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New particle formation (NPF) is one of the major contributors to atmospheric aerosol number concentrations. The initial step of NPF includes the formation and growth of small clusters, their evaporation and loss to pre-existing particles (characterized by the condensation sink, CS). In the polluted atmospheric boundary layer, the high environmental CS suppresses NPF and it can work synergistically with evaporation to further reduce the NPF rates. In this study, to quantitatively include CS into NPF analysis, we make simplifications to the cluster balance equations and develop approximate equations for the NPF rates in the presence of pre-existing particles, which are applicable to nucleation mechanisms that can be represented by a nonbranched nucleation pathway. The developed equations show that the proportion of clusters that finally lead to new particle formation is given by the cluster-specific ratio of growth rate/CS | evaporation rate | growth rate. As a result, the cumulative product of this ratio for all clusters in the nucleation pathway determines the NPF rates. By comparing with benchmark cluster dynamics simulations of sulfuric acid-dimethylamine and sulfuric acid-ammonia nucleation systems, the developed equations were confirmed to give good estimates of the NPF rates and approximately capture the dependency of NPF rates on CS and nucleating vapor concentrations. The CS dependency predicted by the developed equations shows larger deviations from the simulations when the cluster evaporation rates are high, i.e., when the underlying assumptions of the equations are not satisfied. The equations were also found to be in good agreement with atmospheric NPF rates measured in long-term field observations in urban Beijing.

Carbon dioxide is considered an inert gas that rarely participates in atmospheric chemical reactions. Nonetheless, we show here that CO2 is involved in some important photo-oxidation reactions in the atmosphere through the formation of carbonate radicals (CO3⚫-). This potentially active intermediate CO3⚫- is routinely overlooked in atmospheric chemistry concerning its effect on sulfate formation. The present work demonstrates that the SO2 uptake coefficient is enhanced by 17 times on mineral dust particles driven by CO3⚫-. Importantly, upon irradiation, mineral dust particles are speculated to produce gas-phase carbonate radical ions when the atmospherically relevant concentration of CO2 presents, thereby potentially promoting external sulfate aerosol formation and oxidative potential in the atmosphere. Employing a suite of laboratory investigations of sulfate formation in the presence of carbonate radicals on the model and authentic dust particles, ground-based field measurements of sulfate and (bi)carbonate ions within ambient PM, together with density functional theory (DFT) calculations for single electron transfer processes in terms of CO3⚫--initiated S(IV) oxidation, a novel role of carbonate radical in atmospheric chemistry is elucidated.

Both iodic acid (HIO3, IA) and methanesulfonic acid (CH3S(O)2OH, MSA) have been identified by field studies as important precursors of new particle formation (NPF) in marine areas. However, the mechanism of NPF in which IA and MSA are jointly involved is still unclear. Hence, we investigated the IA-MSA nucleation system under different atmospheric conditions and uncovered the corresponding nucleating mechanism at the molecular level for the first time, using a quantum chemical approach and Atmospheric Cluster Dynamics Code (ACDC). The findings show that the pure-IA nucleation rate was much lower than the results of CLOUD (Cosmics Leaving Outdoor Droplets) experiments. MSA can promote IA cluster formation through stabilizing IA via both hydrogen and halogen bonds, especially under conditions with lower temperatures, sparse IA, and rich MSA. However, the nucleation rate of the IA-MSA mechanism is much lower than that of field observations, indicating that the effect of additional nucleation precursors needs to be considered (e.g., H2SO4, HIO2, NH3, and amines). The IA-MSA nucleation mechanism revealed in this study may help to gain insight into the joint effect of marine sulfur- and iodine-containing components on marine NPF.

