Aerosol Air Pollution Research Articles

On the additional risk for human health in the use of sandblasting of building walls.

In 2021, concentrations of heavy metals (Ba, Cr, Fe, Mn, Pb, Ru, Sr, Zn, Zr) and radiocesium (137Cs) were measured in 13 locations in Vilnius in surface samples of walls and facades of buildings built of yellow bricks in order to evaluate possible aerosol air pollution due to sandblasting. The activity concentrations of 137Cs appeared there as a result of global fallout and precipitation of the products of the accident at the Chernobyl Nuclear Power Plant, and the concentration of Pb, as a component of road transport emissions. Other trace elements turned out to be impurities in the material of yellow bricks. In spring 2018, sandblasting of the walls of the building adjacent to the school led to the long-term significant aerosol contamination of school premises (up to 660µg/m3). Due to sandblasting, the surface of the school sport yard was covered with a thin layer of scraped particles, which were transported by gusts of wind into the school premises. Sandblasting of walls and facades can also be a source of aerosols with 137Cs activity concentrations reaching ~ 40Bq/kg and Pb - up to 98ppm. Estimates show that along with 137Cs, the formation of aerosols with activity concentrations of 239, 240Pu reaching 1.6Bq/kg is possible. Isotopes of 239, 240Pu are analogues of calcium and, when ingested, are deposited in the bones. The ingress of radioactive aerosols into the respiratory tract, especially of children of primary school age, creates additional risks of malignant diseases.

ВЛИЯНИЕ СИЛЬНОГО АЭРОЗОЛЬНОГО ЗАГРЯЗНЕНИЯ ВОЗДУХА НА ЭВОЛЮЦИЮ КОНВЕКТИВНЫХ ОБЛАКОВ ВО ВРЕМЯ ГРОЗЫ В КИТАЕ ПО РЕЗУЛЬТАТАМ ТРЕХМЕРНОГО ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Numerical simulation of evolution of a convective cloud and precipitation during a thunderstorm event that took place on August 11, 2017 in Beijing (China) against a background of high aerosol air pollution was performed using a numerical nonstationary three-dimensional model. Different microphysical parameters of drops and ice particles which depend on aerosol pollution of the atmosphere, were varied: an autoconversion threshold for cloud droplets and raindrops and parameters of raindrop and hailstone size distribution. It was found for this case that liquid drops do not play a significant role in the convective cloud evolution. The effect of aerosol pollution both on the raindrop size spectrum and on the transition of cloud droplets to raindrops does not influence significantly dynamic, microphysical and electrical properties of the cloud. At the same time, the change in the ice particle spectrum towards the size decrease that happens under the influence of increased aerosol pollution, has a significant impact on the evolution of the cloud and precipitation. The amount of precipitation decreases both within the cloud and on the underlying surface. However, the lightning activity of the cloud changes little

Effects of High Aerosol Air Pollution on the Evolution of Convective Clouds during a Thunderstorm in China According to Three-dimensional Numerical Simulations

Effects of High Aerosol Air Pollution on the Evolution of Convective Clouds during a Thunderstorm in China According to Three-dimensional Numerical Simulations

Аномальное аэрозольное загрязнение воздуха в Москве вблизи локального антропогенного источника в июле 2021 года

The paper analyzes the composition of surface aerosol close to the local intense anthropogenic source of pollution associated with the active phase of demolition of multistorey buildings in the center of Moscow. An abnormal increase in the daytime PM10 aerosol particle concentration to 5 MPC for daily values and to 14 MPC for maximum single values was reinforced by unfavorable meteorological conditions in the middle of July 2021. Preliminary estimation of the power of the dust aerosol source and its effect on the aerosol air pollution in nearby areas of the city is performed. The extreme and background values of the aerosol mass concentration, its elemental composition and particle size distribution during this period are determined. It is necessary to take into account such point pollutant sources in estimating and forecasting environmental conditions in a densely populated city. Keywords: surface aerosol, local anthropogenic source, Moscow, aerosol mass concentration, elemental composition, meteorological conditions

