Biogenic methane in coastal unconsolidated sediment systems: A review.

Marine sediments are the world's largest known reservoir of methane. In many coastal regions, methane is trapped in sediments buried at depths ranging from centimeters to hundreds of meters below the seafloor, in the forms of gas pockets, dispersed gas bubbles and dissolved gas, also known as shallow gas (methane-dominated gas mixture). The existence of shallow gas affects the engineering geological environment and threatens the safety of artificial facilities. The escape of shallow gas from sediments into the atmosphere can even threaten ecosystem security and affect global climate change. However, until now, shallow gas has remained a mystery to the scientific community. For example, how it is generated, how it distributes and migrates in sediments, and what are the factors that influence these processes that are still unclear. In the context of increasingly intense offshore development and global warming, there is a huge gap between existing scientific understanding of shallow gas and the need to develop scientific solutions for related problems. Based on this, this paper systematically collects the information on all aspects of shallow gas mentioned above, comprehensively summarizes the current scientific understanding, and analyzes the existing shortcomings, which will provide systematic references for the research on environmental disaster prevention, engineering technology, climate change, and other fields.

Nitrogen-Containing Compounds Enhance Light Absorption of Aromatic-Derived Brown Carbon.

The formation of secondary brown carbon (BrC) is chemically complex, leading to an unclear relationship between its molecular composition and optical properties. Here, we present an in-depth investigation of molecular-specific optical properties and aging of secondary BrC produced from the photooxidation of ethylbenzene at varied NOx levels for the first time. Due to the pronounced formation of unsaturated products, the mass absorption coefficient (MAC) of ethylbenzene secondary organic aerosols (ESOA) at 365 nm was higher than that of biogenic SOA by a factor of 10. A high NOx level ([ethylbenzene]0/[NOx]0 < 10 ppbC ppb-1) was found to significantly increase the average MAC300-700nm of ESOA by 0.29 m2 g-1. The data from two complementary high-resolution mass spectrometers and quantum chemical calculations suggested that nitrogen-containing compounds were largely responsible for the enhanced light absorption of high-NOx ESOA, and multifunctional nitroaromatic compounds (such as C8H9NO3 and C8H9NO4) were identified as important BrC chromophores. High-NOx ESOA underwent photobleaching upon direct exposure to ultraviolet light. Photolysis did not lead to the significant decomposition of C8H9NO3 and C8H9NO4, indicating that nitroaromatic compounds may serve as relatively stable nitrogen reservoirs and would effectively absorb solar radiation during the daytime.

Molecular size of surfactants affects their degree of enrichment in the sea spray aerosol formation.

Sea spray aerosol (SSA), the largest source of natural primary aerosol, plays an important role in atmospheric chemical processes and the earth radiation balance. Its formation process is controlled by many factors. In this study, ethylene glycol (EG) and polyethylene glycol (PEG) with three different molecular weights (200, 400, 600) were used to investigate the influence of molecular size on the properties of submicron SSA produced by plunging jet from an adjustable home-built SSA generator. Different parameters were tested to obtain the optimum experimental conditions. The addition of EG and PEG inhibited the production of SSA and increased the geometric mean diameter (GMD) between 10 and 35 nm. However, PEG with a molecular weight of 600 could promote the production of SSA at higher concentrations, which means that the molecular weight and concentration of the polymer would affect the production efficiency of SSA. Combining with the measurement of surface tension, we found no clear relationship between surface tension and the yield of SSA, due to the properties of the substances themselves. Transmission electron microscopy images show that the addition of EG and PEG could significantly change the structure of salt nuclei in SSA. PEG was significantly enriched in SSA (with enrichment factors within the range 92.9-133.4), and the enrichment was independent of the sampling time, while increasing with the increase of molecular weight. Our results highlight the influence of polymer molecular weight on the properties of SSA, and their importance to improve the accuracy of aerosol emission model parameters.

Seasonal variation of water-soluble brown carbon in Qingdao, China: Impacts from marine and terrestrial emissions.

