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An extensive study was conducted to comprehensively assess simultaneous quantitative estimates of biomass burning organic carbon (OC-BB) within fine particulate matter (PM 2.5) across four distinct sites encompassing metropolitan and rural regions of Northeast Asia during the spring season. PM 2.5 samples were simultaneously collected in sites in Seoul and Seosan (SE: urban and SS: rural, Korea, respectively), Beijing (BJ: urban, China) and Ulaanbaatar (UB: urban, Mongolia), spanning from March to April 2022. The analysis of these samples aimed to quantify BB markers, including levoglucosan, mannosan, and K+, alongside OC. This analysis aimed to provide valuable insights into the impact and contribution of BB to PM 2.5 and OC. BB types were identified using levoglucosan/K+-BB and levoglucosan/mannosan ratios. In addition, our study focused on deriving an optimized OC/levoglucosan ratio, which is crucial for the accurate estimation of OC-BB concentrations. Moreover, an approach utilized in this study can be applied in other regions to estimate region-specific OC ∕ levoglucosan ratios for OC-BB. The contribution of OC-BB to total OC varied significantly across sites: SE (27 ± 17%), SS (60 ± 24%), BJ (5 ± 3%), and UB (51 ± 14%). Concentrations of levoglucosan and OC-BB were highest at UB and SS, indicating a greater impact of BB aerosols compared to SE and BJ. Cluster and potential source contribution function analyses showed that in SE, aerosols were influenced by BB originating from both the northwest and southwest directions. Conversely, in SS, the presence of aged, regional, and long-range transported aerosols from the northwest and south directions was observed. This study has the potential to assist in devising precise strategies aimed at mitigating BB, thus fostering improved air quality and environmental protection. • An optimized OC/levoglucosan ratio was developed for accurate estimation of OC-BB concentrations. • The impact of BB in Northeast Asia was quantitatively estimated using levoglucosan, mannosan, and K+ as tracers. • Hardwood, softwood, crops, and grass were the likely main sources of OC from BB in Northeast Asia. [ABSTRACT FROM AUTHOR]

Particulate matter with an aerodynamic diameter of 2.5 μm or less (PM 2.5) harbors a diverse microbial community. To assess the ecological dynamics and potential health risks associated with airborne microorganisms, it is crucial to understand the factors influencing microbial communities within PM 2.5. This study investigated the influence of abiotic parameters, including air pollutants, PM 2.5 chemical composition (water-soluble ions and organics), and meteorological variables, on microbial communities in PM 2.5 samples collected in Seoul during the spring season. Results revealed a significant correlation between air pollutants and water-soluble ions of PM 2.5 with microbial α-diversity indices. Additionally, air pollutants exerted a dominant effect on the microbial community structure, with stronger correlations observed for fungi than bacteria, whereas meteorological variables including temperature, pressure, wind speed, and humidity exerted a limited influence on fungal α-diversity. Furthermore, the results revealed specific water-soluble ions, such as SO 4 2−, NO 3 −, and NH 4 +, as important factors influencing fungal α-diversity, whereas K+ negatively correlated with both microbial α-diversity. Moreover, PM 2.5 microbial diversity was affected by organic compounds within PM 2.5 , with fatty acids exhibited a positive correlation with fungal diversity, while dicarboxylic acids exhibited a negative correlation with it. Furthermore, network analysis revealed direct links between air pollutants and dominant bacterial and fungal genera. The air pollutants exhibited a strong correlation with bacterial genera, such as Arthrospira and Clostridium , and fungal genera, including Aureobasidium and Cladosporium. These results will contribute to our understanding of the ecological dynamics of airborne microorganisms and provide insights into the potential risks associated with PM 2.5 exposure. [Display omitted] • Chemicals within PM 2.5 and gaseous pollutants strongly shape microbial communities. • Water-soluble ions are key factors influencing microbial α-diversity in PM 2.5. • Sugars positively, but DCAs negatively impact microbial α-diversity. • SO 4 2−, NO 3 −, and NH 4 + negatively influenced fungal α-diversity. • PM 2.5 , OC, EC, and CO closely associated with dominant genera. [ABSTRACT FROM AUTHOR]