Аномальное аэрозольное загрязнение воздуха в Москве вблизи локального антропогенного источника в июле 2021 года

The paper analyzes the composition of surface aerosol close to the local intense anthropogenic source of pollution associated with the active phase of demolition of multistorey buildings in the center of Moscow. An abnormal increase in the daytime PM10 aerosol particle concentration to 5 MPC for daily values and to 14 MPC for maximum single values was reinforced by unfavorable meteorological conditions in the middle of July 2021. Preliminary estimation of the power of the dust aerosol source and its effect on the aerosol air pollution in nearby areas of the city is performed. The extreme and background values of the aerosol mass concentration, its elemental composition and particle size distribution during this period are determined. It is necessary to take into account such point pollutant sources in estimating and forecasting environmental conditions in a densely populated city. Keywords: surface aerosol, local anthropogenic source, Moscow, aerosol mass concentration, elemental composition, meteorological conditions

Dispersion and modeling discussion of aerosol air pollution caused during mining and processing of open-cast mines

Given the importance of mining as a source of Total Suspended Particles (TSP) and fine Particulate Matters (PM10), it is important to develop appropriate methods for estimating emissions for use in modeling forecasts and to be aware of regulatory decisions. Development of site-specific emission estimation and also dispersion radius in copper mines would be a practical guide for environmental regulatory bodies in developing countries with incomplete local data. To address these needs, this research is presented, at an open-cast copper mine in mountainous area, using both one-year measurement observational and AERMOD emission modeling software based on documented Environment Protection Agency emission factors. Results demonstrate TSP dispersion predictions were in better agreement with the measured concentrations than those for PM10. This research finds that PM10 and TSP concentration are lowest in autumn and winter, respectively, while both have the highest concentration in summer. The maximum observed concentration of both pollutants is about 300 μg/m3 which is beyond the standard level. The study further shows that generally, concentration of TSP is three times of PM10. The dispersion radius of aerosols was 14 km with wide dispersion for TSP compared with PM10; so, could potentially pose serious environmental and health threats to the surrounding environment and community. The TSP and PM10 emission are about 3.242 and 0.969 kg per any ton of copper produced. This research was applied to a mountainous copper mine in NW Iran, one of the biggest surface mines all across the world (~ 300Mt/y).

Classification and source analysis of low-altitude aerosols in Beijing using fluorescence–Mie polarization lidar

The types of aerosols are essential for estimating radiative forcing effects, improving the lidar retrieval algorithms, and identifying aerosol sources. However, it is difficult to categorize the aerosols with similar optical properties based on lidar techniques. In this study, an approach was proposed to distinguish desert dust (DD), mineral dust (MD), air pollution aerosols (APA), and their mixtures (DD&MD, DD&APA, MD&APA, DD&MD&APA). We established the fluorescence–Mie​ polarization lidar (FMPL) system to categorize three types of main aerosols using the customized fluorescence-to-Mie ratio (FMR) and volume depolarization ratio (VDR) in the experiments from September 2017 to December 2018. Then, the mixture of the aerosols was classified by combining backward trajectory analysis. The feasibility of this method was verified through five typical cases in the paper, and it is proved that the method could be employed to study air pollution issues based on FMPL, which could provide references for the meteorological investigation.

Development of a laser complex for ecological monitoring of the atmosphere of urban and industrial areas