Brown carbon (BrC) has been attracting more and more attention owing to its significant effects on climate. However, the limited knowledge on its chemical composition and sources limits the precision of aerosol radiative forcing estimated by climate models. In this study, the chemical components of PM2.5 and optical properties of water-soluble BrC (WS-BrC) were investigated from atmospheric particles collected in summer and winter in Qingdao, China. On the whole, though there were slight diurnal variations, seasonal differences were more obvious. Due to the influence of emission sources and meteorological conditions, the heavier pollution of carbonaceous aerosols occurred in winter. By comparison, the absorption Ångström exponent (AAE) and mass absorption efficiency of WS-BrC at 365 nm (MAE365) showed that WS-BrC in winter had stronger wavelength dependence and light absorption capacity, which might be associated with biomass burning source contributions. This was further confirmed by a strong correlation between the light absorption coefficient at 365 nm (Abs365) and non-sea salt K+, an indicator for biomass burning emissions. Four fluorescent components (C1∼C4) with high unsaturation in water-soluble organic carbon (WSOC) were identified by excitation-emission matrix fluorescence spectroscopy combined with parallel factor analysis method, which showed that WSOC in Qingdao was mainly related to humic-like chromophores. It is worth noting that C1 was similar to the water-soluble chromophore of simulated marine aerosols, which proved that marine emissions do have a certain impact on atmospheric particulate matter in coastal areas. In addition, the results of source analysis showed that WS-BrC originated from different terrestrial sources in different seasons. The current results may help to improve the knowledge of optical properties of WS-BrC in coastal cities, optimize the global climate model and formulate air management policies.

Assessing the influence of environmental conditions on secondary organic aerosol formation from a typical biomass burning compound.

The atmospheric chemistry in complex air pollution remains poorly understood. In order to probe how environmental conditions can impact the secondary organic aerosol (SOA) formation from biomass burning emissions, we investigated the photooxidation of 2,5-dimethylfuran (DMF) under different environmental conditions in a smog chamber. It was found that SO2 could promote the formation of SOA and increase the amounts of inorganic salts produced during the photooxidation. The formation rate of SOA and the corresponding SOA mass concentration increased gradually with the increasing DMF/OH ratio. The addition of (NH4)2SO4 seed aerosol accelerated the SOA formation rate and significantly shortened the time for the reaction to reach equilibrium. Additionally, a relatively high illumination intensity promoted the formation of OH radicals and, correspondingly, enhanced the photooxidation of DMF. However, the enhancement of light intensity accelerated the aging of SOA, which led to a gradual decrease of the SOA mass concentration. This work shows that by having varying influence on atmospheric chemical reactions, the same environmental factor can affect SOA formation in different ways. The present study is helpful for us to better understand atmospheric complex pollution.

Water-soluble matter in PM2.5 in a coastal city over China: Chemical components, optical properties, and source analysis.

Although marine and terrestrial emissions simultaneously affect the formation of atmospheric fine particles in coastal areas, knowledge on the optical properties and sources of water-soluble matter in these areas is still scarce. In this work, taking Qingdao, China as a typical coastal location, the chemical composition of PM2.5 during winter 2019 was analyzed. Excitation-emission matrix fluorescence spectroscopy was combined with parallel factor analysis model to explain the components of water-soluble atmospheric chromophores of PM2.5. Our analysis indicated that NO3-, NH4+ and SO42- ions accounted for 86.80% of the total ion mass, dominated by NO3-. The ratio of [NO3-]/[SO42-] was up to 2.42 ± 0.84, suggesting that mobile sources play an important role in local pollutants emission. The result of positive correlation between Abs365 with K+ suggests that biomass burning is an important source of water-soluble organic compounds (WSOC). Six types of fluorophores (C1-C6), all humic-like substances, were identified in WSOC. Humification index, biological index and fluorescence index in winter were 1.66 ± 0.34, 0.51 ± 0.44 and 1.09 ± 0.78, respectively, indicating that WSOC in Qingdao were mainly terrestrial organic matters. Overall, although the study area is close to the ocean, the contribution of terrestrial sources to PM2.5, especially vehicle exhaust and coal combustion, is still much higher than that of marine sources. Our study provides a more comprehensive understanding of chemical and optical properties of WSOC based on PM2.5 in coastal areas, and may provide ground for improving local air quality.

Heterogeneous reaction of SO2 on CaCO3 particles: Different impacts of NO2 and acetic acid on the sulfite and sulfate formation.

