Size Distribution Of Atmospheric Particles Research Articles

Ambient particulate pollution during Chinese Spring Festival in urban Lanzhou, Northwestern China

The effect of firework displays on ambient particulate pollution in a typical valley city in Northwestern China was evaluated based on high temporal resolution atmospheric particle size distribution (10–10 000nm) data and particle mass concentrations in different sizes obtained during 25th January – 24th February, 2013. Firework displays have significant impact on particle number concentrations in accumulation mode (100–1 000nm), especially in 200–500nm, as well as PM1 mass concentrations. The hourly mean number concentration in 200–500 nm and PM1 mass concentration during the peak hour of firework displays were 11 800.2±2 548.0cm–3 and 214.1±31.2μg m−3, which are approximately 6 times and 2 times of that before the festival, respectively, with a maximum10–min mean number concentration in size range 100–1 000 nm reaching 3.8×104cm−3 on the New Year's Eve (00:10 BT 10th February, 2013). It was estimated that local emissions and firework displays contributed 74.6% and 37.0%, respectively, to the number concentration of particles less than 1 000nm. On short–time scale, the contribution of firework displays on local particulate pollution is obvious and should not be ignored, especially on fine particulate pollution.

Effect of traffic restriction on atmospheric particle concentrations and their size distributions in urban Lanzhou, Northwestern China

During the 2012 Lanzhou International Marathon, the local government made a significant effort to improve traffic conditions and air quality by implementing traffic restriction measures. To evaluate the direct effect of these measures on urban air quality, especially particle concentrations and their size distributions, atmospheric particle size distributions (0.5–20 μm) obtained using an aerodynamic particle sizer (model 3321, TSI, USA) in June 2012 were analyzed. It was found that the particle number, surface area and volume concentrations for size range 0.5–10 μm were (15.0±2.1) cm−3, (11.8±2.6) μm2/cm3 and (1.9±0.6) μm2/cm3, respectively, on the traffic-restricted day (Sunday), which is 63.2%, 53.0% and 47.2% lower than those on a normal Sunday. For number and surface area concentrations, the most affected size range was 0.5–0.7 and 0.5–0.8 μm, respectively, while for volume concentration, the most affected size ranges were 0.5–0.8, 1.7–2.0 and 5.0–5.4 μm. Number and volume concentrations of particles in size range 0.5–1.0 μm correlated well with the number of non–CNG (Compressed Natural Gas) powered vehicles, while their correlation with the number of CNG-powered vehicles was very low, suggesting that reasonable urban traffic controls along with vehicle technology improvements could play an important role in improving urban air quality.

STUDY ON THE RELATIONSHIP OF VISIBILITY AND AEROSOL CHARACTERISTICS IN TAIPEI

In an urban environment, visibility strongly reflects human safety and welfare. Generally, visibility is dependent on particle scattering and absorption. The former is influenced by light wavelength, atmospheric gaseous species and particle characteristics, especially number and size distribution. Therefore, it is necessary to establish the relationship between visibility and particle characteristics. Furthermore, it is important to understand the formation mechanism of secondary aerosols. In this study, a micro-orifice uniform deposit impactor (MOUDI) was used to measure the particle size distribution. At the same time, the particle scattering coefficient was measured with a nephelometer. After sampling, the chemical compositions of the particulates were analyzed via ion chromatography (IC) and a total organic carbon (TOC) analyzer. The results show that coarse particulates are not related to the scattering coefficient, whereas the scattering coefficient is slightly relative to the fine particle mass concentration. From the measured scattering coefficient, the visibility was calculated to be in the range of 20,000 to 120,000 m. The predicted visibility is greater than the observed data, ranging from 18,000 to 100,000 m at the Song-Sun Airport.