The object of research is methods of remote ecological monitoring of the surface layer of the atmosphere within residential areas and industrial zones of big cities. For the remote determination of the quantitative characteristics of gas and aerosol air pollution with high accuracy and spatial resolution, a mobile laser complex has been proposed. Determination of the composition and concentration of gas pollutants is carried out using two methods – the differential absorption method and the spontaneous Raman scattering (SRS) method. The differential absorption method is used to detect low concentrations of polluting gases along a stationary sounding path. The spontaneous Raman scattering method is used for remote detection of harmful gaseous substances at their concentrations exceeding the maximum permissible standards. SRS method used in the developed gas aerosol lidar allows one to obtain three-dimensional distributions of the concentrations of the gases being determined with a resolution of the order of one meter. This makes it possible to quickly and accurately identify environmentally hazardous sources of air pollution and reasonably apply penalties to violators of environmental standards. Remote analysis of the aerosol composition of the surface layer of the atmosphere is carried out using lidar holography methods, which were developed in the laboratory of radio and optical holography of V.N. Karazin Kharkiv National University (Ukraine). The difference in reflection from liquid and solid aerosol particles makes it possible to form polarization holograms and consider them separately for liquid and solid aerosols. Quantitative analysis of the composition and concentration of particles observed from their holographic images is characterized by a high level of sensitivity, since, unlike other known methods, it does not require a priori assumptions about the qualitative composition of the determined aerosol. Thus, due to the use of various physical principles of the interaction of laser radiation with gaseous and aerosol components of the air, the developed laser complex for environmental monitoring of the atmosphere is an effective means of monitoring the state of the air in the conditions of modern megacities.

Assessment of natural and anthropogenic aerosol air pollution in the Middle East using MERRA-2, CAMS data assimilation products, and high-resolution WRF-Chem model simulations

Abstract. Modern-Era Retrospective analysis for Research and Applications v.2 (MERRA-2), Copernicus Atmosphere Monitoring Service Operational Analysis (CAMS-OA), and a high-resolution regional Weather Research and Forecasting model coupled with chemistry (WRF-Chem) were used to evaluate natural and anthropogenic particulate matter (PM) air pollution in the Middle East (ME) during 2015–2016. Two Moderate Resolution Imaging Spectrometer (MODIS) retrievals – combined product Deep Blue and Deep Target (MODIS-DB&DT) and Multi-Angle Implementation of Atmospheric Correction (MAIAC) – and Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) observations as well as in situ PM measurements for 2016 were used for validation of the WRF-Chem output and both assimilation products. MERRA-2 and CAMS-OA assimilate AOD observations. WRF-Chem is a free-running model, but dust emission in WRF-Chem is tuned to fit AOD and aerosol volume size distributions obtained from AERONET. MERRA-2 was used to construct WRF-Chem initial and boundary conditions both for meteorology and chemical and aerosol species. SO2 emissions in WRF-Chem are based on the novel OMI-HTAP SO2 emission dataset. The correlation with the AERONET AOD is highest for MERRA-2 (0.72–0.91), MAIAC (0.63–0.96), and CAMS-OA (0.65–0.87), followed by MODIS-DB&DT (0.56–0.84) and WRF-Chem (0.43–0.85). However, CAMS-OA has a relatively high positive mean bias with respect to AERONET AOD. The spatial distributions of seasonally averaged AODs from WRF-Chem, assimilation products, and MAIAC are well correlated with MODIS-DB&DT AOD product. MAIAC has the highest correlation (R=0.8), followed by MERRA-2 (R=0.66), CAMS-OA (R=0.65), and WRF-Chem (R=0.61). WRF-Chem, MERRA-2, and MAIAC underestimate and CAMS-OA overestimates MODIS-DB&DT AOD. The simulated and observed PM concentrations might differ by a factor of 2 because it is more challenging for the model and the assimilation products to reproduce PM concentration measured within the city. Although aerosol fields in WRF-Chem and assimilation products are entirely consistent, WRF-Chem is preferable for analysis of regional air quality over the ME due to its higher spatial resolution and better SO2 emissions. The WRF-Chem’s PM background concentrations exceed the World Health Organization (WHO) guidelines over the entire ME. Mineral dust is the major contributor to PM (≈75 %–95 %) compared to other aerosol types. Near and downwind from the SO2 emission sources, nondust aerosols (primarily sulfate) contribute up to 30 % to PM2.5. The contribution of sea salt to PM in coastal regions can reach 5 %. The contributions of organic matter, black carbon and organic carbon to PM over the Middle East are insignificant. In the major cities over the Arabian Peninsula, the 90th percentile of PM10 and PM2.5 (particles with diameters less than 10 and 2.5 µm, respectively) daily mean surface concentrations exceed the corresponding Kingdom of Saudi Arabia air quality limits. The contribution of the nondust component to PM2.5 is <25 %, which limits the emission control effect on air quality. The mitigation of the dust effect on air quality requires the development of environment-based approaches like growing tree belts around the cities and enhancing in-city vegetation cover. The WRF-Chem configuration presented in this study could be a prototype of a future air quality forecast system that warns the population against air pollution hazards.

