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[Display omitted] Aerosol ammonium (NH 4 +), mainly produced from the reactions of ammonia (NH 3) with acids in the atmosphere, has significant impacts on air pollution, radiative forcing, and human health. Understanding the source and formation mechanism of NH 4 + can provide scientific insights into air quality improvements. However, the sources of NH 3 in urban areas are not well understood, and few studies focus on NH 3 /NH 4 + at different heights within the atmospheric boundary layer, which hinders a comprehensive understanding of aerosol NH 4 +. In this study, we perform both field observation and modeling studies (the Community Multiscale Air Quality, CMAQ) to investigate regional NH 3 emission sources and vertically resolved NH 4 + formation mechanisms during the winter in Beijing. Both stable nitrogen isotope analyses and CMAQ model suggest that combustion-related NH 3 emissions, including fossil fuel sources, NH 3 slip, and biomass burning, are important sources of aerosol NH 4 + with more than 60% contribution occurring on heavily polluted days. In contrast, volatilization-related NH 3 sources (livestock breeding, N-fertilizer application, and human waste) are dominant on clean days. Combustion-related NH 3 is mostly local from Beijing, and biomass burning is likely an important NH 3 source (∼15%–20%) that was previously overlooked. More effective control strategies such as the two-product (e.g., reducing both SO 2 and NH 3) control policy should be considered to improve air quality. [ABSTRACT FROM AUTHOR]

Objective: To investigate 38 Y-chromosome short tandem repeat (Y-STR) genetic polymorphisms in Beijing Han and analyze the genetic distance with neighboring or linguistically similar populations. Materials and Methods: In the study, we selected 531 unrelated male individuals of Beijing Han, and the results were statistically analyzed by testing with GSTAR™ 41Y reagents. Results: The allele peak heights were balanced among the Y loci, the amplified fragment ranged from 100 to 500 bps. A total of 531 haplotypes were detected in 531 samples. Eight null genotypes were observed on locus DYS448. One and three double alleles were observed on single-copy locus DYS576 and DYS19, respectively. DYS385 a/b, DYF387S1 a/b, and DYS527 a/b were more common in double copies, but 3, 13, and 11 triple alleles were detected, respectively. The gene diversity values of Y-STRs except DYS391, DYS438, and DYS645 were >0.5. Twenty-seven Y-STRs of Beijing Han population were selected for genetic distance comparison with 17 populations including Changchun Han, with Rst values ranging from 0.0002 to 0.1703. Conclusion: The 38 Y-STRs in this study have strong male lineage identification ability and have great potential for individual identification, kinship identification, Y-STR database construction, and genetic relationship research. [ABSTRACT FROM AUTHOR]

Secondary organic aerosol (SOA) plays a significant role in atmospheric chemistry. However, little is known about the vertical profiles of SOA in the urban boundary layer (UBL). This knowledge gap constrains the SOA simulation in chemical transport models. Here, the aerosol samples were synchronously collected at 8, 120, and 260 m based on a 325 m meteorological tower in Beijing from 15 August to 10 September 2015. Strict emission controls were implemented during this period for the 2015 China Victory Day parade. Here, we observed that the total concentration of biogenic SOA tracers increased with height. The fraction of SOA from isoprene oxidation increased with height, whereas the fractions of SOA from monoterpenes and sesquiterpenes decreased, and 2,3-dihydroxy-4-oxopentanoic acid (DHOPA), a tracer of anthropogenic SOA from toluene oxidation, also increased with height. The complicated vertical profiles of SOA tracers highlighted the need to characterize SOA within the UBL. The mass concentration of estimated secondary organic carbon (SOC) ranged from 341 to 673 ngCm-3. The increase in the estimated SOC fractions from isoprene and toluene with height was found to be more related to regional transport, whereas the decrease in the estimated SOC from monoterpenes and sesquiterpene with height was more subject to local emissions. Emission controls during the parade reduced SOC by 4 %–35 %, with toluene SOC decreasing more than the other SOC. This study demonstrates that vertical distributions of SOA within the UBL are complex, and the vertical profiles of SOA concentrations and sources should be considered in field and modeling studies in the future. [ABSTRACT FROM AUTHOR]