Aerosol microdroplets as microreactors for many important atmospheric reactions are ubiquitous in the atmosphere. pH largely regulates the chemical processes within them; however, how pH and chemical species spatially distribute within an atmospheric microdroplet is still under intense debate. The challenge is to measure pH distribution within a tiny volume without affecting the chemical species distribution. We demonstrate a method based on stimulated Raman scattering microscopy to visualize the three-dimensional pH distribution inside single microdroplets of varying sizes. We find that the surface of all microdroplets is more acidic, and a monotonic trend of pH decreasing is observed in the 2.9-μm aerosol microdroplet from center to edge, which is well supported by molecular dynamics simulation. However, bigger cloud microdroplet differs from small aerosol for pH distribution. This size-dependent pH distribution in microdroplets can be related to the surface-to-volume ratio. This work presents noncontact measurement and chemical imaging of pH distribution in microdroplets, filling the gap in our understanding of spatial pH in atmospheric aerosol.

The role of pyruvic acid (PA), one of the most abundant α-keto carboxylic acids in the atmosphere, was investigated both in the SO3 hydrolysis reaction to form sulfuric acid (SA) and in SA-based aerosol particle formation using quantum chemical calculations and a cluster dynamics model. We found that the PA-catalyzed SO3 hydrolysis is a thermodynamically driven transformation process, proceeding with a negative Gibbs free-energy barrier, ca. −1 kcal mol−1 at 298 K, ∼ 6.50 kcal mol−1 lower than that in the water-catalyzed SO3 hydrolysis. Results indicated that the PA-catalyzed reaction can potentially compete with the water-catalyzed SO3 reaction in SA production, especially in dry and polluted areas, where it is found to be ∼ 2 orders of magnitude more efficient that the water-catalyzed reaction. Given the effective stabilization of the PA-catalyzed SO3 hydrolysis product as SA⚫PA cluster, we proceeded to examine the PA clustering efficiency in a sulfuric-acid–pyruvic-acid–ammonia (SA-PA-NH3) system. Our thermodynamic data used in the Atmospheric Cluster Dynamics Code indicated that under relevant tropospheric temperatures and concentrations of SA (106 molec.cm-3), PA (1010 molec.cm-3) and NH3 (1011 and 5 × 1011 molec.cm-3), PA-enhanced particle formation involves clusters containing at most one PA molecule. Namely, under these monomer concentrations and 238 K, the (SA)2⚫PA⚫(NH3)2 cluster was found to contribute by ∼ 100 % to the net flux to aerosol particle formation. At higher temperatures (258 and 278 K), however, the net flux to the particle formation is dominated by pure SA-NH3 clusters, while PA would rather evaporate from the clusters at high temperatures and not contribute to the particle formation. The enhancing effect of PA was examined by evaluating the ratio of the ternary SA-PA-NH3 cluster formation rate to binary SA-NH3 cluster formation rate. Our results show that while the enhancement factor of PA to the particle formation rate is almost insensitive to investigated temperatures and concentrations, it can be as high as 4.7 × 102 at 238 K and [NH3] = 1.3 × 1011 molec.cm-3. This indicates that PA may actively participate in aerosol formation, only in cold regions of the troposphere and highly NH3-polluted environments. The inclusion of this mechanism in aerosol models may reduce uncertainties that prevail in modeling the aerosol impact on climate.

In comparison with iodic acid, iodous acid is a potentially important nucleation precursor in marine regions.

A cheap and easily available ZnEt2 is an effective precatalyst, which can be used for the hydroboration reaction of various organic carbonates and esters with HBpin.

By seeding clouds, new particle formation (NPF) has a substantial impact on radiation balance, bio-geochemical cycles and global climate. Over oceans, both methanesulfonic acid (CH3S(O)2OH, MSA) and iodous acid (HIO2)...

Tetranuclear Cp4M4(CO)4 clusters have been synthesized for iron and vanadium but not for the intermediate first-row transition metals manganese and chromium. All of the low-energy structures of these "missing" Cp4M4(CO)4 (M = Mn, Cr) species are shown by density functional theory to consist of a central M4 tetrahedron with each of the four faces capped by a μ3-CO group. The individual low-energy structures differ in their spin states and in their formal metal-metal bond orders along the six edges of their central M4 tetrahedra. The two low-energy Cp4Mn4(μ3-CO)4 structures are a triplet structure with all Mn-Mn single bonds and a singlet structure with one Mn≡Mn triple bond and five Mn-Mn single bonds along the six tetrahedral edges. Related low-energy Cp4Cr4(μ3-CO)4 structures include a quintet structure with all Cr-Cr single bonds and a singlet structure with two Cr≡Cr triple bonds and four Cr-Cr single bonds. However, the potential energy surface of the Cp4Cr4(CO)4 system is complicated by three other structures of comparable energies including two triplet structures and one quintet structure with various combinations of single, double, and triple chromium-chromium bonds in the central Cr4 tetrahedron.