Simulating effects of aerosols on rainfall in southern Africa

Climate-aerosol model ECHAM5-HAM is employed to study effects of aerosol air pollution on rainfall in southern Africa. Aerosols effect the climate through light scattering and absorption, modification of cloud properties, and other indirect effects. The simulation model simulates the global climate on a grid and aerosol emissions from all major economic sectors as provided by the GAINS emission model. Using different model setups, we can separate the effect of aerosol light absorption due to black carbon and other aerosols, that of aerosols interacting with clouds through acting as cloud condensation nuclei and that through the ocean response. This is the first study of its kind to employ aerosol station measurements for model validation. Comparisons are done with previous plentiful studies for south Asia with many similarities in aerosol and rainfall climatology. We conclude that aerosols likely have a weak, negative effect on rainfall with internal variability dominating the simulation results, consistently with observed historical records. Aerosol light absorption does not seem to have a strong impact on rainfall. Meanwhile, the complexity of the problem also leaves uncertainty to the results. Regionally, the results show an opposite pattern of greenhouse gas projections that suggest a wet-get-wetter and dry-get-drier development due to global warming.

An aerosol air pollution episode affected by binary typhoons in east and central China

Previous studies have suggested that pollutant concentrations have the characteristics of initially rising and later falling in the main impact area of a typhoon. Whether this occurs in the typhoon's periphery or in zones even further away is still unknown. Based on ground observations of pollutant concentrations, meteorological parameters, aerosol optical depth, and WRF-Chem simulation, an aerosol air pollution episode affected by binary typhoons were analyzed over different regions in inland China. Before the typhoons made landfall, the weak surface winds and downdrafts were the crucial factors triggering the severe aerosol air pollution in east and central China. After landing, in the main impact area, aerosols were effectively removed due to precipitation scavenging and strong winds. However, beyond that area, the impact of the typhoons on pollution weakened with the increasing distance. Wuhan was at the edge of the typhoon impact zone, the changes of pollutant concentrations were similar to the main impact area, but the pollutants dispersed only due to the gales. Weinan site was farthest away from the typhoons, typhoons hardly affected the air quality. The results provide a scientific basis for understanding the mechanism between binary typhoons and aerosol air pollution and enable more accurate pollution alerts to be made during typhoons.

Лазерный контроль среднего объемно-поверхностного диаметра частиц для оценки параметров аэрозольного загрязнения атмосферы

Aerosol air pollution is one of the most dynamic factors of the environmenal technogenic transformation. The danger degree of the aerosol particles increases in air with their sizes reduction therefore the dust disperse composition has the great hygienic value and in the working zone air and the dust disperse composition at the enterprise border — on health of the population of these territories are the important characteristic for its It has led to the introduction of new ecological standards for mass concentration of the particles with a diameter less than 10 μ (PM10) and particles with a diameter less than 2,5 μ (PM2,5). impact assessment on health of the enterprise employees and the population of near territories. The laser methods using for the assessment of parameters of aerosol emissions and extent of their impact on the environment have been introduced in this article. The modified spectral transparency method is the best of all and suitable for determination of the average size and concentration of disperse particles. The physical model of this method is based on interaction of monochromatic laser radiation with the polydisperse aerosol by Mie’s theories and maintaining invariancy of the average factor of the extinction efficiency concerning the type of the of particles size distribution function with using of the concept of particles average volume and superficial diameter. The optical density measurement of the disperse aerosol is performed at the same time, on several wavelengths, and the average factors of the extinction efficiency for these laser radiation wavelengths can be derived from the experimental data. This method has rather simple hardware realization and allow to diagnose flows of high optical density (that is characteristic of technogenic aero disperse flows).

