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Amines/aminiums are recognized for their importance in new particle formation, organic nitrogen cycle, and aerosol forcings. Among the complex sources, the ocean origins and generation pathways of aminiums are less understood. During a cruise campaign over the Chinese marginal sea (Bohai Sea), five low‐molecular‐weight aminiums were measured. The strong anthropogenic period (terrestrial transport) and the weak anthropogenic period (dust, clean, and sea fog periods) were identified based on the traceable aerosol chemical species, air masses transport patterns, and marine chlorophyll‐a. Inconsistent spatiotemporal variations of various aminiums were observed. Monomethylaminium (MMAH+), dimethylaminium (DMAH+), ethylaminium (EAH+), and diethylaminium (DEAH+) were more enriched during the weak anthropogenic period than the strong anthropogenic period and especially peaked during the sea fog period. The significant correlation between the four aminiums and methanesulfonic acid suggested their secondary formation pathways. Through further exploring the governing factors, the acid–base neutralization via the aqueous phase processing was identified as a critical process for the secondary transformation of aminiums. In contrast, trimethylaminium (TMAH+) showed moderate correlation with Na+ in the total suspended particles only, suggesting its primary marine sources via enrichment in the sea‐spray aerosol through bubble bursting. Based on the step‐wise correlation analysis, the sea surface organic nitrogenous reservoir was found as the dominant contributor to the measured aminiums over the Bohai Sea, while the role of marine phytoplankton emission in the formation of aminiums was limited. Plain Language Summary: Amines have been identified as key species in the formation processes of atmospheric particles, which may further have an impact on climate change. In the marine atmosphere, amines can be emitted from the seawater, while the emission pathway and formation mechanism of different amines are still unclear. It is also ambiguous whether the main contributor of amines over the ocean is dominated by the seawater organic nitrogenous reservoir or the marine phytoplankton emission. In this study, five common particulate aminiums were measured over the Bohai Sea. All aminiums largely originated from ocean during the weak anthropogenic influence period. However, inconsistent spatiotemporal variations and different correlations with some traceable atmospheric chemical components among various aminiums indicated their different emission pathways from the seawater, including seawater bubble bursting and air–sea exchange. For those amines emitted from the latter, the acid–base neutralization in the aqueous phase was identified as a critical process for the emitted gaseous amines to be transformed into their particulate phase. Besides, we found the seawater organic nitrogen reservoir as the dominant contributor to the measured aminiums, overwhelming the influence from the marine phytoplankton emission. Key Points: Atmospheric aminiums were emitted from the ocean through different pathways, that is, sea spray and secondary formationThe acid–base neutralization via the aqueous phase processing was critical for the secondary transformation of aminiumsThe sea surface organic nitrogenous reservoir was found as the dominant contributor to the measured aminiums over the Bohai Sea [ABSTRACT FROM AUTHOR]

Airborne bacteria along with chemical composition of aerosols were investigated during five sampling seasons at an offshore island of the East China Sea. Bacterial diversity was the lowest in spring, the highest in winter, and similar between the autumns of 2019 and 2020, suggesting remarkably seasonal variation but little interannual change. Geodermatophilus (Actinobacteria) was the indicator genus of mineral dust (MD) showed higher proportion in spring than in other seasons. Mastigocladopsis_PCC-10914 (Cyanobacteria) as the indicator of sea salt (SS) demonstrated the highest percentages in both autumns, when the air masses mainly passed over the ocean prior to the sampling site. The higher proportions of soil-derived genera Rubellimicrobium and Craurococcus (both Proteobacteria) and extremophile Chroococcidiopsis_SAG_2023 (Cyanobacteria) were found in summer and winter, respectively. Our study explores the linkage between aerosol source and transport path and bacterial composition, which has implication to understanding of land-sea transmission of bacterial taxa. [Display omitted] • Airborne bacterial diversity was the lowest and highest in spring and winter respectively. • Indicator genera were identified for different aerosol sources including mineral dust and sea salt. • Dust transport of dominant bacteria were changed by high anthropogenic pollution in the path. [ABSTRACT FROM AUTHOR]

