Source Of Aerosol Particles Research Articles

Variability of air ion concentrations in urban Paris

Abstract. Air ion concentrations influence new particle formation and consequently the global aerosol as potential cloud condensation nuclei. We aimed to evaluate air ion concentrations and characteristics of new particle formation events (NPF) in the megacity of Paris, France, within the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric Pollution and climate effects, and Integrated tools for assessment and mitigation) project. We measured air ion number size distributions (0.8–42 nm) with an air ion spectrometer and fine particle number concentrations (> 6 nm) with a twin differential mobility particle sizer in an urban site of Paris between 26 June 2009 and 4 October 2010. Air ions were size classified as small (0.8–2 nm), intermediate (2–7 nm), and large (7–20 nm). The median concentrations of small and large ions were 670 and 680 cm−3, respectively, (sum of positive and negative polarities), whereas the median concentration of intermediate ions was only 20 cm−3, as these ions were mostly present during new particle formation bursts, i.e. when gas-to-particle conversion produced fresh aerosol particles from gas phase precursors. During peaks in traffic-related particle number, the concentrations of small and intermediate ions decreased, whereas the concentrations of large ions increased. Seasonal variations affected the ion population differently, with respect to their size and polarity. NPF was observed in 13 % of the days, being most frequent in spring and late summer (April, May, July, and August). The results also suggest that NPF was favoured on the weekends in comparison to workdays, likely due to the lower levels of condensation sinks in the mornings of weekends (CS weekdays 09:00: 18 × 10−3 s−1; CS weekend 09:00: 8 × 10−3 s−1). The median growth rates (GR) of ions during the NPF events varied between 3 and 7 nm h−1, increasing with the ion size and being higher on workdays than on weekends for intermediate and large ions. The median GR of small ions on the other hand were rather similar on workdays and weekends. In general, NPF bursts changed the diurnal cycle of particle number as well as intermediate and large ions by causing an extra peak between 09:00 and 14:00. On average, during the NPF bursts the concentrations of intermediate ions were 8.5–10 times higher than on NPF non-event days, depending on the polarity, and the concentrations of large ions and particles were 1.5–1.8 and 1.2 times higher, respectively. Because the median concentrations of intermediate ions were considerably higher on NPF event days in comparison to NPF non-event days, the results indicate that intermediate ion concentrations could be used as an indication for NPF in Paris. The results suggest that NPF was a source of ions and aerosol particles in Paris and therefore contributed to both air quality degradation and climatic effects, especially in the spring and summer.

Characteristics and sources of submicron aerosols above the urban canopy (260 m) in Beijing, China, during the 2014 APEC summit

Abstract. The megacity of Beijing has experienced frequent severe fine particle pollution during the last decade. Although the sources and formation mechanisms of aerosol particles have been extensively investigated on the basis of ground measurements, real-time characterization of aerosol particle composition and sources above the urban canopy in Beijing is rare. In this study, we conducted real-time measurements of non-refractory submicron aerosol (NR-PM1) composition at 260 m at the Beijing 325 m meteorological tower (BMT) from 10 October to 12 November 2014, by using an aerosol chemical speciation monitor (ACSM) along with synchronous measurements of size-resolved NR-PM1 composition near ground level using a high-resolution time-of-flight aerosol mass spectrometer (HR–ToF–AMS). The NR-PM1 composition above the urban canopy was dominated by organics (46 %), followed by nitrate (27 %) and sulfate (13 %). The high contribution of nitrate and high NO3− / SO42− mass ratios illustrates an important role of nitrate in particulate matter (PM) pollution during the study period. The organic aerosol (OA) was mainly composed of secondary OA (SOA), accounting for 61 % on an average. Different from that measured at the ground site, primary OA (POA) correlated moderately with SOA, likely suggesting a high contribution from regional transport above the urban canopy. The Asia–Pacific Economic Cooperation (APEC) summit with strict emission controls provides a unique opportunity to study the impacts of emission controls on aerosol chemistry. All aerosol species were shown to have significant decreases of 40–80 % during APEC from those measured before APEC, suggesting that emission controls over regional scales substantially reduced PM levels. However, the bulk aerosol composition was relatively similar before and during APEC as a result of synergetic controls of aerosol precursors. In addition to emission controls, the routine circulations of mountain–valley breezes were also found to play an important role in alleviating PM levels and achieving the "APEC blue" effect. The evolution of vertical differences between 260 m and the ground level was also investigated. Our results show complex vertical differences during the formation and evolution of severe haze episodes that are closely related to aerosol sources and boundary-layer dynamics.