Forming an (H2SO4)(1)(amine)(1) cluster is the rate-limiting step in atmospheric H2SO4-amine nucleation, which governs the fast formation of new particles from gaseous precursors.Transformation of low-volatility gaseous precursors to new particles affects aerosol number concentration, cloud formation and hence the climate. The clustering of acid and base molecules is a major mechanism driving fast nucleation and initial growth of new particles in the atmosphere. However, the acid-base cluster composition, measured using state-of-the-art mass spectrometers, cannot explain the measured high formation rate of new particles. Here we present strong evidence for the existence of base molecules such as amines in the smallest atmospheric sulfuric acid clusters prior to their detection by mass spectrometers. We demonstrate that forming (H2SO4)(1)(amine)(1) is the rate-limiting step in atmospheric H2SO4-amine nucleation and the uptake of (H2SO4)(1)(amine)(1) is a major pathway for the initial growth of H2SO4 clusters. The proposed mechanism is very consistent with measured new particle formation in urban Beijing, in which dimethylamine is the key base for H2SO4 nucleation while other bases such as ammonia may contribute to the growth of larger clusters. Our findings further underline the fact that strong amines, even at low concentrations and when undetected in the smallest clusters, can be crucial to particle formation in the planetary boundary layer.

Carbon capture and storage (CCS) is an effective means of mitigating anthropogenic CO2 emissions in the atmosphere. However, it is important to consider the risks of CO2 leakage from storage sites and their potential impacts on near-surface ecosystems. We explored the impact of increased soil CO2 concentrations on sunflowers (Helianthus annuus Linn.), a main oil crop, using pot experiments. The results indicate that the crude fat content of the sunflowers decreased by 3.62%, whereas the crude protein content and linoleic acid contents increased by 4.12% and 13.98%, respectively; sunflower yields remain unchanged under 1500 g m−2 day−1 CO2 leakage. We confirmed that the sunflower oil content decreased because of higher soil CO2. A decrease in sunflower oil production rates will reduce their commercial value. The elevated crude protein and linoleic acid contents increased the nutrients in sunflower meal and edible oil, indicating that increased CO2 in soil caused by CCS leakage can improve the quality of sunflower oil to some extent. Considering the tolerance of sunflowers to CO2 leakage, planting sunflowers in CCS project areas is a feasible solution for addressing CO2 leakage.

Recent research has shown the almost barrierless cycloaddition reaction of the carboxylic acid with one SO3 to form products with group of -OSO3H, which can form stable clusters with the nucleation precursors through hydrogen bonds (Mackenzie et al., Science 2015, 349, 58). Oxalic acid (OA), the simplest and prevalent dicarboxylic acid, was selected as an example to clarify the possibility to react with two SO3 sequentially and the nucleation potential of products. The results indicate that OA can sequentially react with two SO3 through low reaction barriers to form the primary product (oxalic sulfuric anhydride (OSA)) and the secondary product (oxalic disulfuric anhydride (ODSA)). Interactions between atmospheric nucleation precursors and OSA, ODSA, or OA are in the order of ODSA > OSA > OA through evaluating the stability of generated clusters by the topological, thermodynamics, and kinetic analysis, which implies generated products could be nucleation stabilizers with nucleation potential positively correlating with the number of -OSO3H. This reaction mechanism contributes to a comprehensive understanding of the reactivity of dicarboxylic acid in the polluted environment as well as the role of products in organosulfur chemistry and, to some extent, help to explain the missing sources of new particle formation.

Iodous acid (HIO

Graphite is useful as a low-cost and high-voltage cathode of dual-ion batteries (DIBs) to allow anion (de-)intercalation, yet its practical applications are hindered by low Coulombic efficiencies (...