Ground-based network observation using Mie–Raman lidars and multi-wavelength Raman lidars and algorithm to retrieve distributions of aerosol components

We improved two-wavelength polarization Mie-scattering lidars at several main sites of the Asian dust and aerosol lidar observation network (AD-Net) by adding a nitrogen Raman scatter measurement channel at 607nm and have conducted ground-based network observation with the improved Mie–Raman lidars (MRL) in East Asia since 2009. This MRL provides 1α+2β+1δ data at nighttime: extinction coefficient (α532), backscatter coefficient (β532), and depolarization ratio (δ532) of particles at 532nm and an attenuated backscatter coefficient at 1064nm (βat,1064). Furthermore, we developed a Multi-wavelength Mie-Raman lidar (MMRL) providing 2α+3β+2δ data (α at 355 and 532nm; β at 355 and 532; βat at 1064nm; and δ at 355 and 532nm) and constructed MMRLs at several main sites of the AD-Net. We identified an aerosol-rich layer and height of the planetary boundary layer (PBL) using βat,1064 data, and derived aerosol optical properties (AOPs, for example, αa, βa, δa, and lidar ratio (Sa)). We demonstrated that AOPs cloud be derived with appropriate accuracy. Seasonal means of AOPs in the PBL were evaluated for each MRL observation site using three-year data from 2010 through 2012; the AOPs changed according to each season and region. For example, Sa,532 at Fukue, Japan, were 44±15sr in winter and 49±17 in summer; those at Seoul, Korea, were 56±18sr in winter and 62±15sr in summer. We developed an algorithm to estimate extinction coefficients at 532nm for black carbon, dust, sea-salt, and air-pollution aerosols consisting of a mixture of sulfate, nitrate, and organic-carbon substances using the 1α532+2β532 and 1064+1δ532 data. With this method, we assume an external mixture of aerosol components and prescribe their size distributions, refractive indexes, and particle shapes. We applied the algorithm to the observed data to demonstrate the performance of the algorithm and determined the vertical structure for each aerosol component.

The Asian Dust and Aerosol Lidar Observation Network (AD-NET): Strategy and Progress

We have operated a ground-based lidar network AD-Net using dual wavelength (532, 1064nm) depolarization Mie lidar continuously and observed movement of Asian dust and air pollution aerosols in East Asia since 2001. This lidar network observation contributed to understanding of the occurrence and transport mechanisms of Asian dust, validation of chemical transport models, data assimilation and epidemiologic studies. To better understand the optical and microphysical properties, externally and internally mixing states, and the movements of Asian dust and airpollution aerosols, we go forward with introducing a multi-wavelength Raman lidar to the AD-Net and developing a multi-wavelength technique of HSRL in order to evaluate optical concentrations of more aerosol components. We will use this evolving AD-Net for validation of Earth-CARE satellite observation and data assimilation to evaluate emissions of air pollution and dust aerosols in East Asia. We go forward with deploying an in-situ instrument polarization optical particle counter (POPC), which can measure size distributions and non-sphericity of aerosols, to several main AD-Net sites and conducting simultaneous observation of POPC and lidar to clarify internally mixed state of Asian dust and air pollution aerosols transported from the Asian continent to Japan.