An integrated observation of aerosol aminiums was conducted in a coastal city (Shanghai) in eastern China, a nearby island (Huaniao Island), and over the Yellow Sea and East China Sea (YECS). Triethylaminium (TEAH +) was abundant over Shanghai but not detected over the island and the open seas, suggesting its predominantly terrestrial origin. By contrast, relatively high concentrations of dimethylaminium (DMAH +) and trimethylaminium + diethylaminium (TMDEAH +) were measured over the ocean sites, indicating the significant marine source contribution. Environmental factors, including boundary layer height (BLH), temperature, atmospheric oxidizing capacity and relative humidity, were found to be related to aminium concentrations. All the detected aminiums demonstrated the highest levels in winter in Shanghai, consistent with the lowest BLH and temperature in this season. Aminiums mainly existed in fine particles and showed a bimodal distribution, with two peaks at 0.18–0.32 µ m and 0.56–1.0 µ m, indicating that condensation and cloud processing were the main formation pathways for aminiums in analogy with NH4+ and non-sea-salt SO42- (nss-SO 42-). Nonetheless, a unimodal distribution for aerosol aminiums was usually measured over the YECS or over Huaniao Island when influenced mainly by the marine air mass, which suggested that aminiums in marine aerosols may undergo different formation pathways from those on the land. Terrestrial anthropogenic sources and marine biogenic sources were both important contributors for DMAH + and TMDEAH + , and the latter exhibited a significantly higher TMDEAH + to DMAH + ratio. By using the mass ratio of methanesulfonate (MSA) to nss- SO42- as an indicator of marine biogenic source, we estimated that marine biogenic source contributed to 26 %–31 % and 53 %–78 % of aerosol aminiums over Huaniao Island in the autumn of 2016 and summer of 2017, respectively. Due to the important role of atmospheric amines in new particle formation, the estimation results highlighted the importance of marine biogenic emission of amines on the eastern coast of China, especially in summer. [ABSTRACT FROM AUTHOR]

Atmospheric input is an important exogenous source of Fe and Cu to the surface ocean. Here, we investigated temporal and spatial variations, solubilities, size distributions and deposition fluxes of aerosol Fe and Cu using a unique, new dataset including 3-year observations at Huaniao Island and two cruises during the springtimes of 2015 in the Northwest Pacific (NWP) and of 2017 in the Yellow and East China Seas (YECS). The mean concentrations of soluble aerosol Fe and Cu showed a seasonal variation over Huaniao Island with the highest and lowest values in winter and summer respectively, whilst the total Fe reached the maximum in spring. Their mean concentrations decreased significantly from the coastal island to the YECS and to the NWP. The solubility of aerosol Fe was inversely and positively correlated with crustal element Al and non-sea-salt-SO 4 2- (nss-SO 4 2-), respectively. Moreover, the size distribution of soluble Fe demonstrated major peaks in accord with nss-SO 4 2- and a minor peak associated with total Fe. Based on the size distributions of total and soluble Fe, anthropogenic contribution and acid-enhanced dissolution were firstly estimated to be 61% and 32% of soluble Fe over Huaniao Island, 55% and 30% over the YECS, and 34% and 47% over the NWP, respectively. Unlike the Fe, the solubility of aerosol Cu was more correlated with relative humidity (RH). Our estimates of dry deposition fluxes of soluble Fe and Cu declined greatly from the coastal island 33.3 and 2.9 μg m−2 d−1 to the open Pacific 3.6 and 0.1 μg m−2 d−1, respectively. The fluxes of soluble Fe and Cu could vary asynchronously as a result of different origins and transport paths of air masses. Our concurrent study on aerosol Fe and Cu is very helpful for understanding the atmospheric deposition of bioavailable Fe and Cu to the ocean and their interactive effect on marine phytoplankton. • Three-year island and two cruise observations of aerosol Fe and Cu over the NWP and its marginal seas. • Soluble aerosol Fe was correlated with Al and nss-SO 4 2- whereas Cu solubility was correlated with relative humidity. • Soluble Fe and the solubility of Fe decreased and increased from the marginal seas to the NWP, respectively. • A pollution event led to the highest dry fluxes of soluble Fe and Cu while a dust event brought the maximal total Fe. [ABSTRACT FROM AUTHOR]