Chemical Composition Of Atmospheric Aerosols Research Articles

Rapid growth and high cloud-forming potential of anthropogenic sulfate aerosol in a thermal power plant plume during COVID lockdown in India

The COVID lockdown presented an interesting opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event resulting from distinct meteorological conditions. This event was marked by rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant in Southern India. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions provides important new clues to delineate the contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing.

ХИМИЧЕСКИЙ СОСТАВ АТМОСФЕРНЫХ ВЫПАДЕНИЙ НА ТЕРРИТОРИИ БАЙКАЛЬСКОГО ГОСУДАРСТВЕННОГО ПРИРОДНОГО БИОСФЕРНОГО ЗАПОВЕДНИКА (ВОСТОЧНОЕ ПОБЕРЕЖЬЕ ЮЖНОГО БАЙКАЛА)

The results of studying the chemical composition of atmospheric aerosol, precipitation, and snow cover on the territory of the Baikal State Biospherical Nature Reserve during 2017-2021 are presented. The principal ions in atmospheric aerosol and precipitation were sulfates and ammonium and those for snow cover were sulfates, nitrates, and calcium. The series of detailed simulations with the HYSPLIT model and the methods for statistical data processing (ArcGIS 10.2 and RStudio software) enable the identification of natural and anthropogenic groups of sources affecting the chemical compound of atmospheric deposition on the eastern coast of Lake Baikal. Based on snow survey data, the accumulation of the substances, which are the indicators of anthropogenic load, in the snow cover of the Baikal State Biospherical Nature Reserve was evaluated.

Air quality modeling in the city of Marrakech, Morocco using a local anthropogenic emission inventory

Exposure to high levels of suspended particles, and particularly dust, has been associated with increased risk of morbidity and premature mortality. The city of Marrakech is situated at a distance of only 560 km from the Sahara desert, the major dust source in the world, leading to an atmosphere rich in particulate matter all year round. In this study, we use for the first-time local scale information on anthropogenic emissions in the city of Marrakech and conduct urban-scale chemistry-transport model simulations with the CHIMERE-WRF coupled system. We compare simulated airborne particles of diameter lower to 10 μm (PM10), NO2 and O3 concentrations against surface in-situ measurements and quantify the added value of the local inventory compared to the state-of-the-art global anthropogenic emission dataset (CAMS-GLOB_ANT). We show that correlation with measurements increases and the bias decreases in all cases (pollutants, seasons and monitor sites). The major component of summertime PM10 composition is dust particles, whereas in winter PM10 consists mainly of primary organic aerosol. Comparison between simulated and observed aerosol optical depth suggests that the model reproduces accurately most of the observed summertime dust plumes. PM10 simulated concentrations are closer to in-situ surface measurements during summer than during winter with an overestimation of 13% in summer versus an underestimation of 37% in winter. Finally, we show how the Atlas range blocks at some extent the import of dust plumes in the region and the export of local air-pollution to the surrounding area leading to ozone formation at high altitude.Modeling is an important activity to predict air-quality in Africa, where monitor networks are scarce. Our results highlight the necessity of using fine scale, local information on anthropogenic emissions to assess air-quality and in particular to (i) quantify the chemical composition of atmospheric aerosol; ii) compare the relative role of dust transport compared to locally emitted or formed suspended particles and iii) provide evidence of ozone formation at high altitude.

Variability of the Chemical Composition of the Atmospheric Aerosol in the Coastal Zone of the Southern Basin of Lake Baikal (East Siberia, Russia)

The role of the atmosphere in the formation of the chemical composition and quality of water in Lake Baikal and its tributaries has been increasing in recent years. In this regard, studies of the chemical composition of the constituents of the atmosphere have an important practical application. In 2020 and 2021, we studied the chemical composition of atmospheric aerosol, one of the indicators of air pollution, in the atmosphere of the coastal zone of the southern basin of Lake Baikal compared to the data from previous years. The studies were carried out in the summer on the southwestern (Bolshiye Koty) and southeastern coast (Boyarsky). In the absence of smoke in the aerosol on the southwest coast, the concentrations of NH4+, NO3− and SO42− ions prevailed. The mean total concentration of ions at the Bolshiye Koty research station was 2.08 ± 1.26 μg/m3. The appearance of smog contributed to the growth of the total ionic concentration in the aerosol on the southwest coast to 6.4 μg/m3 in 2020 and to 17.6 μg/m3 in 2021. On the southeast coast, the minimum concentration of the total amount of ions was 3.3 μg/m3. The concentrations of Ca2+, Na+, K+, Cl−, and SO42− ions prevailed in the aerosol. Under the influence of smog, the total amount of ions increased to 34.1 μg/m3 in 2020 and to 18.6 μg/m3 in 2021. In periods of intense smoke, NH4+ and SO42− became the dominant ions in the aerosols at both stations. The contribution of NO3− ions increased. Although the effect of natural factors is periodic, they contribute significantly to the change in the chemical composition of atmospheric aerosol.

