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Oxygen isotope anomaly of nitrate aerosol (∆17O-NO3−) contributes to understanding the atmospheric nitrogen chemistry in the polar oceans. Here, ∆17O-NO3− of the aerosol samples was analyzed based on a cruise from East Asia to the Arctic Ocean to explore the nitrate formation mechanisms. ∆17O-NO3− decreased with the increase of latitude, especially when after entering the Arctic Circle. ∆17O-NO3− (e.g., 11.5‰–21.2‰) was extremely low while crossing the sea ice-covered Arctic Ocean. This is most likely influenced by the combined enhancement of hydroxyl (OH) and peroxy (HO2 + RO2) radicals derived by sea ice under permanent sunlight period. In addition, the obvious increase in the ∆17O-NO3− of return trip with shortened daytime indicated the advantage of nocturnal pathways (NO3 related) with the higher ∆17O endmembers. The mutation of ∆17O-NO3− can reflect the change of NOx conversion pathways to nitrate, and it can be more sensitive to the change of radical chemistry related to atmospheric oxidation. [ABSTRACT FROM AUTHOR]

To understand the influences of continental emissions on marine aerosols from East Asia, the total suspended particle (TSP) samples were collected from the Yellow Sea (YS) and Bohai Sea (BS) of China through a cruise campaign during the spring of 2018. >100 individual organic compounds were identified and determined in the samples, and they were classified into 6 major groups according to the functionality and sources. The mass concentrations of total quantified organic compounds in BS (307.6 ± 268.3 ng m−3) was approximately 3 times those of YS (111.0 ± 97.3 ng m−3). Organic compounds from biomass burning (23.2 ± 34.2 ng m−3), marine/microbial source (23.1 ± 6.2 ng m−3) and fossil fuel combustion (21.4 ± 11.3 ng m−3) were the most abundant in the YS samples, whereas primary biological origins (90.0 ± 107.1 ng m−3), biomass burning (52.1 ± 39.1 ng m−3) and fossil fuel combustion (41.9 ± 20.1 ng m−3) were the most important organic species in BS marine aerosols. The concentrations of total biogenic secondary organic aerosol (BSOA) tracers including six isoprene SOA (SOA I), three monoterpene SOA (SOA M), and one β -caryophyllene SOA (SOA C) were 2.4 ± 1.5 ng m−3 and 7.3 ± 4.4 ng m−3 in the YS and BS samples, respectively. A strong correlation between BSOA tracers and levoglucosan was shown in the marine aerosol samples, indicating that biomass burning emissions could also promote BSOA formations. The spatial distribution of chemical and source characteristics suggests a relatively large impacts of continental emissions to the BS aerosols. Based on the tracer-based method, the biomass burning (YS: 4.9 ± 6.8%; BS: 8.8 ± 8.0%) was the largest contributor to OC, followed by primary biogenic OC (YS: 0.59 ± 0.44%; BS: 2.9 ± 3.0%) and biogenic secondary OC (YS: 0.45 ± 0.23%; BS: 1.0 ± 0.59%). This study suggests important contributions of biomass burning emissions to organic aerosols in the YS and BS marine atmosphere, although marine source, fossil fuel combustion and secondary formation was also substantial. [Display omitted] • Chemical and source characteristics of marine organic aerosols over the Bohai Sea and Yellow Sea were studied. • Biomass burning is a major contributor of marine organic aerosols over the Bohai Sea and Yellow Sea. • Biogenic primary emission contribution to organic carbon is higher than biogenic-derived secondary formation. • The Bohai Sea is more receptive to the input of continental emissions than the Yellow Sea. [ABSTRACT FROM AUTHOR]

To investigate the characteristics of atmospheric brown carbon (BrC) in the semiarid region of East Asia, PM 2.5 and size-resolved particles in the urban atmosphere of Xi'an, inland China, during the winter and summer of 2017 were collected and analyzed for optical properties and chemical compositions. Methanol extracts (MeOH extracts) were more light-absorbing than water extracts (H2O extracts) in the optical wavelength of 300–600 nm and well correlated with nitrophenols, polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (r>0.78). The light absorptions (abs λ=365nm) of H2O extracts and MeOH extracts in winter were 28±16 and 49±32 M m -1 , respectively, which are about 10 times higher than those in summer, mainly due to the enhanced emissions from biomass burning for house heating. Water-extracted BrC predominately occurred in the fine mode (< 2.1 µ m) during winter and summer, accounting for 81 % and 65 % of the total absorption of BrC, respectively. The light absorption and stable carbon isotope composition measurements showed an increasing ratio of abs λ=365nm -MeOH to abs λ=550nm -EC along with an enrichment of 13C in PM 2.5 during the haze development, indicating an accumulation of secondarily formed BrC (e.g., nitrophenols) in the aerosol aging process. Positive matrix factorization (PMF) analysis showed that biomass burning, fossil fuel combustion, secondary formation, and fugitive dust are the major sources of BrC in the city, accounting for 55 %, 19 %, 16 %, and 10 % of the total BrC of PM 2.5 , respectively. [ABSTRACT FROM AUTHOR]