Comprehensive investigations of the possible formation pathways of sulfate, the main composition of atmospheric aerosol in marine areas, continue to challenge atmospheric chemists. As one of the most important oxidation routes of S(IV) contributing to sulfate formation, the reaction process of S(IV) oxidized by hypobromic acid, which is ubiquitous with the gas-phase mixing ratios of ∼310 ppt and has a well-known oxidative capacity, has attracted wide attention. However, little information is available about the detailed reaction mechanism. Especially, due to the abundant species in cloud water, the potential effect of these compositions on these reaction processes and the corresponding effect mechanism are also uncertain. Using high-level quantum chemical calculations, we theoretically elucidate the two-step mechanism of Br+ transfer proposed by experiment through the verification of the key BrSO3− intermediate formation and subsequent hydrolysis reaction or the uncovered reaction of BrSO3− intermediate with OH−. Further, the novel and more competitive mechanisms (OH+ or O atom transfer pathways) that have not been considered in previous studies, leading to sulfate formation directly, have been found. Furthermore, it should be mentioned that we revealed the effect mechanism of constituents catalyzed in cloud water, especially the important H2O-catalyzed mechanism. In addition, all the above pathways follow this catalytic mechanism. This finding indicates a linkage between the complex nature of the atmospheric constituents and related atmospheric reaction, as well as the enhanced occurrence of atmospheric secondary sulfate formation in the atmosphere. Hence, this exploration of sulfate formation related to hypobromic acid could provide a better understanding about the sources of sulfate in marine areas.

Oxocarboxylic acids, one of the most important organic species, are detected in aerosols in various environments. Recent studies suggest that the gas-phase reactions between carboxylic acids and SO3 could form carboxylic sulfuric anhydrides, which might participate in nucleation. Here, glyoxylic acid (GA), the most abundant oxocarboxylic acid in the atmosphere, has been selected as an example to study the reactions between oxocarboxylic acids and SO3 and the nucleation potentials of products. The reaction between GA and SO3 that generates glyoxylic sulfuric anhydride (GSA) and the hydrolysis of GSA are investigated using computational methods. The results show that the reaction is almost barrierless, and GSA is stable against water. Additionally, the clusters of GSA and common nucleation species (sulfuric acid and ammonia) are more stable than the analogous clusters of GA, because they have more hydrogen bonds and proton transfers. It suggests that GA tends to transfer itself to a much better nucleation precursor, GSA, through a reaction with SO3, and GSA can drive nucleation and contribute to new particle formation (NPF). This mechanism might be general for all oxocarboxylic acids and could help to deeply understand the roles of oxocarboxylic acids in NPF.

Environmentally persistent free radicals (EPFRs) have been recognized as harmful and persistent environmental pollutants. In polluted regions, many acidic and basic atmospheric pollutants, which are present at high concentrations, may influence the extent of the formation of EPFRs. In the present paper, density functional theory (DFT) and ab-initio molecular dynamics (AIMD) calculations were performed to investigate the formation mechanisms of EPFRs with the influence of the acidic pollutants sulfuric acid (SA), nitric acid (NA), organic acid (OA), and the basic pollutants, ammonia (A), dimethylamine (DMA) on α-Al

We report on the study of phonon properties and electron-phonon coupling in thin NbTiN films, which are intensively exploited in superconducting devices. Studied NbTiN films with thicknesses less than 10~nm are disordered with respect to electron transport, the Ioffe-Regel parameter of $k_F l_e = 2.5-3.0$ ($k_F$ is the Fermi wave vector and $l_e$ is the electron mean free path), and inelastic electron-phonon interaction, the product $q_T l_e \ll 1$ ($q_T$ is the wave vector of a thermal phonon). By means of magnetoconductance and photoresponse techniques, we derived the inelastic electron-phonon scattering rate $1/\tau_{e-ph}$ and determined sound velocities and phonon heat capacities. In the temperature range from 12 to 20~K, the scattering rate varies with temperature as $1/\tau_{e-ph}\propto T^{3.45\pm0.05}$; its value extrapolated to 10~K amounts to approximately 16~ps. Making a comparative analysis of our films and other films used in superconducting devices, such as polycrystalline granular NbN and amorphous WSi, we found a systematic reduction of the sound velocity in all these films by about 50\% as compared to the corresponding bulk crystalline materials. A corresponding increase in the phonon heat capacities in all these films is, however, less than the Debye model predicts. We attribute these findings to reduced film dimensionality and film morphology.