Seasonal differences of the atmospheric particle size distribution in a metropolitan area in Japan

We compared the effect of ambient temperature observed in two different seasons on the size distribution and particle number concentration (PNC) as a function of distance (up to ~250m) from a major traffic road (25% of the vehicles are heavy-duty diesel vehicles). The modal particle diameter was found between 10 and 30nm at the roadside in the winter. However, there was no peak for this size range in the summer, even at the roadside. Ambient temperature affects both the atmospheric dilution ratio (DR) and the evaporation rate of particles, thus it affects the decay rate of PNC. We corrected the DR effect in order to focus on the effect of particle evaporation on PNC decay. The decay rate of PNC with DR was found to depend on the season and particle diameter. During the winter, the decay rate for smaller particles (<30nm) was much higher (i.e., the concentration decreased significantly against DR), whereas it was low during the summer. In contrast, for particles >30nm in diameter, the decay rate was nearly the same during both seasons. This distinction between particles less than or greater than 30nm in diameter reflects differences in particle volatility properties. Mass-transfer theory was used to estimate evaporation rates of C20–C36 n-alkane particles, which are the major n-alkanes in diesel exhaust particles. The C20–C28 n-alkanes of 30-nm particles completely evaporate at 31.2°C (summer), and their lifetime is shorter than the transport time of air masses in our region of interest. Absence of the peak at 10–30nm and the low decay rate of PNC <30nm in diameter in the summer were likely due to the evaporation of compounds of similar volatilities comparable to the C20–C36 n-alkanes from particles near the exhaust pipes of vehicles, and complete evaporation of semivolatile materials before they reached the roadside. These results suggest that the lifetime of particles <30nm in diameter depends on the ambient temperature, which differs between seasons. This leads us to conclude that these particles show distinctly different spatial distributions depending on the season.

Dynamic state of the atmosphere in aerosol components

An approach to analyzing experimental data on the size distribution and concentrations of atmospheric aerosol particles and meteorological parameters by using the flicker-noise spectroscopy is proposed. This approach makes it possible to identify the character of evolution of the measured parameters due to the processes underlying their variation, to trace the relationship between measured quantities, and, based on this, to determine the mechanisms of interactions between aerosol particles and gaseous components of the atmosphere. As an example, the behavior of the concentration, average particle size, and relative humidity of the atmosphere is examined. Atmospheric measurements were carried out at the recreation center in Tishkovo (Moscow Region). The proposed approach may prove useful in solving ecological and environmental problems.

Nucleation and Aitken mode atmospheric particles in relation to O3 and NOX at semirural background in Denmark

Abstract Atmospheric oxidants (O3, NO and NO2) and particle size distributions (6–700 nm) were studied at a semi-rural background location in Denmark during 2009 to evaluate the sources of particulate matter. Aitken mode particles (30–110 nm) and accumulation mode particles (110–700 nm) anti-correlated or showed no correlation with O3. The lower Aitken mode (

Relating atmospheric and oceanic DMS levels to particle nucleation events in the Canadian Arctic

[1] Measurements of ocean surface and atmospheric dimethyl sulfide (DMS) and particle size distributions were made in the Canadian Arctic Archipelago during the fall of 2007 and the late summer of 2008 aboard the Canadian Coast Guard Ship Amundsen. Nucleation-mode particles were observed during the 2008 cruise, which took place in the eastern Arctic from August to September when the atmosphere and ocean were more photo-active as compared to the October 2007 transit in the Beaufort Sea during which no nucleation/growth events were observed. The observed nucleation periods in 2008 coincided with high atmospheric and ocean surface DMS concentrations, suggesting that the particles originated from marine biogenic sources. An aerosol microphysics box model was used to simulate nucleation given the measured conditions in the marine boundary layer. Although other sources may have contributed, we find that the newly formed particles can be accounted for by a marine biogenic DMS source for combinations of the following parameters: [OH] ≥ 3 × 105 molecules cm−3, DMS mixing ratio is ≥ 100 pptv, the activation coefficient is ≤ 10−7 and the background particle concentration is ≤ 100 cm−3.