The influence of marine microbial activities on aerosol production: A laboratory mesocosm study

AbstractThe oceans cover most of the Earth's surface, contain nearly half the total global primary biomass productivity, and are a major source of atmospheric aerosol particles. Here we experimentally investigate links between biological activity in seawater and sea spray aerosol (SSA) flux, a relationship of potential significance for organic aerosol loading and cloud formation over the oceans and thus for climate globally. Bubbles were generated in laboratory mesocosm experiments either by recirculating impinging water jets or glass frits. Experiments were conducted with Atlantic Ocean seawater collected off the eastern end of Long Island, NY, and with artificial seawater containing cultures of bacteria and phytoplankton Thalassiosira pseudonana, Emiliania huxleyi, and Nannochloris atomus. Changes in SSA size distributions occurred during all phases of bacterial and phytoplankton growth, as characterized by cell concentrations, dissolved organic carbon, total particulate carbon, and transparent exopolymer particles (gel‐forming polysaccharides representing a major component of biogenic exudate material). Over a 2 week growth period, SSA particle concentrations increased by a factor of less than 2 when only bacteria were present and by a factor of about 3 when bacteria and phytoplankton were present. Production of jet‐generated SSA particles of diameter less than 200 nm increased with time, while production of all particle diameters increased with time when frits were used. The implications of a marine biological activity dependent SSA flux are discussed.

Incorporation of new particle formation and early growth treatments into WRF/Chem: Model improvement, evaluation, and impacts of anthropogenic aerosols over East Asia

Abstract New particle formation (NPF) provides an important source of aerosol particles and cloud condensation nuclei, which may result in enhanced cloud droplet number concentration (CDNC) and cloud shortwave albedo. In this work, several nucleation parameterizations and one particle early growth parameterization are implemented into the online-coupled Weather Research and Forecasting model coupled with chemistry (WRF/Chem) to improve the model's capability in simulating NPF and early growth of ultrafine particles over East Asia. The default 8-bin over the size range of 39 nm–10 μm used in the Model for Simulating Aerosol Interactions and Chemistry aerosol module is expanded to the 12-bin over 1 nm–10 μm to explicitly track the formation and evolution of new particles. Although model biases remain in simulating H2SO4, condensation sink, growth rate, and formation rate, the evaluation of July 2008 simulation identifies a combination of three nucleation parameterizations (i.e., COMB) that can best represent the atmospheric nucleation processes in terms of both surface nucleation events and the resulting vertical distribution of ultrafine particle concentrations. COMB consists of a power law of Wang et al. (2011) based on activation theory for urban areas in planetary boundary layer (PBL), a power law of Boy et al. (2008) based on activation theory for non-urban areas in PBL, and the ion-mediated nucleation parameterization of YU10 for above PBL. The application and evaluation of the improved model with 12-bin and the COMB nucleation parameterization in East Asia during January, April, July, and October in 2001 show that the model has an overall reasonably good skill in reproducing most observed meteorological variables and surface and column chemical concentrations. Relatively large biases in simulated precipitation and wind speeds are due to inaccurate surface roughness and limitations in model treatments of cloud formation and aerosol-cloud-precipitation interactions. Large biases in the simulated surface concentrations of PM10, NOx, CO, SO2, and VOCs at some sites are due in part to possible underestimations of emissions and in part to inaccurate meteorological predictions. The simulations of 2001 show that anthropogenic aerosols can increase aerosol optical depth by 64.0–228.3%, CDNC by 40.2–76.4%, and cloud optical thickness by 14.3–25.3%; they can reduce surface net shortwave radiation by up to 42.5–52.8 W m−2, 2-m temperature by up to 0.34–0.83 °C, and PBL height by up to 76.8–125.9 m. Such effects are more significant than those previously reported for the U.S. and Europe.