The role of pyruvic acid (PA), one of the most abundant α-keto carboxylic acids in the atmosphere, was investigated both in the SO3 hydrolysis reaction to form sulfuric acid (SA) and in SA-based aerosol particle formation using quantum chemical calculations and a cluster dynamics model. We found that the PA-catalyzed SO3 hydrolysis is a thermodynamically driven transformation process, proceeding with a negative Gibbs free energy barrier, ca. −1 kcal mol−1 at 298 K, ~6.50 kcal mol−1 lower than that in the water-catalyzed SO3 hydrolysis. Results indicated that the PA-catalyzed reaction can potentially compete with the water-catalyzed SO3 reaction in SA production, especially in dry and polluted areas, where it is found to be ~two orders of magnitude more efficient that the water-catalyzed reaction. Given the effective stabilization of the PA-catalyzed SO3 hydrolysis product as SA•PA cluster, we proceeded to examine the PA clustering efficiency in sulfuric acid-pyruvic acid-ammonia (SA-PA-NH3) system. Our thermodynamic data used in the Atmospheric Cluster Dynamics Code indicated that under relevant tropospheric temperatures and concentrations of SA (106 cm3), PA (1010 cm3) and NH3 (1011 and 5 × 1011 cm3), of the PA-containing clusters, only clusters with one PA molecule, namely (SA)2•PA•(NH3)2, can participate to the particle formation, contributing by ~100 % to the net flux to aerosol particle formation at 238 K, exclusively. At higher temperatures (258 K and 278 K), however, the net flux to the particle formation is dominated by pure SA-NH3 clusters, while PA would rather evaporate from the clusters at high temperatures and not contribute to the particle formation. The enhancing effect of PA of examined by evaluating the ratio of the ternary SA-PA-NH3 cluster formation rate to binary SA-NH3 cluster formation rate. Our results show that while the enhancement factor of PA to the particle formation rate is almost insensitive to investigated temperatures and concentrations, it can be as high as 4.7 × 102 at 238 K and [NH3] = 1.3 × 1011 molecule cm−3. This indicates that PA may actively participate in aerosol formation, only in cold regions of the troposphere and highly NH3-polluted environments. The inclusion of this mechanism in aerosol models may definitely reduce uncertainties that prevail in modeling the aerosol impact on climate.

Despite the high abundance in the atmosphere, alcohols in general and methanol in particular are believed to play a small role in atmospheric new particle formation (NPF) largely due to the weak binding abilities of alcohols with the major nucleation precursors, e.g., sulfuric acid (SA) and dimethylamine (DMA). Herein, we identify a catalytic reaction that was previously overlooked, namely, the reaction between methanol and SO3, catalyzed by SA, DMA, or water. We found that alcohols can have unexpected quenching effects on the NPF process, particularly in dry and highly polluted regions with high concentrations of alcohols. Specifically, the catalytic reaction between methanol and SO3 can convert methanol into a less-volatile species-methyl hydrogen sulfate (MHS). The latter was initially thought to be a good nucleation agent for NPF. However, our simulation results suggest that the formation of MHS consumes an appreciable amount of atmospheric SO3, disfavoring further reactions of SO3 with H2O. Indeed, we found that MHS formation can cause a reduction of SA concentration up to 87%, whereas the nucleation ability of MHS toward new particles is not as good as that of SA. Hence, a high abundance of methanol in the atmosphere can lower the particle nucleation rate by as much as two orders of magnitude. Such a quenching effect suggests that the recently identified catalytic reactions between alcohols and SO3 need to be considered in atmospheric modeling in order to predict SA concentration from SO2, while also account for their potentially negative effect on NPF.

