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Severe haze in Beijing is characterized by the rapid formation of sulfate via the multiphase oxidation of SO2. While many factors, including aerosol oxidants and atmospheric variables, were discovered and investigated, their relative importance remains unclear. Herein, based on the field observation data obtained in Beijing, China, we developed a kinetic model to explore the key factors that determine the multiphase formation of sulfate. Sensitivity tests give the kinetics of each oxidation pathway varying with pH and temperature, based on which the total sulfate formation rate at room temperature (298 K) is calculated to be generally greater than that at standard temperature (273 K), especially during nighttime. Interfacial oxidants are responsible for sulfate formation within a wide pH range, and transition metal ions become more efficient with increased temperature. The multiphase chemistry is additionally affected by aerosol liquid water content (ALWC), particle radius (Rp), and ionic strength (IS). Within the usual aerosol acidity, the kinetic discrepancy induced by different ALWC levels is more significant at the lower temperature, in contrast to the temperature dependence related to Rp, and the effect of IS depends highly on pH. Machine learning reveals the potential importance of temperature, acidity, and Rp. Temperature and acidity are impactful for the formation of both aqueous and interfacial sulfates, whereas Rp only affects the interfacial processes. The discrepancy between nighttime and daytime is considered throughout this study. Overall, this study reveals the key factors for multiphase sulfate formation and is recommended for kinetic evaluation in future laboratory research. Plain Language Summary: Sulfate is an important constituent in the atmospheric aerosol community because it facilitates haze formation and affects public health. In the past years, scientists reproduced the multiphase oxidation of sulfur dioxide in the laboratory, as an attempt to explain the secondary sulfate burst. However, we should note that the sulfate formation rate calculated by the parameters derived from the experiments performed under room temperature (∼298 K) was normally compared with the kinetics estimated under standard temperature (∼273 K). Furthermore, other atmospheric variables besides temperature, including aerosol liquid water content, particle radius, and ionic strength, were normally set as constant rather than adjusted by experimental conditions. To solve the uncertainties, we developed a kinetic model by incorporating the documented multiphase sulfate formation pathways. Based on this model, researchers can evaluate the previously documented or newly discovered sulfate formation pathways in a more reasonable way. The developed kinetic model, and its improved versions in the following, are recommended for future laboratory works to reveal the key factors, including aerosol oxidants and atmospheric variables, that determine the multiphase formation of sulfate aerosols. Key Points: This work develops a kinetic model to reveal the key factors determining the multiphase formation of sulfate under Beijing conditionsResults emphasize the importance of transition metal ions, serving as both aqueous and interfacial catalystsTemperature, acidity, and particle radius could be key variables influencing the multiphase sulfate formation [ABSTRACT FROM AUTHOR]

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]

Methanesulfonate (MSA) in the marine boundary layer is commonly considered to be solely contributed by the oxidation of ocean‐derived dimethyl sulfide (DMS) and often used as an indicator of marine biogenic sources. But whether this judgment is valid in coastal seas and how the validity is affected by air mass transport history have been less discussed. Based on multi‐year observations of aerosol MSA in the coastal East China Sea (ECS) and the Gulf of Aqaba (GA), as well as the analysis of air mass transport pattern and exposure to ocean surface phytoplankton biomass, we found that terrestrial sources made a non‐negligible contribution to MSA over the ECS but not over the GA. The abundant MSA in winter over the coastal ECS was likely associated with substantial emissions of volatile organic sulfur compounds from both anthropogenic and natural sources in eastern China and significant terrestrial transport influenced by the East Asian Monsoon. Good correlations between aerosol MSA and air mass exposure to surface phytoplankton biomass were established by removing the influence of terrestrial transport and confining the air transport height within boundary layer, which makes it possible to construct parameterizations for obtaining the spatiotemporal distributions of marine biogenic aerosol components using satellite ocean color datasets. Key Points: The concentrations of aerosol methanesulfonate over coastal East China Sea and the Gulf of Aqaba exhibit distinct seasonal variationsTerrestrial sources make a substantial contribution to methanesulfonate in autumn and winter over coastal East China SeaAir transport height greatly affects the linkage between aerosol methanesulfonate and phytoplankton biomass [ABSTRACT FROM AUTHOR]