Single-Particle Characterization of Atmospheric Aerosols Collected at Gosan, Korea, during the Asian Pacific Regional Aerosol Characterization Experiment Field Campaign Using Low-Z (Atomic Number) Particle Electron Probe X-ray Microanalysis

ABSTRACT A quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), namely low-Z (atomic number) particle EPMA, was used to characterize the chemical compositions of the individual aerosol particles collected at the Gosan supersite, Jeju Island, Korea, as a part of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia). On 4–10 April 2001 just before a severe dust storm arrived, seven sets of aerosol samples were obtained by a seven-stage May cascade impactor with a flow rate of 20 L/min. Overall 11,200 particles on stages 1–6 with cutoff diameters of 16, 8, 4, 2, 1, and 0.5 μm, respectively, were examined and classified based on their secondary electron images and X-ray spectra. In general, sea salt particles were the most frequently encountered, followed by mineral dust, organic carbon (OC)-like, (NH4)2SO4/NH4HSO4-containing, elemental carbon (EC)-like, Fe-rich, and K-rich particles. Sea salt and mineral dust particles had a higher relative abundance on stages 1–5, whereas OC-like, (NH4)2SO4/NH4HSO4-containing, Fe-rich, and K-rich particles were relatively abundant on stage 6. The analysis on relative number abundances of various particle types combined with 72-hr backward air mass trajectories indicated that a lot of reacted sea salt and reacted mineral dust (with airborne NOx and SO2 or their acidic products) and OC-like particles were carried by the air masses passing over the Yellow Sea (for sample “10 April”) and many NH4HSO4/(NH4)2SO4-containing particles were carried by the air masses passing over the Sea of Japan and Korea Strait (for samples “4–9 April”). It was concluded that the atmosphere over Jeju Island was influenced by anthropogenic SO2 and NOx, organic compounds, and secondary aerosols when Asian dust was absent. IMPLICATIONS A quantitative energy-dispersive electron probe X-ray microanalysis, called low-Z particle EPMA, was used to characterize aerosol particles collected at Jeju Island, Korea, on 4–10 April of 2001 during the intensive observation period of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The particle size distribution and chemical compositions of individual atmospheric particles over Jeju Island were obtained, and many environmentally important atmospheric particles containing sulfate, nitrate, sea salt, alminosilicate, and carbonaceous species in the size range of 0.5–16 μm were characterized. It was found that anthropogenic SO2 and NOx made great impacts on compositions of aerosol particles. The results helped better understand how air pollutants interacted with aerosol particles in the Asia-Pacific region.

Weighted Flow Algorithms (WFA) for stochastic particle coagulation

Stochastic particle-resolved methods are a useful way to compute the time evolution of the multi-dimensional size distribution of atmospheric aerosol particles. An effective approach to improve the efficiency of such models is the use of weighted computational particles. Here we introduce particle weighting functions that are power laws in particle size to the recently-developed particle-resolved model PartMC-MOSAIC and present the mathematical formalism of these Weighted Flow Algorithms (WFA) for particle coagulation and growth. We apply this to an urban plume scenario that simulates a particle population undergoing emission of different particle types, dilution, coagulation and aerosol chemistry along a Lagrangian trajectory. We quantify the performance of the Weighted Flow Algorithm for number and mass-based quantities of relevance for atmospheric sciences applications.

Improved Normalization of the Size Distribution of Atmospheric Particles Retrieved from Aureole Measurements Using the Diffraction Approximation

Abstract This paper describes an improvement in the diffraction approximation used to retrieve the size distribution of atmospheric particles from solar aureole radiance measurements. Normalization using total optical thickness based on measurement of the solar disk radiance is replaced with one based on the aureole profile radiance itself. Retrievals involving model calculations for power-law distributions of water droplets show significant improvement using the new algorithm. Tests involving two empirical particle size distributions, one for cirrus and another for aerosols, also show improvement using the new normalization algorithm. Comparisons of the diffraction approximation algorithms with a numerical inversion algorithm found that the accuracy of the latter was higher for two different bimodal aerosol distributions. The role envisioned for the diffraction approximation is in estimating the size distribution of large particles in clouds and especially cirrus.