Starting soon after discovery, we carried out a programme of continuous observations for the active comet C/2017 K2 (PANSTARRS) using the Lijiang 2.4 m telescope from 2017 September 8 to 2018 June 18 with a Johnson R filter. Three fixed linear apertures of ra1 = 6.4 x 104 km, ra2 = 7.7 x 104 km and ra3 = 9.6 x 104 km were chosen to measure the brightness of C/2017 K2 respectively, and the instrumental magnitudes were then converted into the PS1 r system. During the period of observation, the cross-section area increased at rates of 22.0, 28.5 and 44.1 km2 d(-1) relative to the different linear photometry apertures, and the corresponding mass-loss rates were 63.8 kg s(-1), 82.6 kg s(-1) and 127.5 kg s(-1), assuming that the dust-particle size is (a) over bar = 0.5 mm and the density is. = 500 kgm(3). The size of the C/2017 K2 nucleus is estimated as 1.2 less than or similar to rn less than or similar to 2.5 km for CO sublimation and 3.1 less than or similar to rn less than or similar to 183.9 km for CO2 with an aperture of 9.6 x 10(4) km; meanwhile the grain size of K2 is ac less than or similar to 9 mm for CO and a(c) less than or similar to 0.8 mm for CO2. The long-term monitoring data provided in this paper will be very valuable and helpful for studying the activity mechanism of C/2017 K2.

In the working of the existing reference coordinate system transformed into the coordinate system of the geocentric coordinate system, many experts and scholars have in-depth research on the transformation methods such as geodetic control point results (including GNSS base station coordinates, GNSS control point coordinates, triangle point coordinates), basic geographic information data results (including DLG, DOM, DEM, DRG, DSM, etc.) and other spatial information data. On the basis of these studies, many provinces and cities have completed the coordinate system transformation of surveying and mapping results in China. This paper expounds the method of transforming the existing reference coordinate system into the geocentric coordinate system, summarizes and sorts out the common quality problems in the process of different data and different methods, and analyses the causes of the problems and the impact on the transforming results. Based on the above work, The paper provides reference and suggestions for the transforming work, which is aimed to improve the transformation quality in the future.

The gas-phase reaction of organic acids with SO3 has been recognized as essential in promoting aerosol-particle formation. However, at the air-water interface, this reaction is much less understood. We performed systematic Born-Oppenheimer molecular dynamics (BOMD) simulations to study the reaction of various organic acids with SO3 on a water droplet. The results show that with the involvement of interfacial water molecules, organic acids can react with SO3 and form the ion pair of sulfuric-carboxylic anhydride and hydronium. This mechanism is in contrast to the gas-phase reaction mechanisms in which the organic acid either serves as a catalyst for the reaction between SO3 and H2 O or reacts with SO3 directly. The distinct reaction at the water surface has important atmospheric implications, for example, promoting water condensation, uptaking atmospheric condesation species, and incorporating "SO42- " into organic species in aerosol particles. Therefore, this reaction, typically occurring within a few picoseconds, provides another pathway towards aerosol formation.

Different landscapes in a river basin make different contributions to non-point source pollution according to the source–sink theory. Changes in landscape pattern have a considerable impact on river water quality. Precise predictions of the future landscape pattern provide strong support for manipulating land use patterns, which is beneficial for sustainable development in the watershed. The Jiulong River Basin in south-eastern China was selected as the study area. The Random Forest classifier, which combined textural characteristics with spectral information, was applied to interpret the landscapes from Landsat images acquired in 1995, 2005 and 2015 in this paper. The overall classification accuracy reached 86%, and the Kappa index was higher than 0.83, which was better than the accuracy of classifiers based on the exclusive use of spectral information. We used a hybrid cellular automaton–Markov (CA–Markov) model to simulate the landscape pattern of the Jiulong River Basin in 2015 and verified the accuracy according to the interpreted landscape classification map in 2015. The pixels that were predicted to the correct landscape account for 88.35% of total pixels, and the Kappa coefficient was 0.88, indicating that the CA–Markov model was credible for predicting the future landscape pattern in the Jiulong River Basin. The CA–Markov model was applied to forecast the landscape pattern of this watershed in 2025, and the transition area matrix from 2015 to 2025 was obtained. The predicted results demonstrated the imbalanced migration of source–sink landscapes in the future, which indicated the deterioration of water quality in the study area. Hence, government regulators need rational manipulation of the landscape pattern for sustainable development in the Jiulong River Basin.