Haptophytes and Dinoflagellates are two cosmopolitan algae associated with dimethylsulfoniopropionate (DMSP) synthesis, which regulates the marine biogenic flux of DMS to the atmosphere with potential effects on global climate. Attempting to reveal the potential impact of atmospheric deposition on the growth of high‐DMSP producers, four bioassay experiments were conducted in the western North Pacific (WNP) by adding aerosols, nutrients, and trace metals. Our results showed that the percentage of high‐DMSP producers increased substantially from coastal seas (<1%) to the open ocean (∼17%) with the dominance of Dinophyceae and Haptophyceae, respectively. Aerosol additions largely increased the percentage of high‐DMSP producing species in the subtropical gyre of WNP. Specifically, atmospheric dissolved inorganic nitrogen, soluble Cu and Fe promoted Dinophyceae taxa, Chrysochromulina, and Phaeocystis and E. huxleyi, respectively. It is very likely that atmospheric deposition could lift the relative abundance of high‐DMSP producers in the vast oligotrophic oceans and potentially contribute to the climate change. Plain Language Summary: Dimethylsulfoniopropionate (DMSP) is an important precursor of dimethyl sulfide (DMS) and metabolite of algae, which may alter the radiative balance and regulate the global climate. We have conducted four bioassay experiments in different regions of the WNP, simulating atmospheric inputs of nutrients and trace metals analogue to their contents in aerosols. The proportion of high‐DMSP producers increased substantially with the distance offshore, and the dominant species transferred from Dinophyceae to Haptophyceae. It was demonstrated that atmospheric deposition could elevate the proportion of high‐DMSP producers in the oligotrophic ocean rather than in coastal seas. Their larger size compared with Cyanobacteria and special mechanism of metal digestion might be the reason. With the intensive human activities and increasing atmospheric deposition, this stimulation effect may be significantly enhanced and the subsequent climate effects are non‐negligible, especially in those oligotrophic regions. Our results may provide new insights into the ecological effects and climate change. Key Points: Dinophyceae and Haptophyceae were the prime high‐dimethylsulfoniopropionate (DMSP) producers in the coastal and oligotrophic oceans, respectivelyAtmospheric deposition could elevate the proportion of high‐DMSP producers in the oligotrophic oceanDissolved inorganic nitrogen and Cu increased the proportion of Chrysochromulina whilst Fe benefited Phaeocystis and E. huxleyi [ABSTRACT FROM AUTHOR]

Biogenic emission of dimethyl sulfide (DMS) from seawater is the major natural source of sulfur into the atmosphere. In this study, we use an advanced air quality model (CMAQv5.2) with DMS chemistry to examine the impact of DMS emissions from seawater on summertime air quality over China. A national scale database of DMS concentration in seawater is established based on a 5‐year observational record in the East China seas including the Bohai Sea, the Yellow Sea, and the East China Sea. We employ a commonly used global database and also the newly developed local database of oceanic DMS concentration, calculate DMS emissions using three different parameterization schemes, and perform five different model simulations for July, 2018. Results indicate that in large coastal areas of China, the average DMS emissions flux obtained with the local database is 3 times higher than that resulting from the global database, with a mean value of 9.1 μmol m−2 day−1 in the Bohai Sea, 8.4 μmol m−2 day−1 in the Yellow Sea, and 13.4 μmol m−2 day−1 in the East China Sea. The total DMS emissions flux calculated with the Nightingale scheme is 42% higher than that obtained with the Liss and Merlivat scheme but is 15% lower than that obtained with the Wanninkhof scheme. Among the three parameterizations, results of the Liss and Merlivat scheme agree better with the ship‐based observations over China's coastal waters. DMS emissions with the Liss and Merlivat parametrization increase atmospheric sulfur dioxide (SO2) and sulfate (SO42−) concentration over the East China seas by 6.4% and 3.3%, respectively. Our results indicate that although the anthropogenic source is still the dominant contributor of atmospheric sulfur burden in China, biogenic DMS emissions source is nonnegligible. Key Points: The use of local database better reproduces DMS emission fluxes over China's seawaterThe LM86 parameterization (Liss & Merlivat, 1986, https://doi.org/10.1007/978‐94‐009‐4738‐2%5f5) produces the best performance among the three tested schemes in China's offshore watersThe marine DMS emissions increase SO2 and SO42‐ in the atmosphere of the eastern China Sea [ABSTRACT FROM AUTHOR]