The influence of agriculture on the chemical composition of aerosols in the coastal zone of the Southern Baltic Sea (Gdynia)

In order to improve soil quality, size, and appearance of plants, various types of fertilizers are used in Poland. They are rich in nitrogen, phosphorus, calcium, and potassium. Plants are fertilized before sowing, during germination, and during crop growth. Such agricultural activity can have a negative effect on the chemical composition of atmospheric aerosols, which can be transported with air masses far away from the agricultural sources regions. The aim of the research was to estimate the influence of agriculture on the chemical composition of aerosols of various sizes (<0.45 to 10 µm) in the atmosphere of the coastal zone of the Baltic Sea. The samples were collected in Gdynia, from 11/05/2016 to 17/08/2016, only outside traffic hours (10:00 a.m. - 3:00 p.m.) and only when air masses were transported from over agricultural areas. Aerosols were collected using Tisch Environmental high-flow impactor. The ions (NO3?, PO43-, K+, Ca2+) were determined by Metrohm ion chromatography (881 Compact IC pro). The obtained results allowed us to conclude that the highest mean concentrations of NO3?, K+, Ca2+occurred in aerosols below 0.45 µm in diameter (0.26, 0.04 and 5.85 µg·m-3, respectively). Phosphates showed the highest average concentration (0.191 µg·m-3) in aerosols with a diameter from 1.5 to 3.0 µm. The concentration of calcium and nitrates was the highest in the days when advection from Western Kashubia was dominant. In turn, the highest concentrations of phosphates and potassium occurred on the days when air masses were transported from Vistula ?u?awy. All episodes occurred in the spring when agricultural activity related to fertilizing farmland was the highest and the average wind speed was lower than 5 m·s-1, which indicates local to the regional origin of the analyzed compounds in aerosols.

Chemical Composition of Atmospheric Aerosol in the Arctic Region and Adjoining Seas along the Routes of Marine Expeditions in 2018–2019

We consider the chemical composition (ions, elements, and polycyclic aromatic hydrocarbons) of atmospheric aerosol in different regions of the North Atlantic, European and Russian parts of the Arctic Ocean, and northern latitude and Far East seas. The studies were carried out onboard marine ships along their cruising routes (RV Akademik Tryoshnikov, RV Akademik Mstislav Keldysh, and RV Professor Multanovsky). The air samples were collected using the method accepted in the international networks operating under the Acid Deposition Monitoring Network in East Asia (EANET) and European Monitoring and Evaluation Programme (EMEP). The average sum of ion concentrations and the concentrations of individual ions in the aerosol over the seas in the North Atlantic and in the European part of the Arctic Ocean is consistent with measurements in the Laptev and Kara Seas in 2018 and 2019. The high concnetrations of PAHs in aerosol in seas and the Arctic Ocean in the central part of the Russian Arctic coincide with high concentrations of ions and trace elements in the aerosol composition. A difference is noted in the distribution of concentrations of trace elements in aerosol composition between seas of the North Atlantic and central region of the Russian Arctic, which possibly points to different sources of these components.