Biomass burning and primary biological aerosol particles account for an important part of urban aerosols. Floods of studies have been conducted on the chemical compositions of fine aerosols (PM 2.5) in megacities where the haze pollution is one of the severe environmental issues in China. However, little is known about their size distributions in atmospheric aerosols in the urban boundary layer. Here, size-segregated aerosol samples were collected in Beijing during haze and clear days from April 2017 to January 2018. Three anhydrosugars, six primary saccharides and four sugar alcohols in these samples were identified and quantified by gas chromatography/mass spectrometry (GC/MS). Higher concentrations of a biomass burning tracer, levoglucosan, were detected in autumn and winter than in other seasons. Sucrose, glucose, fructose, mannitol and arabitol were more abundant in the bloom and glowing seasons. A particularly high level of trehalose was found in spring, which was largely associated with the Asian dust outflows. Anhydrosugars, xylose, maltose, inositol and erythritol are mainly present in the fine mode (<2.1 µ m), while the others showed the coarse-mode preference. The concentrations of measured tracers of biomass burning particles and primary biological particles in the haze events were higher than those in the non-hazy days, with enrichment factors of 2–10. Geometric mean diameters (GMDs) of molecular markers of biomass burning and primary biological aerosols showed that there was no significant difference in the coarse mode (>2.1 µ m) between the haze and non-haze samples, while a size shift towards large particles and large GMDs in the fine fraction (<2.1 µ m) was detected during the hazy days, which highlights that the stable meteorological conditions with high relative humidity in urban Beijing may favor the condensation of organics onto coarse particles.The contributions of reconstructed primary organic carbon (POC) by tracer-based methods from plant debris, fungal spores and biomass burning to aerosol OC in the total-mode particles were in the ranges of 0.09 %–0.30 % (on average 0.21 %), 0.13 %–1.0 % (0.38 %) and 1.2 %–7.5 % (4.5 %), respectively. This study demonstrates that the contribution of biomass burning was significant in Beijing throughout the whole year with the predominance in the fine mode, while the contributions of plant debris and fungal spores dominated in spring and summer in the coarse mode, especially in sizes >5.8 µ m. Our observations demonstrate that the sources, abundance and chemical composition of urban aerosol particles are strongly size dependent in Beijing, which is important to better understand the environmental and health effects of urban aerosols and should be considered in air quality and climate models. [ABSTRACT FROM AUTHOR]

Low molecular weight organic compounds are ubiquitous in the atmosphere. However, knowledge on their concentrations and molecular distribution in fresh snow remains limited. Here, twelve fresh snow samples collected at eight sites in China were investigated for dicarboxylic acids and related compounds (DCRCs) including oxocarboxylic acids and α-dicarbonyls. Dissolved organic carbon (DOC) concentrations in the snow samples ranged from 0.99 to 14.6 mg C L−1. Concentrations of total dicarboxylic acids were from 225 to 1970 μg L−1 (av. 650 μg L−1), while oxoacids (28.3–173, av. 68.1 μg L−1) and dicarbonyls (12.6–69.2, av. 31.3 μg L−1) were less abundant, accounting for 4.6–8.5% (6.2%), 0.45–1.4% (0.73%), and 0.12–0.88% (0.46%) of DOC, respectively. Molecular patterns of dicarboxylic acids are characterized by a predominance of oxalic acid (C 2) (95.0–1030, av. 310 μg L−1), followed by phthalic (Ph) (9.69–244, av. 69.9 μg L−1) or succinic (C 4) (23.8–163, av. 63.7 μg L−1) acid. Higher concentrations of Ph in snow from Beijing and Tianjin than other urban and rural regions suggest significant emissions from vehicular exhausts and other fossil fuel combustion sources in megacities. C 2 constituted 40–54% of total diacids, corresponding to 1.5–2.6% of snow DOC. The total measured DCRCs represent 5.5–10% of snow DOC, which suggests that there are large amounts of unknown organics requiring further investigations. The spatial distributions of diacids exhibited higher loadings in megacities than rural and island sites. Molecular distributions of diacids indicated that the photochemical modification was restrained under the weak solar radiation during the snow events, while anthropogenic primary sources had a more significant influence in megacities than rural areas and islands. • Dicarboxylic acids and related compounds were analyzed in urban, rural and island snow samples. • Total measured dicarboxylic acids and related compounds represent 5.5–10% of snow DOC. • High abundance of phthalic acid in urban snow suggests strong emission from fossil fuel combustion. [ABSTRACT FROM AUTHOR]