Both iodic acid (HIO3, IA) and methanesulfonic acid (CH3S(O)2OH, MSA) have been identified by field studies as important precursors of new particle formation (NPF) in marine areas. However, the mechanism of NPF in which IA and MSA are jointly involved is still unclear. Hence, we investigated the IA-MSA nucleation system under different atmospheric conditions and uncovered the corresponding nucleating mechanism at a molecular level for the first time using quantum chemical approach and Atmospheric Cluster Dynamics Code (ACDC). The findings showed that MSA can stabilize IA clusters via both hydrogen and halogen bonds. Moreover, the joint nucleation rate of IA-MSA system is significantly higher than that of IA self-nucleation, particularly in relatively cold marine regions with sparse IA and rich MSA. For the IA-MSA nucleation mechanism, in addition to self-nucleation of IA, the IA-MSA-involved clusters can also directly participate in the nucleation process, and their contribution is particularly prominent in the polar regions with rich MSA and sparse IA. The IA-MSA nucleation mechanism revealed in this work may help to elucidate some missing sources of marine NPF.

Carbon dioxide is considered an inert gas that rarely participates in atmospheric chemical reactions. However, we show here that CO2 is involved in some important photo-oxidation reactions in the atmosphere through the formation of carbonate radicals (CO3∙-). This potentially active intermediate CO3∙- is routinely overlooked in atmospheric chemistry regarding its effect on sulfate formation. Present work demonstrates that SO2 uptake coefficient is enhanced by 17 times on mineral dust particles driven by CO3∙-. It can be produced through two routes over mineral dust surfaces: i) hydroxyl radical + CO32-; ii) holes (h+) + CO32-. Employing a suite of laboratory investigations of sulfate formation in the presence of carbonate radical on the model and authentic dust particles, field measurements of sulfate and (bi)carbonate ions within ambient PM, together with density functional theory (DFT) calculations for single electron transfer processes in terms of CO3∙--initiated S(IV) oxidation, a new role of carbonate radical in atmospheric chemistry is elucidated.

Comprehensive investigations of the possible formation pathways of sulfate, the main composition of atmospheric aerosol in marine areas, continue to challenge atmospheric chemists. As one of the most important oxidation routes of S(iv) contributing to sulfate formation, the reaction process of S(iv) oxidized by hypobromic acid, which is ubiquitous with the gas-phase mixing ratios of ∼310 ppt and has a well-known oxidative capacity, has attracted wide attention. However, little information is available about the detailed reaction mechanism. Especially, due to the abundant species in cloud water, the potential effect of these compositions on these reaction processes and the corresponding effect mechanism are also uncertain. Using high-level quantum chemical calculations, we theoretically elucidate the two-step mechanism of Br+ transfer proposed by experiment through the verification of the key BrSO3- intermediate formation and subsequent hydrolysis reaction or the uncovered reaction of BrSO3- intermediate with OH-. Further, the novel and more competitive mechanisms (OH+ or O atom transfer pathways) that have not been considered in previous studies, leading to sulfate formation directly, have been found. Furthermore, it should be mentioned that we revealed the effect mechanism of constituents catalyzed in cloud water, especially the important H2O-catalyzed mechanism. In addition, all the above pathways follow this catalytic mechanism. This finding indicates a linkage between the complex nature of the atmospheric constituents and related atmospheric reaction, as well as the enhanced occurrence of atmospheric secondary sulfate formation in the atmosphere. Hence, this exploration of sulfate formation related to hypobromic acid could provide a better understanding about the sources of sulfate in marine areas.

Marine aerosols play an important role in the global aerosol system. In polluted coastal regions, ultra-fine particles have been recognized to be related to iodine-containing species and is more serious due to the impact of atmospheric pollutants. Many previous studies have identified iodine pentoxide (I