The ion–aerosol interactions from the ion mobility and aerosol particle size distribution measurements on January 17 and February 18, 2005 at Maitri, Antarctica – A case study

A case study for the ion–aerosol interactions is presented from the simultaneous measurements of mobility spectra of atmospheric ions in the mobility range of 2.29 to 2.98 × 10 − 4 cm2 V − 1 s $^{-1}$ (diameter range 0.41–109 nm) and of size distribution of atmospheric aerosol particles in the size ranges of 4.4–700 nm and 500–20,000 nm diameters made at Maitri (70°45′52′ ′S, 11°44′2.7′ ′E; 130 m above mean sea level), Antarctica, on two days January 17 and February 18, 2005, with contrasting meteorological conditions. In contrast to January 17, on February 18, winds were stronger from the morning to noon and lower from the noon to evening, atmospheric pressure was lower, cloudiness was more, the land surface remained snow-covered after a blizzard on February 16 and 17 and the airmass over Maitri, descended from an altitude of ~3 km after an excursion over ocean. On these days mobility spectra showed two modes, corresponding to intermediate ions and light large ions and an indication of additional one/two maxima for small/cluster ions and heavy large ions. The small ions generated by cosmic rays, and the nucleation mode particles generated probably by photochemical reactions grew in size by condensation of volatile trace gases on them and produced the cluster and intermediate ion modes and the Aitken particle mode in ion/particle spectra. Particles in the size range of 9–26 nm have been estimated to grow at the rate of 1.9 nm h − 1 on February 18, 2005. Both, ions and aerosol particles show bimodal size distributions in the 16–107 nm size range, and comparison of the two size distributions suggests the formation of multiple charged ions. Attachment of small ions to particles in this bimodal distribution of Aitken particles together with the formation of multiple charged ions are proposed to result in the light and heavy large ion modes. Growth of the nucleation mode particles on February 18, 2005 is associated with the passage of the airmass over ocean. In contrast, though the ion size distributions were not much different, the aerosol size distributions did not show a dominant peak for the formation and growth of nucleation mode particles on January 17. More measurements are needed before the conclusion of this case study is generalized.

The Modified Gamma Size Distribution Applied to Inhomogeneous and Nonspherical Particles: Key Relationships and Conversions

Abstract The four-parameter modified gamma distribution (MGD) is the most general mathematically convenient model for size distributions of particle types ranging from aerosols and cloud droplets or ice particles to liquid and frozen precipitation. The common three-parameter gamma distribution, the exponential distribution (e.g., Marshall–Palmer), and power-law distribution (e.g., Junge) are all special cases. Depending on the context, the particle “size” used in a given formulation may be the actual geometric diameter, the volume- or area-equivalent spherical diameter, the actual or equivalent radius, the projected or surface area, or the mass. For microphysical and radiative transfer calculations, it is often necessary to convert from one size representation to another, especially when comparing or utilizing distribution parameters obtained from a variety of sources. Furthermore, when the mass scales with Db, with b &amp;lt; 3, as is typical for snow and ice and other particles having a quasi-fractal structure, an exponential or gamma distribution expressed in terms of one size parameter becomes an MGD when expressed in terms of another. The MGD model is therefore more fundamentally relevant to size distributions of nonspherical particles than is often appreciated. The central purpose of this paper is to serve as a concise single-source reference for the mathematical properties of, and conversions between, atmospheric particle size distributions that can expressed as MGDs, including exponential and gamma distributions as special cases. For illustrative purposes, snow particle size distributions published by Sekhon and Srivastava, Braham, and Field et al. are converted to a common representation and directly compared for identical snow water content, allowing large differences in their properties to be discerned and quantified in a way that is not as easily achieved without such conversion.

The Truncated Geometric Approximation and the Size Distribution of Small Atmospheric Particles

Abstract This paper describes a simple relationship between the slope of particulate optical depth as a function of wavelength and the size distribution of spherical particles. It is based on approximating extinction using a truncated geometric optics relationship and is applicable when optical depth decreases with wavelength. The new relationship suggests that extinction versus wavelength measurements are most sensitive to particles that are comparable in size to the wavelength. When optical depth is expressed as a power-law function of wavelength, the resulting particle size distribution is also a power-law function of size, with the two exponents reproducing the well-known relationship between the Ångström and Junge exponents. Examples of applying the new relationship are shown using both numerical calculations based on Mie theory and measurements from the Aerosol Robotic Network (AERONET) sun photometer at NASA Goddard Space Flight Center (GSFC). Since the truncated geometric approximation makes no assumptions per se concerning the form of the particle size distribution, it may find application in supplementing solar aureole profile measurements in retrieving the size distributions of particles in thin clouds—for example, cirrus—or when they are present.