Peat burning – An important source of pyridines in the earth atmosphere

Studies of the chemical composition of atmospheric aerosols, rain water and snow in various regions of the globe quite often show the presence of pyridine and a number of its low mass derivatives. Nevertheless, the sources of those compounds in the environment have not yet been established and definitely require elucidation, supported by reliable experimental results. In the present work the chemical composition of peat combustion products as one of the important sources of atmospheric aerosol emission is studied by two-dimensional gas chromatography – high-resolution mass spectrometry with a focus on the detection of pyridine derivatives. Twenty-five compounds of this class were reliably identified and quantified in laboratory experiments on peat burning. Among them 3-hydroxypyridine predominates, while the rest analytes are mostly represented by alkyl derivatives: pyridine, 2-methylpyridine, 3-methylpyridine, 2,5-dimethylpyridine, 2,6-dimethylpyridine, 2-ethylpyridine, lutidines (in order of decreasing concentration). The distribution of these combustion products coincides with that obtained earlier in environmental studies carried out in Arctic, Central Russia and France. The experiments on peat thermal decomposition by pyrolysis GC-MS demonstrated that the maximum concentrations as well as the number of detected analytes were found under conditions of oxygen lack and a temperature of about 500 °C, i.e. characteristic conditions of peat wildfires. The observed levels of pyridines’ emission recalculated on the peat dry weight exceeded 200 mg kg−1. Considering hundreds of millions tons of peat burning in megafires over 20,000 tons of pyridines penetrate the Earth atmosphere annually. The obtained results allow concluding that peat burning may be the major and still underestimated source of pyridine and lower alkylpyridines in the Earth atmosphere.

Chemical composition of atmospheric aerosol in the Arctic region along the routes of the research cruises in 2018-2019

Chemical composition of atmospheric aerosol in the Arctic region along the routes of the research cruises in 2018-2019

Diesel Soot and Amine-Containing Organic Sulfate Aerosols in an Arctic Oil Field.

The rapid decrease in Arctic sea ice is motivating development and increasing oil and gas extraction activities. However, few observations of these local Arctic emissions exist, limiting the understanding of impacts on atmospheric composition and climate. To address this knowledge gap, the chemical composition of atmospheric aerosols was measured within the North Slope of Alaska oil fields during August and September 2016 using an aerosol time-of-flight mass spectrometer (ATOFMS) and a time-of-flight aerosol chemical speciation monitor (ToF-ACSM). Plumes from oil and gas extraction activities were characterized by soot internally mixed with sulfate (matching diesel soot) and organic carbon particles containing aminium sulfate salts. Sea spray aerosol at the coastal site was frequently internally mixed with sulfate and nitrate, from multiphase chemical processing from elevated NOx and SO2 within the oil field. Background (nonplume) air masses were characterized by aged combustion aerosol. No periods of "clean" (nonpolluted) Arctic air were observed. The composition of the nonrefractory aerosol measured with the ACSM was similar during plume and background periods and was consistent with the mass concentrations of nonrefractory particles measured by ATOFMS. Two ultrafine aerosol growth events were observed during oil field background periods and were correlated with fine mode amine-containing particles.

ToF‐SIMS analysis of chemical composition of atmospheric aerosols in Beijing

Atmospheric aerosols collected from each season in urban Beijing have been studied using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The chemical composition of atmospheric aerosol particles during various atmospheric pollution levels was analyzed and distinguished by principal component analysis (PCA). The differences and sources of the components of the aerosol particles were explored. The results showed that the fine particulate matter from heavily polluted days mainly consists of inorganic salts and organic compounds, such as hydrocarbons, nitrogen‐ or sulfur‐containing hydrocarbons, and their oxides. Samples collected from clean days in the four seasons were also analyzed. Only the samples collected in spring showed a significant difference from the other three seasons. We concluded that the main source of pollution in the Beijing urban area was fossil fuel combustion from motor vehicles.

Col Margherita Observatory: A background site in the Eastern Italian Alps for investigating the chemical composition of atmospheric aerosols

The chemical composition of atmospheric aerosol collected at the Col Margherita Atmospheric Observatory (46° 22ˈ 0.059ˈˈ N, 11° 47ˈ 30.911ˈˈ E, 2543 m a.s.l.) was investigated during spring and summer 2018. This is the first study of this area and should lead to a better understanding of the aerosol chemical composition in the Southern slope of the Eastern Italian Alps, with the aim of proposing this high altitude site as a background station. Aerosol samples were analyzed to determine several water soluble components (Cl−, Br−, I−, NO3−, SO42−, K+, Mg2+, Na+, NH4+, Ca2+), organic acids (methanesulfonic acid and C2–C7 carboxylic acids), monosaccharides, alcohol-sugars, levoglucosan and its isomers, sucrose, phenolic compounds, free L- and D-amino acids and photo-oxidation products of α-pinene (cis-pinonic acid and pinic acid). The majority of the mass concentration is explained by ionic species, but the other investigated compounds allow us to study other processes or identify the potential sources. Carboxylic acids and photochemical products of α-pinene were used to study photochemical or oxidative processes. Biomass burning input was evaluated using two specific classes of biomarkers: anhydrosugars and phenolic compounds, while biogenic inputs were studied using sugars and free amino acids. None of these water soluble organic compounds have been properly investigated previously in alpine sites because their concentrations in aerosol are very low.