Comparative analysis of chemical composition and sources of aerosol particles in urban Beijing during clear, hazy, and dusty days using single particle aerosol mass spectrometry

A single particle aerosol mass spectrometer (SPAMS) was employed to characterize the particles in urban Beijing in the spring of 2011. The whole sampling time was divided into clear, hazy, and dusty day periods. Based on SPAMS results, the chemical composition of size-resolved particles in five major classes, including K-rich, carbonaceous, industry metal, dust, and Na-rich particles, and their corresponding sources were compared during clear, hazy, and dusty days. Air mass back trajectories are used to identify likely source regions for each period. Under stagnant meteorological conditions, local and regional emissions are a key factor in haze formation. K-rich and carbonaceous particles dominated under all conditions (25–54%), with higher contributions (23% and 29%) from industrial metal particles during hazy days, which could be attributed to the emission of biomass burning, coal combustion, and vehicle exhaust during all periods, whereas industrial metal processes are also a likely source for K-rich particles during hazy days. The aging of particles was observed over the whole sampling period, as evidenced by the presence of secondary species in all particle classes. Industrial metal particles possibly originate from industrial metal processes, vehicle exhaust, and coal combustion etc, while road and soil dust is also a possible source during dusty days. Dust particles increased greatly (17%) in a dust storm event with a coarse mode distribution, which are mainly associated with the mineral dust from deserted regions, whereas they could originate from local dust and coal combustion during non-dusty days. Last, Na-rich particles are mainly associated with industrial metal particles, coal, and fuel combustion during hazy days, and mineral dust during dusty days, respectively. Sea salt is a possible source of Na-rich particles under all conditions. Our analysis could shed a light on the understanding of the different source apportionment of aerosol particles under different meteorology/pollution conditions.

Nocturnal aerosol particle formation in the North China Plain

New particle formation is one of the major sources of atmospheric aerosol particles. Beside daytime nucleation, nocturnal new particle formation was also found in different regions around the world. Compared with daytime nucleation events, the understanding of nocturnal ones is still sparse. The variety of aerosol particle physico-chemical properties, including particle number size distribution, volatility and hygroscopicity were measured in the North China Plain during July–August 2013. During the observation period, rapid increase in ultrafine particle number concentration was attributed to new particle formation. The nocturnal new particle formation rate was 45 cm–3s–1, which is 1.25 times higher than an observed daytime value. Condensation sink was found to be 0.055 s–1.

Individual particle analysis of aerosols collected at Lhasa City in the Tibetan Plateau

To understand the composition and major sources of aerosol particles in Lhasa City on the Tibetan Plateau (TP), individual particles were collected from 2 February to 8 March, 2013 in Tibet University. The mean concentrations of both PM2.5 and PM10 during the sampling were 25.7±21.7 and 57.2±46.7μg/m3, respectively, much lower than those of other cities in East and South Asia, but higher than those in the remote region in TP like Nam Co, indicating minor urban pollution. Combining the observations with the meteorological parameters and back trajectory analysis, it was concluded that local sources controlled the pollution during the sampling. Transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectra (EDS) was used to study 408 particles sampled on four days. Based on the EDS analysis, a total of 8 different particle categories were classified for all 408 particles, including Si-rich, Ca-rich, soot, K-rich, Fe-rich, Pb-rich, Al-rich and other particles. The dominant elements were Si, Al and Ca, which were mainly attributed to mineral dust in the earth's crust such as feldspar and clay. Fe-, Pb-, K-, Al-rich particles and soot mainly originated from anthropogenic sources like firework combustion and biomass burning during the sampling. During the sampling, the pollution mainly came from mineral dust, while the celebration ceremony and religious ritual produced a large quantity of anthropogenic metal-bearing particles on 9 and 25 February 2013. Cement particles also had a minor influence. The data obtained in this study can be useful for developing pollution control strategies.