Size Distribution and Elemental Characteristics of Atmospheric Particles during Winter in Harbin

In order to investigate the characteristic of atmospheric particles, TSP, PM10 and PM2.5 were collected in winter and non-winter. This study investigates the size distribution and elemental characteristics of atmospheric particles. The results show that PM2.5 makes a great contribution to TSP, which changes with the concentration of TSP. PM2.5/ PM10 specially reaches the highest value, increased from 53.5% to 87.2%. It can indicate that the main pollution sources are fine particles from man-made pollution. Others, PM2.5/TSP and TSP are not strictly proportional relationship. The concentration of the elements in TSP is higher than in PM2.5, which are primarily present in coarse particles. While the contribution of S is the highest among them, in particular the contribution of S in PM2.5 reaches 33.8%. This is mainly due to coal-fired in winter, and fine particulate accounts for large percentage in coal dust.

An Enhanced Procedure for the Merging of Atmospheric Particle Size Distribution Data Measured Using Electrical Mobility and Time-of-Flight Analysers

Current merging algorithms for particle size spectral data collected with electrical mobility and aerodynamic time-of-flight instruments either require a priori knowledge of densities and shape factors, or use alignment of the number spectra alone to determine an optimal fit and effective density. In this work, an enhanced algorithm is described in which the best fit between the two instrument datasets is achieved for the number, surface area, and volume spectra, also yielding estimated values of transition-regime effective density. When applied to data collected at a kerbside site, integrated aerosol mass calculated from the merged data correlates highly with independently measured PM10 mass data. Typical merged data from the site are shown and used to examine the diurnal and wind direction dependence of the estimated values of transition-regime effective density derived from the merging procedure.

Deposition velocity of ultrafine particles measured with the Eddy‐Correlation Method over the Nansen Ice Sheet (Antarctica)

This work reports an analysis of the concentration, size distribution, and deposition velocity of atmospheric particles over snow and iced surfaces on the Nansen Ice Sheet (Antarctica). Measurements were performed using the eddy‐correlation method at a remote site during the XXII Italian expedition of the National Research Program in Antarctica (PNRA) in 2006. The measurement system was based on a condensation particle counter (CPC) able to measure particles down to 9 nm in diameter with a 50% efficiency and a Differential Mobility Particle Sizer for evaluating particle size distributions from 11 to 521 nm diameter in 39 channels. A method based on postprocessing with digital filters was developed to take into account the effect of the slow time response of the CPC. The average number concentration was 1338 cm−3 (median, 978 cm−3; interquartile range, 435–1854 cm−3). Higher concentrations were observed at low wind velocities. Results gave an average deposition velocity of 0.47 mm/s (median, 0.19 mm/s; interquartile range, −0.21 −0.88 mm/s). Deposition increased with the friction velocity and was on average 0.86 mm/s during katabatic wind characterized by velocities higher than 4 m/s. Observed size distributions generally presented two distinct modes, the first at approximately 15–20 nm and the second (representing on average 70% of the total particles) at 60–70 nm. Under strong‐wind conditions, the second mode dominated the average size distribution.

Particle Size Distribution of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in the Ambient Air of an Electric-Arc Furnace-Dust Treatment Plant

Atmospheric particle size distributions of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) between 0.166 and 100 μm in aerodynamic diameter (Dp) were measured at two sampling sites. The two sites (OR and SG) were approximately 100 m from the fugitive emission areas inside an electric-arc furnace-dust treatment plant (hereinafter to referred as the TSU plant) and were 6.5 and 1.5 m above ground level, respectively. Size-segregated atmospheric particles were collected through means of a micro-orifice uniform deposit impactor (MOUDI) and a Noll rotary impactor (NRI) when the sampling sites were downwind (April, 2007) and upwind (May, 2007) from the fugitive emission area of the TSU plant. Experimental results indicate that PCDD/Fs were associated with the full size range of atmospheric particles. For fugitive sources in TSU plant, although less than 49% of total PCDD/Fs and toxic equivalents (TEQs) were found to be associated with fine particles, more than 54% of total PCDD/Fs and TEQs were correlated with fine particles from outside-plant emission sources. Particle size distributions of total PCDD/Fs and TEQs were shifted to larger particles with a decreasing altitude. Notably, PCDFs distributed extensively among aerosol size fractions based on their chlorination level during all sampling periods. Overall mass median diameter (MMDo) of total-PCDD/F-TEQs for fugitive areas in the TSU plant were higher than those from outside-plant emission sources.