The chemical and seasonal characteristics of fine particulates in Seoul, Korea, were investigated based on 24-h integrated PM2.5 measurements made over four 1-month periods in each season between October 2012 and September 2013. The four-season average concentration of PM2.5 was 37 μg m−3, and the major chemical components were secondary inorganic aerosol (SIA) species of sulfate, nitrate, and ammonium (49%), followed by organic matter (34%). The mass concentration and most of the chemical components of PM2.5 showed clear seasonal variation, with a winter-high and summer-low pattern. The winter-to-summer sulfate ratio and the winter organic carbon (OC)-to-elemental carbon (EC) ratio were unusually high compared with those in previous studies. Strong correlations of both the sulfate level and the sulfur oxidation ratio with relative humidity, and between water-soluble OC (WSOC) and SIA in winter, suggest the importance of aqueous phase chemistry for secondary aerosols. A strong correlation between non-sea salt sulfate and Na+ levels, a high Cl−/Na+ ratio, and an unusual positive correlation between the nitrogen oxidation ratio and temperature during the winter indicate the influence of transported secondary emission sources from upwind urban areas and from China across the Yellow Sea. Despite the absence of local forest fires and the regulation of wood burning, a high levoglucosan concentration and its correlations with OC and WSOC indicate that Seoul was affected by biomass burning sources in the winter. The unusually high water-insoluble OC (WIOC)-to-EC ratio in winter implies additional transported combustion sources of WIOC. The strong correlation between WIOC and levoglucosan suggests the likely influence of transported biomass burning sources on the high WIOC/EC ratio during the winter. [ABSTRACT FROM AUTHOR]

Abstract: Polycyclic aromatic hydrocarbons (PAHs) in both gas and total suspended particles were measured at Gosan, Jeju Island in Korea, a remote background site, for 15 days (March 29–April 12, 2002). During the sampling period, a severe three-day Asian dust (AD) event originating from Mongolia and northern China was observed throughout the Korean Peninsula and Jeju Island. In addition, pollution (PO) and normal (NO) periods were also identified based on the levels of anthropogenic pollutants. Despite a large difference of PM10 concentrations between the AD and PO periods, the levels of particulate PAHs in both periods were comparable (2.7±1.0 and 2.4±0.5ngm−3, respectively) since they were determined by the concentration of anthropogenic PM2.5 transported from industrial areas of China. In the AD period, the level of gaseous PAHs, which were mostly from local sources, was the lowest due to strong winds; the gas/particle partitioning was close to equilibrium as the effect of long-range transport was manifested. The results of backward air trajectories, correlation analysis, and diagnostic ratios show that long-range transport of particulate PAHs produced by coal/biomass burning in China could strongly affect the levels and patterns of PAHs at Gosan, Korea. [Copyright &y& Elsevier]

Nitrosamines and nitramines are groups of chemical compounds containing nitroso (N-NO) and nitro (N-NO 2) functional groups, respectively. They exert detrimental effects on our health. Simultaneous analysis of 7 nitrosamines and 3 nitramines present in atmospheric particulate matter with an aerodynamic diameter less than or equal to the nominal value of 2.5 μm (PM 2.5) at Seoul in the winter of 2018 was undertaken using gas chromatography/tandem mass spectrometry (GC/MS-MS). The daily average concentrations of nitrosamines and nitramines during the sampling period were 9.75 ± 17.77 ng/m3 (0.06–54.72 ng/m3) and 0.68 ± 0.56 ng/m3 (0.08–2.40 ng/m3), respectively. The concentrations of nitramines in the atmosphere were reported in this study for the first time and could not be compared. Among the nitrosamines, nitrosodi-methylamine (NDMA) concentrations observed in this study were high and comparable to that observed at the area with emission sources (Zonguldak, Turkey) and higher than that in an urban area (North Kensington, UK). Concentrations of other nitrosamines such as nitrosodi-ethylamine (NDEA), nitrosodi-butylamine (NDBA), nitroso-piperidine (NPIP), nitroso-pyrrolidine (NPYR), and nitrosodi-propylamine (NDPA) were similar to or lower than those noted in urban areas in the previous studies. In order to determine the relative importance of primary emissions and secondary reactions, statistical analyses such as correlation and multivariance analysis were carried out. Multivariance analysis results showed that secondary reaction might affect to the formation of the nitrosamines and nitramines in the atmosphere more than the primary emission. Furthermore , the high correlations of the nitrosamines and nitramines with HONO and NO supported the possibility of the high contribution of the secondary reactions producing the nitrosamines and nitramines. • 7 nitrosamines and 3 nitramines were analyzed in PM 2.5 at Seoul, South Korea.. • Ambient nitramine concentrations were reported for the first time. • Atmospheric reactions might contribute to their formation.. [ABSTRACT FROM AUTHOR]