Impact of marine and continental sources on aerosol characteristics using an on-board SPAMS over southeast sea, China.

The chemical composition of atmospheric aerosols was characterized using an on-board single particle aerosol mass spectrometer (SPAMS) over the Southeast China Sea. High-time-resolution observation of marine aerosols was carried out to clarify the source of aerosols and the interaction of marine and continental aerosols. Atmospheric aerosols were determined by the interaction of continental and marine sources over coastal area. Aerosols from continental sources flux into sea surfaces through deposition or diffusion, which results in the rapid decrease of continental aerosols. Five main subtypes of carbonaceous particles are identified as C_Al-Si, C_V-Ni, C_S, C_K, and C_secondary to clarify the impact of marine and continental sources on atmospheric aerosols. High fraction of C_Al-Si and C_secondary is present over XA (Xiamen anchorage), accounting for 23.8% and 18.6% of total carbonaceous particles. Contrarily, the relative percentage of C_S increases as the distance from land to sea increases. The influence of continental aerosols declines, while the contribution of marine aerosols increases as the distance from land to sea increases. Air masses in XA, LSA (land to sea area), SLA (sea to land area), and SA (sea area) were all from ocean during the observation period, resulting in low relative fraction of continental aerosols in SLA, SA, and LSA. High-time-resolution measurement is useful to understand aerosol source types and the impact of marine and continental sources on marine atmosphere aerosols.

Investigation of Chemical Composition of Atmospheric Aerosol in Ulaanbaatar During 2005–2014

Results from investigating atmospheric aerosols in Ulaanbaatar (Mongolia) 2005–2014 are presented. It is found that the largest sources of suspended particles are represented by fuel combustion and the concomitant exhaust gases, thermal power generation, industrial facilities and mineral dust transport; the main components of aerosol particles are SO 4 2- , NO 3 - , Cl–, NH 4 + , Ca2+ and Na+. It is determined that in the wintertime, as a result of an increase in fuel consumption, calm weather and orographic characteristics of topography which contribute to accumulation of contaminants in the urban atmosphere, the average sum of ions increases to 43.9–114.6 μg/m3 against 7.44–18.48 μg/m3 during a warm season. Interannual differences in aerosol composition were noted; the total ion content averaged 43.9 μg/m3 during December 2011, 114.6 μg /m3 during December 2012, 68.7 μg/m3 during December 2013, and 64.7 μg/m3 during December 2014. It was found that the concentration of the sum of ions in the aerosol during the winter period is by a factor of 6 higher than during the summer. The highest exceedance of the concentrations was observed for the alkaline earth ions Na+, K+, Ca2+ and Mg2+ (by a factor of more than 20) forming part of the ash components. There is a difference in the chemical composition of the aerosol sampled in the center of the city and on its outskirts. It is established that the aerosol composition and concentration in Ulaanbaatar during the winter period are comparable the aerosol composition in the industrial cities of China.

Compositional variability of the aerosols collected in Sfax (Central Tunisia)