Hygroscopic growth of tropospheric particle number size distributions over the North China Plain

The hygroscopic growth of atmospheric submicrometer particle size distributions (diameter Dp ranging from 22 to 900 nm) was studied at a rural/suburban site in the North China Plain within the framework of the international Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing‐2006) research project. The goal was to characterize the regional aerosol in the polluted northeastern plain in China. Size descriptive hygroscopic growth factors (DHGFs) were determined as a function of relative humidity (RH) by relating the particle number size distribution at a dry condition (&lt;30%) to those measured at higher RHs (RH = 56, 76, 85, and 91%) for the diameter range from 30 to 300 nm. In the size range of the accumulation mode (Dp &gt; 100 nm), the DHGF are substantially higher than in the Aitken particle mode (Dp &lt; 100 nm) as a result of different chemical composition. The size‐dependent behavior of the DHGF highlights the relevance of particulate sulfate production over the North China Plain, accomplished by secondary formation from the gas phase and, potentially, liquid phase processes in convective clouds. Furthermore, all results concerning the DHGF show a significant dependency on meteorological air masses. The hygroscopic growth of accumulation mode particles correlates significantly with the PM1‐mass fraction of sulfate ions determined by chemical analysis. Finally, this investigation provides a parameterization of the hygroscopic growth of 250‐nm particles, which might be useful when predicting visibility and radiative forcing and performing atmospheric aerosol model validations.

Particle size distributions in the Eastern Mediterranean troposphere

Abstract. Atmospheric particle size distributions were measured on Crete island, Greece in the Eastern Mediterranean during an intensive field campaign between 28 August and 20 October, 2005. Our instrumentation combined a differential mobility particle sizer (DMPS) and an aerodynamic particle sizer (APS) and measured number size distributions in the size range 0.018 μm–10 μm. Four time periods with distinct aerosol characteristics were discriminated, two corresponding to marine and polluted air masses, respectively. In marine air, the sub-μm size distributions showed two particle modes centered at 67 nm and 195 nm having total number concentrations between 900 and 2000 cm−3. In polluted air masses, the size distributions were mainly unimodal with a mode typically centered at 140 nm, with number concentrations varying between 1800 and 2900 cm−3. Super-μm particles showed number concentrations in the range from 0.01 to 2.5 cm−3 without any clear relation to air mass origin. A small number of short-lived particle nucleation events were recorded, where the calculated particle formation rates ranged between 1.1–1.7 cm−3 s−1. However, no particle nucleation and growth events comparable to those typical for the continental boundary layer were observed. Particles concentrations (Diameter &lt;50 nm) were low compared to continental boundary layer conditions with an average concentration of 300 cm−3. The production of sulfuric acid and its subsequently condensation on preexisting particles was examined with the use of a simplistic box model. These calculations suggested that the day-time evolution of the Aitken particle population was governed mainly by coagulation and that particle formation was absent during most days.

Comparison of Two Approaches to Modeling Atmospheric Aerosol Particle Size Distributions

This paper compares two approaches to modeling (smoothing) aerosol particle size distribution (particle counts for specified diameter intervals): i) the semiparametric approach based on a maximum likelihood fitting of lognormal (LN) mixtures at each time separately, followed by smoothing parameter tracks, ii) the nonparametric approach based on a kernel-like smoothing as an application of the gnostic theory of uncertain data. The specific advantages and disadvantages of both the semiparametric and nonparametric approaches are discussed and illustrated using real data containing a day-long time series of size spectra measurements.