Elucidating carbonaceous aerosol sources by the stable carbon δ13CTC ratio in size-segregated particles

Carbonaceous aerosol sources were investigated by measuring the stable carbon isotope ratio (δ13CTC) in size-segregated aerosol particles. The samples were collected with a micro-orifice uniform deposit impactor (MOUDI) in 11 size intervals ranging from 0.056μm to 18μm. The aerosol particle size distribution obtained from combined measurements with a scanning mobility particle sizer (SMPS; TSI 3936) and an aerosol particle sizer (APS; TSI 3321) is presented for comparison with MOUDI data. The analysis of δ13CTC values revealed that the total carbonaceous matter in size-segregated aerosol particles significantly varied from −23.4±0.1‰ in a coarse mode to −30.1±0.5‰ in a fine mode. A wide range of the δ13CTC values of size-segregated aerosol particles suggested various sources of aerosol particles contributing to carbonaceous particulate matter. Therefore, the source mixing equation was applied to verify the idea of mixing of two sources: continental non-fossil and fossil fuel combustion. The obtained δ13CTC value of aerosol particles originating from fossil fuel combustion was −28.0 to −28.1‰, while the non-fossil source δ13CTC value was in the range of −25.0 to −25.5‰. The two source mixing model applied to the size-segregated samples revealed that the fossil fuel combustion source contributed from 100% to 60% to the carbonaceous particulate matter in the fine mode range (Dp < 1μm). Meanwhile, the second source, continental non-fossil, was the main contributor in the coarse fraction (Dp>2μm). The particle range from 0.5 to 2.0μm was identified as a transition region where two sources almost equally contributed to carbonaceous particulate matter. The proposed mixing model offers an alternative method for determining major carbonaceous matter sources where radiocarbon analysis may lack the sensitivity (as in size-segregated samples).

Spatio-Temporal Distribution of Aerosol and Cloud Properties over Sindh Using MODIS Satellite Data and a HYSPLIT Model

In this study, aerosols spatial, seasonal and temporal variations over Sindh, Pakistan were analyzed which can lead to variations in the microphysics of clouds as well. All cloud optical properties were analyzed using Moderate Resolution Imaging Spectroradiometer (MODIS) data for 12 years from 2001 to 2013. We also monitored origin and movements of air masses that bring aerosol particles and may be considered as the natural source of aerosol particles in the region. For this purpose, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to make trajectories of these air masses from their sources. Aerosol optical depth (AOD) high values were observed in summer during the monsoon period (June–August). The highest AOD values in July were recorded ranges from 0.41 to 1.46. In addition, low AOD values were found in winter season (December–February) particularly in December, ranges from 0.16 to 0.69. We then analyzed the relationship between AOD and Ångström exponent that is a good indicator of the size of an aerosol particle. We further described the relationships of AOD and four cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP) by producing regional correlation maps of their data values. The analyses showed negative correlation between AOD and Ångström exponent especially in central and western Sindh. The correlation between AOD and WV was throughout positive with high correlation values > 0.74 in whole Sindh except eastern most arid strip of the Thar Desert in the region. The correlation between AOD and CF was positive in southern Sindh and goes to negative in northern Sindh. AOD showed a positive correlation with CTP and CTT in northern Sindh and a negative correlation in southern Sindh. All these correlations were observed to be dependent on the meteorological conditions for all of the ten sites investigated.

