lu Chen ◽  
Xing Yan ◽  
...  
Keyword(s):  
Water Vapor ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Cloud Droplet ◽  
Particle Formation ◽  
Urban Atmosphere ◽  
Primary Sources ◽  
New Particle Formation ◽  
Multiple Sources ◽  
Considerable Impact

Abstract. New particle formation (NPF) is a large source of cloud condensation nuclei (CCN) and cloud droplet in the troposphere. In this study, we quantified the contribution of NPF to cloud droplet number concentration (CDNC, or Nd) at typical updraft velocities (V) in clouds using a field campaign data of aerosol number size distribution and chemical composition observed on May 25–June 18, 2017 in urban Beijing. We show that the NPF drives the variations of CCN and cloud droplet and increases Nd by 30–33 % at V = 0.3–3 m s−1 in urban atmosphere. A markedly reduction in Nd is observed due to water vapor competition with consideration of actual environmental updraft velocity, decreasing by 11.8 ± 5.0 % at V = 3 m s−1 and 19.0 ± 4.5 % at V = 0.3 m s−1 compared to that from a prescribed supersaturation. The effect of water vapor competition becomes smaller at larger V that can provide more sufficient water vapor. Essentially, water vapor competition led to the reduction in Nd by decreasing the environmental maximum supersaturation (Smax) for the activation of aerosol particles. It is shown that Smax was decreased by 14.5–11.7 % for V = 0.3–3 m s−1. Particularly, the largest suppression of cloud droplet formation due to the water vapor competition is presented at extremely high aerosol particle number concentrations. As a result, although a larger increase of CCN-size particles by NPF event is derived on clean NPF day when pre-existing background aerosol particles are very low, there is no large discrepancy in the enhancement of Nd by NPF between the clean and polluted NPF day. We finally show a considerable impact of the primary sources when evaluating the NPF contribution to cloud droplet based on a case study. Our study highlights the importance of fully consideration of both the environmental meteorological conditions and multiple sources (i.e. secondary and primary) to evaluate the NPF effect on clouds and the associated climate effects in polluted regions.

Characteristics of PM2.5 aerosol particles during a heat wave in an urban atmosphere in southwest Germany

2020 ◽  
Author(s):  
Junwei Song ◽  
Linyu Gao ◽  
Harald Saathoff
Keyword(s):  
Black Carbon ◽  
Heat Wave ◽  
Mass Spectrometer ◽  
Heat Waves ◽  
Aerosol Particles ◽  
Organic Aerosol ◽  
Urban Atmosphere ◽  
Ionization Mass ◽  
Aerosol Compositions ◽  
Southwest Germany

&lt;p&gt;Aerosol particles have significant impacts on climate, air quality, and human health. Their characteristics are especially important in urban atmospheres during heat waves. Therefore, we conducted a 4-week measurement campaign at an urban kerbside in the city of Karlsruhe in southwest Germany during a heat wave period in July 2019. A high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed in the container to measure non-refractory aerosol compositions of PM&lt;sub&gt;2.5&lt;/sub&gt; online. Filter samples were also collected during the campaign, and characterized for oxygenated organic molecular compounds using a chemical ionization mass spectrometer (FIGAERO-CIMS). In addition, a small box with low cost particle sensors and meteorological sensors (solar radiation, temperature, and humidity) was used for spatial resolved measurements employing a bicycle. During our measurement, the total organics, sulfate, nitrate, ammonium, chloride and black carbon contributed on average 58.9%, 17.3%, 5.9%, 5.5%, 0.2% and 12.3% to the particle mass comprising non-refractory components plus black carbon. Positive matrix factorization (PMF) analysis for the AMS organic aerosol (OA) data resolved three factors including hydrocarbon-like OA (HOA), semi-volatile oxygenated OA (SV-OOA) and low-volatility oxygenated OA (LV-OOA). Meteorological effects on aerosol compositions were investigated. Low wind speeds during the whole campaign correspond to major contributions from local emissions. During heat waves, high temperature and low humidity suppressed the formation of nitrate, but facilitated the formation of sulfate and organics. In particular, SV-OOA and LV-OOA showed positive correlations with temperature. The ratios of LV-OOA to SV-OOA strongly correlated with temperature and odd oxygen (O&lt;sub&gt;x&lt;/sub&gt; = O&lt;sub&gt;3&lt;/sub&gt; + NO&lt;sub&gt;2&lt;/sub&gt;), suggesting fast photochemical transformation of SV-OOA to LV-OOA during heat waves. Furthermore, the relationships between organic aerosol factors and typical organic markers were investigated to study the relative influences of biogenic and anthropogenic emissions on OA formation. Besides, bicycle measurements point to important hot spots of particle pollution. This contribution will discuss the interaction of urban air pollution and heat islands.&lt;/p&gt;

scholarly journals Dependence of the hygroscopicity parameter κ on particle size, humidity and solute concentration: implications for laboratory experiments, field measurements and model studies

2017 ◽  
Author(s):  
Zhibin Wang ◽  
Yafang Cheng ◽  
Nan Ma ◽  
Eugene Mikhailov ◽  
Ulrich Pöschl ◽  
...  
Keyword(s):  
Particle Size ◽  
Water Vapor ◽  
Chemical Composition ◽  
Laboratory Experiments ◽  
Aerosol Particles ◽  
Strong Dependence ◽  
Solute Concentration ◽  
Individual Species ◽  
Activity Measurements ◽  
Ccn Activity

Abstract. The hygroscopicity parameter κ has been intensively used in the investigation of the water uptake, cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosol particles. A representative value of κ is often assigned to individual species or sources. Such treatment may lead to confusion in closure studies of κ derived from hygroscopic growth factor measurements (κgf) and CCN activity measurements (κCCN), and in studies of aerosols at the sub-10 nm size range. Here we show that for particles of the same dry composition, κ may differ as a function of water content, solute concentration and particle size. The concentration- and size-dependence of κ are demonstrated for representative inorganic and organic compounds, i.e., ammonium sulfate (AS), sodium chloride (NaCl) and sucrose. Our results illustrate that an absolute closure between κgf and κCCN should not be expected, and how the deviations observed in field and laboratory experiments can be quantitatively explained and reconciled. The difference between κgf and κCCN increases as particle size decreases reaching up to 40 % and 30 % for 10 nm AS and NaCl particles, respectively. Moreover, we show that the deviations of κCCN vary from ~ 10 % for 30 nm and ~ 40 % for 200 nm, indicating a strong dependence on the Köhler models and thermodynamic parameterizations used for instrument calibration (e.g., effective water vapor supersaturation in CCN counter). By taking these factors into account, we can largely explain apparent discrepancies between κgf and κCCN values reported in the scientific literature. Our results help to understand and interpret κ values determined at different water vapor ratios and at different size ranges (especially sub-10 nm). We highlight the importance of self-consistent thermodynamic parameterizations when using AS for calibration aerosol and taking it as a reference substance representing inorganics in closure study between chemical composition and hygroscopicity of aerosol particles.

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