A study of morbidity on the territory of the municipality of stara zagora in connection with air pollution aerosols lead

Within 5 years (2009-2013) surveyed the annual dynamics of the concentration of one of the major air pollutants in the municipality of Stara Zagora - lead aerosols and their impact on public health. In the process of monitoring parallel analyzed the average monthly levels of this pollutant. The problem of lead poisoning associated with heavy environmental pollution (primarily atmospheric air) is most relevant to large industrial cities. In the current environmental situation, the best indicator of the negative impact of lead pollution on the body is the level of morbidity of the population, which depends on the concentration of lead particulate pollutants in ambient air. When evaluating relationship pollution-morbidity on the outcome of hospitalization for different age groups the correlation dependences between the average annual concentration of lead aerosols and various diseases. For this purpose were formed correlation matrix for all types of registered diseases (associated with the impact of lead aerosols on the body), according 10 the International classification of diseases for 3 age groups: 0 to 17 years, 18 years and older and the total population. The analytical data show a significant dependence of the development of several classes of diseases as a result of exposure to toxic lead aerosols contained in the air. In the age group from 0 to 17 years the effect of pollution by lead compounds set the highest correlation dependence diseases of the skin and subcutaneous tissue, registered at the hospital, and for a group of 18 years and more with diseases of the blood and blood-forming organs. Lead aerosols and dust particles have an additive effect on the diseases of the circulatory system in the group of the total population in the municipality of Stara Zagora.

Analysis of Vertical Profile of Particulates Dispersion in Function of the Aerodynamic Diameter at a Congested Road in Catania

During last decades the aerosol concentrations have increased causing a further restriction of current regulations. The World Health Organization (WHO) has estimated that the impact of aerosol air pollution to health, especially for PM10 and PM2.5, constitutes one of the main preoccupations in terms of the interaction health-environment. Since last report about air quality in Europe, published by European Environment Agency (EEA), it is evident that the 90% of citizens of European citiesis exposed to very dangerous pollution levels and, furthermore, it has been estimated that between 2009 and 2011 the 96% of population of main European cities was subjected to aerosol levels greater than the limits imposed by WHO. One of the main tasks of UE, within 2020, is aiming at reducing the pollution with a consequent improvement of its effects to health. In this work it was analyzed experimentally the distribution of aerosol particles in function of the sampling height and the aerodynamic diameters of particles. There were used portable samplers. The experimental campaign was conduced during rush hours in a high congested road of Catania at three different heights. Thanks to analysis of variance (ANOVA) it was possible to verify the interaction between the aerodynamic diameter of particles and the considered sampling heights.

Association between pulmonary function and daily levels of sand dust particles assessed by light detection and ranging in schoolchildren in western Japan: A panel study

BackgroundAn important aspect of sand dust emissions in association with respiratory disorders is the quantity of particulate matter. This is usually expressed as particulate matter less than 10 μm (PM10) and 2.5 μm (PM2.5). However, the composition of PM10 and PM2.5 varies. Light detection and ranging is used to monitor sand dust particles originating in East Asian deserts and distinguish them from air pollution aerosols. The objective of this study was to investigate the association between the daily levels of sand dust particles and pulmonary function in schoolchildren in western Japan. MethodsIn this panel study, the peak expiratory flow (PEF) of 399 schoolchildren was measured daily from April to May 2012. A linear mixed model was used to estimate the association of PEF with the daily levels of sand dust particles, suspended particulate matter (SPM), and PM2.5. ResultsThere was no association between the daily level of sand dust particles and air pollution aerosols, while both sand dust particles and air pollution aerosols had a significant association with SPM and PM2.5. An increment of 0.018 km−1 in sand dust particles was significantly associated with a decrease in PEF (−3.62 L/min; 95% confidence interval, −4.66 to −2.59). An increase of 14.0 μg/m3 in SPM and 10.7 μg/m3 in PM2.5 led to a significant decrease of −2.16 L/min (−2.88 to −1.43) and −2.58 L/min (−3.59 to −1.57), respectively, in PEF. ConclusionsThese results suggest that exposure to sand dust emission may relate to pulmonary dysfunction in children in East Asia.