Chemical composition and sources of coastal marine aerosol particles during the 2008 VOCALS-REx campaign

Abstract. The chemical composition of aerosol particles (Dp ≤ 1.5 μm) was measured over the southeast Pacific Ocean during the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-Rex) between 16 October and 15 November 2008 using the US Department of Energy (DOE) G-1 aircraft. The objective of these flights was to gain an understanding of the sources and evolution of these aerosols, and of how they interact with the marine stratus cloud layer that prevails in this region of the globe. Our measurements showed that the marine boundary layer (MBL) aerosol mass was dominated by non-sea-salt SO42−, followed by Na+, Cl−, Org (total organics), NH4+, and NO3−, in decreasing order of importance; CH3SO3− (MSA), Ca2+, and K+ rarely exceeded their limits of detection. Aerosols were strongly acidic with a NH4+ to SO42− equivalents ratio typically &lt; 0.3. Sea-salt aerosol (SSA) particles, represented by NaCl, exhibited Cl− deficits caused by both HNO3 and H2SO4, but for the most part were externally mixed with particles, mainly SO42−. SSA contributed only a small fraction of the total accumulation mode particle number concentration. It was inferred that all aerosol species (except SSA) were of predominantly continental origin because of their strong land-to-sea concentration gradient. Comparison of relative changes in median values suggests that (1) an oceanic source of NH3 is present between 72° W and 76° W, (2) additional organic aerosols from biomass burns or biogenic precursors were emitted from coastal regions south of 31° S, with possible cloud processing, and (3) free tropospheric (FT) contributions to MBL gas and aerosol concentrations were negligible. The very low levels of CH3SO3− observed as well as the correlation between SO42− and NO3− (which is thought primarily anthropogenic) suggest a limited contribution of DMS to SO42− aerosol production during VOCALS.

Ambient particle characterization by single particle aerosol mass spectrometry in an urban area of Beijing

To investigate the composition and possible sources of aerosol particles in Beijing urban area, a single particle aerosol mass spectrometer (SPAMS) was deployed from April 22 to May 4, 2011. 510,341 particles out of 2,953,200 sized particles were characterized by SPAMS in combination with the ART-2a neural network algorithm. The particles were classified as rich-K (39.79%), carbonaceous species (32.7%), industry metal (19.2%), dust (5.7%), and rich-Na (1.76%). Industrial emissions related particles, rich-Fe, rich-Pb, and K-nitrate, were the major components of aerosol particles during haze periods, which were mainly from the steel plants and metal smelting processes around Beijing. Under stagnant meterological conditions, these regional emissions have a vital effect on haze formation. Organic carbon (OC) particles were attributed to biomass burning. NaK-EC was likely to come from local traffic emissions. Internally mixed organic and elemental carbon (OCEC) was found to be from possible sources of local traffic emission and biomass burning. It was found that coarse dust particles were mainly composed of four different types of dust particles, dust-Si, dust-Ca, dust-Al, and dust-Ti. It is the first time that SPAMS was used to study a dust storm in Beijing. Our results showed that SPAMS could be a powerful tool in the identification and apportionment of aerosol sources in Beijing, providing useful reference information for environmental control and management.

Urban background levels of particle number concentration and sources in Vilnius, Lithuania

This study presents results of research on urban aerosol particles with a focus on the aerosol particle number concentration (PNC) and the particle size distribution. The real time measurements of aerosol PNC (>4.5nm) and number size distributions (9–840nm) were performed. The seasonal variations essentially comprised the minimum monthly mean in October 2010 (3400±3000cm−3) and the maximum in April 2011 (19,000±15,000cm−3). The mean annual PNC was 10,000±8000cm−3 with an average mode size of 30–50nm. The presence of strong diurnal patterns in aerosol PNC was evident as a direct effect of three sources of aerosol particles (nucleation, traffic, and residential heating). Hybrid receptor modeling potential source contribution function (PSCF) and concentration weighted trajectory (CWT) were used by incorporating 72-h backward trajectories and measurements of PNC in Vilnius. The results of trajectory clustering and the PSCF method demonstrated that possible additional source areas contributing to the elevated particle number concentration in Vilnius could be industrial areas in central Europe. Principal component analysis (PCA) revealed highest loadings for PNC, PM10, NOx, NO, NO2 and SO2 concentrations, indicating combustion processes occurring in vehicle engines and use of sulfur-containing fossil fuels for residential heating.