In order to assess the variability of the chemical composition of atmospheric aerosols in Central Tunisia and determine their origin, 140 aerosols samples were collected from March 2015 to April 2016 in the industrial city of Sfax. The particles collected on membranes were submitted to X-ray Fluorescence analysis and the concentrations of sixteen elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn and Pb) quantified. According to the values of their enrichment factors (EF) relative to the composition of the Earth crust and of sea-salt, these elements can be classified in three main categories: 1) crustal (Al, Si, Fe, Ca, Ti, Ni, P, and Mn), 2) marine (Na, Cl), and 3) anthropogenic (S, Zn, Cu, and Pb). Then, we apply the Positive Matrix Factorization (PMF) to the dataset in order to assess the profiles and contributions of the main sources of the aerosol. Beside the marine and anthropogenic factors, 3 other factors are necessary to represent the mineral dust component, which emphasizes the diversity of its sources. In usual conditions, the dominating factor (Ca-Dust) is enriched in both Ca and Mg, and is most probably emitted from regional sources. Its contribution to the atmospheric aerosol loading usually lies between 0.75 and 6.37μg/m3(10th and 90th percentiles, respectively) but can peak at 9.28μg/m3. The second factor, simply referred to as the Dust factor, corresponds to dust emitted by, and transported from, more distant desert sources. During the massive advection events, its contribution to the aerosol loading in Sfax can be above 100μg/m3. Finally, the outdoor deposits of the residues of the local phosphate industry are an occasional source of P-enriched mineral dust (P-Dust) and some heavy metals (Cu, Ni, Zn, Pb). However, their contribution to the aerosol concentration is usually low (0.12–0.25μg/m3) and does not seem to constitute an important source of contamination.

Aerosol in the atmosphere of the Baikal region: history and contemporary researches

The results of long-term studies (1995-2017) of the physical properties and chemical composition of atmospheric aerosol in the Baikal region are considered. These studies are important for understanding the role of the atmosphere in the formation of the chemical composition and quality of the waters of Baikal and its inflows. Over the past two decades, Limnological Institute SB RAS (Irkutsk, Russia) have conducted various joint studies of the characteristics of atmospheric aerosol with Russian and foreign groups. The chemical composition, biological component, size distribution, spatial distribution and aerosol sources over the lake were investigated. The interannual variability of the main chemical compounds in the aerosol was estimated. So, over the period studied, there was a gradual decrease observed in the concentrations of the main ions in the aerosol composition: in Irkutsk by 2.1 times, Listvyanka - by 4.0 times, at the background site of Mondy - by 3.5 times. In addition to quantitative changes, there is a change in the ratio of the main ions in the aerosol at Listvyanka site (south-west coast of Lake Baikal) and at the background site of Mondy. Upon condition of no external influences the content of the main ions in the aerosol on the surface layer of Lake Baikal is signifcantly lower (0.33-5.2 μg·m-3) than during of extreme conditions (2.2-5.2 μg·m-3). Forest fres near Baikal causean increase of the concentrations of Na+, K+, NH4+, Cl-, and NO3- ions in Baikal aerosols. Componentsof soil-erosion origin (Al, Fe, Zn, Cr, Ba) dominate in the elemental composition of the aerosol. Theirconcentration increases during forest fres up to 1.4 - 6 times at average. The flows of sulfur and nitrogen, the main acidifying components, differ in different years of observations both at the monitoring sites and over the surface of Lake Baikal.

Investigation of chemical composition of atmospheric aerosol in Ulaanbaatar during 2005–2014

Investigation of chemical composition of atmospheric aerosol in Ulaanbaatar during 2005–2014

How much information do extinction and backscattering measurements contain about the chemical composition of atmospheric aerosol?

Abstract. We theoretically and numerically investigate the problem of assimilating multiwavelength lidar observations of extinction and backscattering coefficients of aerosols into a chemical transport model. More specifically, we consider the inverse problem of determining the chemical composition of aerosols from these observations. The main questions are how much information the observations contain to determine the particles' chemical composition, and how one can optimize a chemical data assimilation system to make maximum use of the available information. We first quantify the information content of the measurements by computing the singular values of the scaled observation operator. From the singular values we can compute the number of signal degrees of freedom, Ns, and the reduction in Shannon entropy, H. As expected, the information content as expressed by either Ns or H grows as one increases the number of observational parameters and/or wavelengths. However, the information content is strongly sensitive to the observation error. The larger the observation error variance, the lower the growth rate of Ns or H with increasing number of observations. The right singular vectors of the scaled observation operator can be employed to transform the model variables into a new basis in which the components of the state vector can be partitioned into signal-related and noise-related components. We incorporate these results in a chemical data assimilation algorithm by introducing weak constraints that restrict the assimilation algorithm to acting on the signal-related model variables only. This ensures that the information contained in the measurements is fully exploited, but not overused. Numerical tests show that the constrained data assimilation algorithm provides a solution to the inverse problem that is considerably less noisy than the corresponding unconstrained algorithm. This suggests that the restriction of the algorithm to the signal-related model variables suppresses the assimilation of noise in the observations.