In this study, the morphological and elemental properties of airborne fine particles (PM 2.5) collected during winter (15 December 2020–14 January 2021) in Ulaanbaatar, Mongolia, were investigated using scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectrometry (EDS). SEM analysis of the PM 2.5 samples revealed that the particle shape distribution on haze days (daily mean PM 2.5 concentration of over 100 μg m−3) was irregular (62%), spherical (24.6%), cluster (10.7%), and chain-like (2.7%), while the particle shape on clean days (daily mean PM 2.5 concentration of less than 30 μg m−3) was distributed as follows: irregular (56%), cluster (22%), spherical (17.3%), and chain-like (4.7%). The apparent mean particle size on haze days (2.07 μm) was twofold greater than that on clean days (1.13 μm). Based on the EDS spectra, carbonaceous particles were the most abundant (38%), followed by mineral dust (36%), Fe-rich particles (4.7%), N-rich particles (4.7%), calcium sulfate (4%), fly ash (4%) and others (2%) on clean days. On haze days, carbonaceous particles accounted for 86% of the total, and Fe-rich, mineral, transition metal, and calcium sulfate particles accounted for 6.7, 4.7, 1.3 and 0.7%, respectively, indicating that carbonaceous particles were the main contributor on haze days. In particular, the sample filters collected on haze days were predominantly covered with tar/soot-like sticky matter, in contrast to those collected on clean days. Spearman's rank correlation analysis of PM 2.5 with inorganic gaseous components as well as meteorological conditions further revealed that high levels of PM 2.5 in winter in Ulaanbaatar were significantly associated with SO 2 (ρ = 0.95), and CO (ρ = 0.94). These associations indicated that ambient SO 2 and CO gases are indicative of haze episodes during the study period, and suggested a strong contribution of solid fuel combustion producing those gases in Ulaanbaatar during winter. [Display omitted] • Morphological and elemental properties of PM 2.5 in Ulaanbaatar was investigated. • Tar/soot-like sticky matter was abundantly observed on the sample filters of haze days. • Apparent mean particle size on haze days was twofold greater than that on clean days. • Ambient SO 2 and CO gases are indicative of haze episodes in Ulaanbaatar during winter. [ABSTRACT FROM AUTHOR]

Northeast Asian countries have suffered from high concentration of the particulate matter (PM 2.5). However, the lack of simultaneous real-time measurements on the PM 2.5 physicochemical characteristics in the different Northeast Asian countries has retarded to understand and mitigate high PM 2.5 air pollution in the continent. In this study, two simultaneous monitoring campaigns were conducted at five supersites in Northeast Asia by deploying same methods using real-time instruments during the winter and summer 2020–2021. Through the campaigns, several high PM 2.5 events were observed in the same periods in the winter among some countries, which were related to the weather conditions. However, the formation and growth trends of PM 2.5 were largely different among the countries, affecting on the spatiotemporal differences of PM 2.5 physicochemical characteristics with local emission. PM 2.5 mass concentration (C PM2.5) measured in Ulaanbaatar (Mongolia) in the winter showed the highest value due to primary emission by fuel-combustion, but lowest in the summer. In contrast, C PM2.5 in Noto (Japan) was lowest during the two campaigns among the countries as a background measurement site. Compared to Seosan and Seoul (Republic of Korea), Beijing (China) showed lower total number of PM 2.5 particles during the winter campaign. However, the PM 2.5 particles were grown larger in Beijing than the two Korean sites, resulting similar average C PM2.5 with the Korean sites in the winter. During the C PM2.5 increased, the real-time concentration of the nitrate increased simultaneously and became the dominant PM 2.5 constituent, which was commonly observed at Seoul, Seosan and Beijing. However, the seasonal changes of the PM 2.5 chemical constituents were different depending on the sites, causing the different seasonal changes of C PM2.5. Otherwise, sulfate and organics significantly contributed to the C PM2.5 (>80%) at Noto, where the C PM2.5 was generally <35 μg/m3 with little amount of nitrate. • FRIEND project conducted simultaneous real-time measurements in Northeast Asia. • Same methods used during the campaigns enabled direct spatiotemporal comparison. • Real-time particle formation and growth were largely different among the countries. • Local emission and formation also affected on PM 2.5 characteristic differences. [ABSTRACT FROM AUTHOR]