Ceilometer calibration for retrieval of aerosol optical properties

Ceilometers are durable compact backscatter lidars widely used to detect cloud base height. They are also useful for measuring aerosols. We introduced a ceilometer (CL51) for observing dust in a source region in Mongolia. For retrieving aerosol profiles with a backscatter lidar, the molecular backscatter signal in the aerosol free heights or system constant of the lidar is required. Although the system constant of the ceilometer is calibrated by the manufacturer, it is not necessarily accurate enough for the aerosol retrieval. We determined a correction factor, which is defined as the ratio of true attenuated backscattering coefficient to the measured attenuated backscattering coefficient, for the CL51 ceilometer using a dual-wavelength Mie-scattering lidar in Tsukuba, Japan before moving the ceilometer to Dalanzadgad, Mongolia. The correction factor determined by minimizing the difference between the ceilometer and lidar backscattering coefficients was approximately 1.2±0.1. Applying the correction to the CL51 signals, the aerosol optical depth (AOD) agreed well with the sky-radiometer AOD during the observation period (13–17 February 2013) in Tsukuba (9×10−3 of mean square error). After moving the ceilometer to Dalanzadgad, however, the AOD observed with the CL51 (calibrated by the correction factor determined in Tsukuba) was approximately 60% of the AErosol RObotic NETwork (AERONET) sun photometer AOD. The possible causes of the lower AOD results are as follows: (1) the limited height range of extinction integration (<3km); (2) change in the correction factor during the ceilometer transportation or with the window contamination in Mongolia. In both cases, on-site calibrations by dual-wavelength lidar are needed. As an alternative method, we showed that the backward inversion method was useful for retrieving extinction coefficients if the AOD was larger than 1.5. This retrieval method does not require the system constant and molecular backscatter signals, and can be applied to severe dust and air pollution aerosol cases in East Asia.

Detection of internally mixed Asian dust with air pollution aerosols using a polarization optical particle counter and a polarization-sensitive two-wavelength lidar

East Asia is a unique region where mineral dust (Asian dust) sources are located near urban and industrial areas. Asian dust is often mixed with air pollution aerosols during transportation. It is important to understand the mixing states of Asian dust and other aerosols, because the effects on the environment and human health differ depending on the mixing state. We studied the mixing states of Asian dust using a polarization particle counter (POPC) that measures the forward scattering and the two polarization components of backscattering for single particles and a polarization-sensitive (532nm) two-wavelength (1064nm and 532nm) lidar. We conducted the simultaneous observations using the POPC and the lidar in Seoul from March to December 2013 and captured the characteristics of pure Asian dust and internally mixed polluted Asian dust. POPC measurements indicated that the density of large particles was lower in polluted Asian dust that transported slowly over the polluted areas than in pure Asian dust that transported quickly from the dust source region. Moreover, the backscattering depolarization ratio was smaller for all particle sizes in polluted dust. The optical characteristics measured using the lidar were consistent with the POPC measurements. The backscattering color ratio of polluted dust was comparable to that of pure dust, but the depolarization ratio was lower for polluted dust. In addition, coarse non-spherical particles (Asian dust) almost always existed in the background, and the depolarization ratio had seasonal variation with a lower depolarization ratio in the summer. These results suggest background Asian dust particles are internally mixed in the summer.

Analysis of dust events in 2008 and 2009 using the lidar network, surface observations and the CFORS model

The Asian dust events in 2008 (May 24–June 4 in 2008) and in 2009 (March 12–25, October 13–26, and December 15–28 in 2009) were analyzed with the lidar network observations, surface observations in China, Korea, Japan, and Mongolia, and with the chemical transport model CFORS. Transport of Asian dust and mixing of dust with air pollution aerosols were studied. The event of May 24 to June 4 in 2008 was a significant event unusually late in the spring dust season. The dust event of March 12–25, 2009 was an interesting example of elevated dust layer, and transport of dust from the elevated dust layer to the ground by the boundary layer activity was observed with the lidars and surface observations in Japan. The concentration of air pollution aerosols was relatively high during the dust event, and the results suggest that vertical structure as well as transport path is important for the mixing of dust and air pollution aerosols. The dust events in October and December 2009 were examples of dust events in autumn and winter. The online mode CFORS reproduced the observation data generally well, except for the event of May 24 to June 4 in 2008. The results of the fourdimensional variational assimilation of the lidar network data reproduced the dust concentration in Korea and Japan reasonably in that event.