Simultaneous Measurement of CCN Activity and Chemical Composition of Fine-Mode Aerosols at Noto Peninsula, Japan, in Autumn 2012

Size resolved CCN activity and bulk chemical composition of atmospheric aerosols in the submicrometer size range were measured at Noto Ground-based Research Observatory (NOTOGRO), facing the Sea of Japan at the tip of Noto Peninsula, in autumn 2012. In the atmospheric measurement, the CCN efficiency spectra, where the CCN number fraction is plotted against the diameter of aerosols, were obtained for four different supersaturation (SS) conditions. The hygroscopicity parameter κ, which depends on the chemical composition of aerosols, was estimated from analysis of the CCN spectra. The CCN activation diameters of ambient aerosols were clearly larger than those of pure ammonium sulfate under all SS conditions. The bulk chemical composition derived by an aerosol chemical speciation monitor (ACSM) also indicated the significant mass fraction of organics in the submicrometer size range. The relationship between the estimated κ values and the CCN activation diameters suggests that organics contribute the aerosol mass especially in the size range of less than 100 nm. The contribution of organics observed in this study was more apparent than those of other sites in East Asia. The mass concentrations and chemical compositions of the aerosols varied with trajectory pathway, which caused large fluctuations in κ values especially at higher SS conditions. The negative correlations between organic mass fraction and the diameters of cloud droplet diameters were observed under low SS conditions (0.13% and 0.25%), suggesting that less-hygroscopic organics, that can suppress the initial growth rates of cloud droplets, were included during the periods of large organic mass concentrations.

Measurement of aerosol effective density by single particle mass spectrometry

Single particle mass spectrometry has been widely used to determine the size and chemical compositions of atmospheric aerosols; however, it is still rarely used for the microphysical properties measurement. In this study, two methods were developed for determining aerosol effective density by a single particle aerosol mass spectrometer (SPAMS). Method I retrieved effective density through comparison between measured light scattering intensities and Mie theoretical modelled partial scattering cross section. Method II coupled a differential mobility analyzer (DMA) with SPAMS to simultaneously determine the electric mobility and vacuum aerodynamic diameter, and thus the effective density. Polystyrene latex spheres, ammonium sulfate and sodium nitrate were tested by these methods to help validate their effectiveness for determining the aerosol effective density. This study effectively extends SPAMS measurements to include particle size, chemical composition, light scattering, and effective density, and thus helps us better understand the environment and climate effects of aerosols.

Effect of biomass burning over the western North Pacific Rim: wintertime maxima of anhydrosugars in ambient aerosols from Okinawa

Abstract. Biomass burning (BB) largely modifies the chemical composition of atmospheric aerosols on the globe. We collected aerosol samples (TSP) at Cape Hedo, on subtropical Okinawa Island, from October 2009 to February 2012 to study anhydrosugars as BB tracers. Levoglucosan was detected as the dominant anhydrosugar followed by its isomers, mannosan and galactosan. We found a clear seasonal trend of levoglucosan and mannosan with winter maxima and summer minima. Positive correlation was found between levoglucosan and nss-K+ (r = 0.38, p < 0.001); the latter is another BB tracer. The analyses of air mass trajectories and fire spots demonstrated that the seasonal variations of anhydrosugars are caused by long-range transport of BB emissions from the Asian continent. We found winter maxima of anhydrosugars, which may be associated with open burning and domestic heating and cooking in northern and northeastern China, Mongolia and Russia and with the enhanced westerly winds. The monthly averaged levoglucosan / mannosan ratios were lower (2.1–4.8) in May–June and higher (13.3–13.9) in November–December. The lower values may be associated with softwood burning in northern China, Korea and southwestern Japan whereas the higher values are probably caused by agricultural waste burning of maize straw in the North China Plain. Anhydrosugars comprised 0.22% of water-soluble organic carbon (WSOC) and 0.13% of organic carbon (OC). The highest values to WSOC (0.37%) and OC (0.25%) were found in winter, again indicating an important BB contribution to Okinawa aerosols in winter. This study provides useful information to better understand the effect of East Asian biomass burning on the air quality in the western North Pacific Rim.