Anthropogenic sources of aerosol particles in a football stadium: Real-time characterization of emissions from cigarette smoking, cooking, hand flares, and color smoke bombs by high-resolution aerosol mass spectrometry

Aerosol particles from several anthropogenic sources associated with football stadia including cooking, cigarette smoking, burning of color smoke bombs and hand flares were analyzed by high-resolution aerosol mass spectrometry. The physical and chemical characteristics of these different aerosols, in particular the organic fraction, were explored in laboratory studies to obtain robust references. These data were compared with field campaign results from a Bundesliga (German football league) match in the Coface Arena (Mainz, Germany) on 20th April 2012. The field measurement revealed a strongly elevated mass concentration of organic aerosols (OA) compared to background levels showing a temporal structure clearly related to the match. PMF analysis established that during the football match event cigarette smoke was the predominant component of submicron organic aerosol (67% of total OA). Cooking emissions from food outlets within the stadium correlated well with the sales figures of the catering stations and were also found to be of relevance (24% of total OA) especially in the period before kickoff. Pyrotechnics were not observed during this football match and no signatures of these sources were found in the mass spectra from the stadium measurements. All species that were elevated during the football match returned to their initial background levels within one hour after the match had finished. This demonstrates a good ventilation capacity of the open-topped Coface Arena.

Modeling regional deposited dose of submicron aerosol particles

We developed a simple model to calculate the regional deposited dose of submicron aerosol particles in the respiratory system. This model incorporates measured outdoor and modeled indoor particle number size distributions, detailed activity patterns of three age groups (teens, adults, and the elderly), semi-empirical estimation of the regional deposition fraction, hygroscopic properties of urban aerosols, and reported breathing minute volumes. We calculated the total and regional deposited dose based on three concentration metrics: particle number (PN), mass (PM), and surface area (PSA). The 24-h total deposited dose of fine particles in adult males was around 40μg (57×109particles, 8×102mm2) and 41μg (40×109particles, 8×102mm2) on workdays and weekends, respectively. The total and regional 24-h deposited dose based on any of the metrics was at most 1.5 times higher in males than in females. The deposited dose values in the other age groups were slightly different than in adults. Regardless of the particle size fraction or the deposited dose metric, the pulmonary/alveolar region received the largest fraction of the deposited dose. These values represent the lowest estimate of the deposited dose and they are expected to be higher in real-life conditions after considering indoor sources of aerosol particles and spatial variability of outdoor aerosols. This model can be extended to youngsters (<12years old) after gaining accurate information about the deposition fraction inside their respiratory system and their breathing pattern. This investigation is foreseen to bridge the gap between exposure and response in epidemiological studies.

我国雾-霾成因及其治理的思考

We assess the relationship among haze-fog, aerosol and meteorological conditions, and analyze the chemical compositions and sources of aerosol particles, as well make some suggestions for aerosol control strategy. Present-day haze and fog in China are both dependent on atmospheric aerosol loading and weather conditions. The secondary aerosol formation and changes, which dominate the total aerosol mass and are highly influenced by meteorological conditions, characterized the regional haze feature in East China. In the Huabei Plain, which suffers from intense haze and fog, secondary organic aerosols are found to have similar role like sulphate, contributing to aerosol mass during both new particle formation and aging stages. The organic aerosol mix with inorganic ones to form hygroscopic particles earlier at ～70% relative humidity (RH), but which have a small hygroscopic growth factor. The hygroscopic aerosol particles would also make the PM2.5 mass monitoring at China exhibiting unrealistic high concentration under high RH stage. About 70% of these particles are internally mixed with two or three different aerosol components. Most mineral particles are covered with visible coatings, including fly ash, soot and metal particles, leading to have more secondary aerosol formed on their surface. This complicates haze formation in China. Under high aerosol particle concentrations, greater numbers of cloud droplets with relative small-size are observed in low clouds relative to high clouds; and the associated aerosol impact on cloud microphysical processe is different in less polluted areas. At low supersaturation most of hygroscopic particles larger than 150 nm form cloud condensation nuclei (CCN), and the impact of aerosol chemical composition on CCN activation is significant. There is a high aerosol concentration in China relative to other areas in the world, except for urban South Asia. These particles form under complex conditions and interact with clouds, resulting that present-day haze and fog in China both are not natural phenomenon. Haze and fog reduces surface radiation, making the atmosphere more stable, resulting in continuous coagulation, condensation, accumulation of aerosol, and more CCN activation, leading to serious and maintained haze-fog events. The heavy and persistent haze-fog between 6 and 16 January 2013 in East China was caused by both high aerosol loading and singular static weather conditions. We need to have adequate scientific judgment on the complexity and expectation of aerosol emission reduction in China. The government needs to make informed decisions and implement laws to maintain the health of its people, but this is not easy when we strive for economic growth. There is no easy solution to control aerosol sources, but the government should spare no effort to cut aerosol and their precursors gas emission. Regional pollution control is also very critical; a strong policy and protocol needs to be enforced by the central government to drive provincial leaders to make the necessary changes to ensure better air quality and quality of life for the population.

Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean

Abstract. The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics, including their significance, from eight flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number that influence droplet concentration. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were smaller in regions of enhanced particles near shore. However, physically thinner clouds, and not just higher droplet number concentrations from pollution, both contributed to the smaller droplets. Satellite measurements were used to show that cloud albedo was highest 500–1000 km offshore, and actually slightly lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

Long-term observations of aerosol size distributions in semi-clean and polluted savannah in South Africa

Abstract. This study presents a total of four years of sub-micron aerosol particle size distribution measurements in the southern African savannah, an environment with few previous observations covering a full seasonal cycle and the size range below 100 nm. During the first 19 months, July 2006–January 2008, the measurements were carried out at Botsalano, a semi-clean location, whereas during the latter part, February 2008–May 2010, the measurements were carried out at Marikana (approximately 150 km east of Botsalano), which is a more polluted location with both pyrometallurgical industries and informal settlements nearby. The median total concentration of aerosol particles was more than four times as high at Marikana than at Botsalano. In the size ranges of 12–840 nm, 50–840 nm and 100–840 nm the median concentrations were 1856, 1278 and 698 particles cm−3 at Botsalano and 7805, 3843 and 1634 particles cm−3 at Marikana, respectively. The diurnal variation of the size distribution for Botsalano arose as a result of frequent regional new particle formation. However, for Marikana the diurnal variation was dominated by the morning and evening household burning in the informal settlements, although regional new particle formation was even more frequent than at Botsalano. The effect of the industrial emissions was not discernible in the size distribution at Marikana although it was clear in the sulphur dioxide diurnal pattern, indicating the emissions to be mostly gaseous. Seasonal variation was strongest in the concentration of particles larger than 100 nm, which was clearly elevated at both locations during the dry season from May to September. In the absence of wet removal during the dry season, the concentration of particles larger than 100 nm had a correlation above 0.7 with CO for both locations, which implies incomplete burning to be an important source of aerosol particles during the dry season. However, the sources of burning differ: at Botsalano the rise in concentration originates from regional wild fires, while at Marikana domestic heating in the informal settlements is the main source. Air mass history analysis for Botsalano identified four regional scale source areas in southern Africa and enabled the differentiation between fresh and aged rural background aerosol originating from the clean sector, i.e., western sector with very few large anthropogenic sources. Comparison to size distributions published for other comparable environments in Northern Hemisphere shows southern African savannah to have a unique combination of sources and meteorological parameters. The observed strong link between combustion and seasonal variation is comparable only to the Amazon basin; however, the lack of long-term observations in the Amazonas does not allow a quantitative comparison. All the data presented in the figures, as well as the time series of monthly mean and median size distributions are included in numeric form as a Supplement to provide a reference point for the aerosol modelling community.

산업단지내 미세먼지 및 토양입자의 개별입자 분석

Aerosol characterization study for individual particle in Busan metropolitan industrial complex was carried out from December 2010 to August 2011. SEM(scanning electron microscope)-EDX(energy dispersive x-ray) analysis was used for the analysis of 600 single particles during the sampling periods to identify non-metallic aerosol particle sources. Average <TEX>$PM_{10}$</TEX> concentration was 65.5 <TEX>${\mu}g/m^3$</TEX> in summer, 104.1 <TEX>${\mu}g/m^3$</TEX> in winter during the sample periods. And Average <TEX>$PM_{2.5}$</TEX> concentration was 24.5 <TEX>${\mu}g/m^3$</TEX> in summer, 64.5 <TEX>${\mu}g/m^3$</TEX> in winter individually. Particle density, enrichment factor, correlation analysis, principle component analysis were performed based on chemical composition data. Particle density distribution was measured to 2~4 <TEX>$g/cm^3$</TEX>, and the density of <TEX>$PM_{2.5}$</TEX> was measured above 3 <TEX>$g/cm^3$</TEX>. In general, the elements Si, Ca, Fe and Al concentrations were higher in all samples of individual particles. The non-ferrous elements Zn, Br, Pb, Cu concentrations were higher in summer than in winter. The concentrations were not changed with the seasons because of non-ferrous industry emission pattern.

Source categories and contribution of biomass smoke to organic aerosol over the southeastern Tibetan Plateau

An intensive measurement campaign was conducted at a mountain and suburban site at the edge of the southeastern Tibetan Plateau during spring. Concentrations of PM2.5, carbonaceous species (OC and EC) and anhydrosugars (levoglucosan, mannosan and galactosan) as well as their ratios were utilized to identify possible biomass burning categories and contributions of biomass burning smoke to ambient aerosols. The average concentrations of levoglucosan and mannosan were 193.8 and 12.4 ng m−3, respectively at the mountain site, and 713 and 61.5 ng m−3 respectively at the suburban site. According to characteristic levoglucosan/mannosan (Lev/Man) and mannosan/galactosan (Man/Gal) ratios, we identified for the first time that mixed smoke particles (18.5, 72.3 and 9.1% for crop residues, softwood and hard wood respectively) derived from the study region and Southeast Asia contributed to the aerosol burden in the southeastern Tibetan Plateau. The biomass smoke contributions to organic carbon and organic matter were estimated to be 28.4% and 18.9–25.7% respectively at the mountain site and 38.3% and 33.5–45.4% respectively at the suburban site. The large contribution estimates indicate that biomass burning was an important anthropogenic/natural source of aerosol particles which impact regional atmospheric chemistry and climate in the southeastern Tibetan Plateau.

Size resolved measurements of springtime aerosol particles over the northern South China Sea

Large sources of aerosol particles and their precursors are ubiquitous in East Asia. Such sources are known to impact the South China Sea (henceforth SCS), a sometimes heavily polluted region that has been suggested as particularly vulnerable to climate change. To help elucidate springtime aerosol transport into the SCS, an intensive study was performed on the remote Dongsha (aka Pratas) Islands Atoll in spring 2010. As part of this deployment, a Davis Rotating-drum Uniform size-cut Monitor (DRUM) cascade impactor was deployed to collect size-resolved aerosol samples at the surface that were analyzed by X-ray fluorescence for concentrations of selected elements. HYSPLIT backtrajectories indicated that the transport of aerosol observed at the surface at Dongsha was occurring primarily from regions generally to the north and east. This observation was consistent with the apparent persistence of pollution and dust aerosol, along with sea salt, in the ground-based dataset. In contrast to the sea-level observations, modeled aerosol transport suggested that the westerly flow aloft (∼700 hPa) transported smoke-laden air toward the site from regions from the south and west. Measured aerosol optical depth at the site was highest during time periods of modeled heavy smoke loadings aloft. These periods did not coincide with elevated aerosol concentrations at the surface, although the model suggested sporadic mixing of this free-tropospheric aerosol to the surface over the SCS. A biomass burning signature was not clearly identified in the surface aerosol composition data, consistent with this aerosol type remaining primarily aloft and not mixing strongly to the surface during the study. Significant vertical wind shear in the region also supports the idea that different source regions lead to varying aerosol impacts in different vertical layers, and suggests the potential for considerable vertical inhomogeneity in the SCS aerosol environment.