Despite the heterogeneous reaction of sulfur dioxide (SO2) on mineral dust particles significantly affects the atmospheric environment, the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear. In this work, using the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique, we employed a mineral dust particle model (CaCO3) combined with NO2 and acetic acid to investigate their effects on the heterogeneous reaction of SO2 on CaCO3 particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate. The addition of NO2 or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly. There was a synergistic effect between NO2 and SO2 that promoted the oxidation of sulfite to sulfate, and a competitive effect between acetic acid and SO2 that inhibited the formation of sulfite. Moreover, light and water vapor can also affect the heterogeneous reaction of SO2 with the coexistence of multiple gases. These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.

Anthropogenic-Biogenic Interactions at Night: Enhanced Formation of Secondary Aerosols and Particulate Nitrogen- and Sulfur-Containing Organics from ß-Pinene Oxidation.

Mixing of anthropogenic gaseous pollutants and biogenic volatile organic compounds impacts the formation of secondary aerosols, but still in an unclear manner. The present study explores secondary aerosol formation via the interactions between ß-pinene, O3, NO2, SO2, and NH3 under dark conditions. Results showed that aerosol yield can be largely enhanced by more than 330% by NO2 or SO2 but slightly enhanced by NH3 by 39% when the ratio of inorganic gases to ß-pinene ranged from 0 to 1.3. Joint effects of NO2 and SO2 and SO2 and NH3 existed as aerosol yields increased with NO2 but decreased with NH3 when SO2 was kept constant. Infrared spectra showed nitrogen-containing aerosol components derived from NO2 and NH3 and sulfur-containing species derived from SO2. Several particulate organic nitrates (MW 215, 229, 231, 245), organosulfates (MW 250, 264, 280, 282, 284), and nitrooxy organosulfates (MW 295, 311, 325, 327, and 343) were identified using high-resolution orbitrap mass spectrometry in NO2 and SO2 experiments, and their formation mechanism is discussed. Most of these nitrogen- and sulfur-containing species have been reported in ambient particles. Our results suggest that the complex interactions among ß-pinene, O3, NO2, SO2, and NH3 during the night might serve as a potential pathway for the formation of particulate nitrogen- and sulfur-containing organics, especially in polluted regions with both anthropogenic and biogenic influences.

Reply to the 'comment on "impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products"' by R. Chow, D. K. W. Mok, E. P. F. Lee and J. M. Dyke, Phys. Chem. Chem. Phys., 2021, 23, DOI.

We reply to the comment on our recent paper entitled "Impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products" by Chow et al. In their comment, the authors raised the differences between our results and their results in an earlier paper (R. Chow, D. K. W. Mok, E. P. F. Lee and J. M. Dyke, Phys. Chem. Chem. Phys., 2016, 18, 30554-30569), in terms of kinetics and potential energy surface, and they attributed these differences to the use of a small integration grid size and closed-shell wavefunctions for geometry optimizations in our study. Indeed, in our original manuscript, we did not ensure the proper use of UHF wavefunctions for singlet states, which led the singlet states to be treated with restricted M06-2X wavefunctions during optimizations. Furthermore, the default integration grid was used. New geometry optimizations have been performed where reactant complexes on the singlet surface were treated in their open-shell singlet states (ensured by using unrestricted-spin wave-functions) and using very tight convergence criteria, and new reaction rate constants have been calculated based on new energy barriers. No barrierless hydrogen abstraction reactions were observed as reported in our previous results and, consequently, the outer rate coefficient in the two-transition state approach (given by eqn (5) in Tsona et al., 2019) was determined by the collision theory. Overall rate constants exhibit a negative temperature dependency in the 200-400 K range. Despite the changes on the reaction energies and kinetics due to wrong UHF wavefunctions, our main conclusion that water has no net effect on the BrO + HO2 → BrOH + O2 reaction is still valid.

Effect of NOx and SO2 on the photooxidation of methylglyoxal: Implications in secondary aerosol formation.

Methylglyoxal (CH3COCHO, MG), which is one of the most abundant α-dicarbonyl compounds in the atmosphere, has been reported as a major source of secondary organic aerosol (SOA). In this work, the reaction of MG with hydroxyl radicals was studied in a 500 L smog chamber at (293 ± 3) K, atmospheric pressure, (18 ± 2)% relative humidity, and under different NOx and SO2. Particle size distribution was measured by using a scanning mobility particle sizer (SMPS) and the results showed that the addition of SO2 can promote SOA formation, while different NOx concentrations have different influences on SOA production. High NOx suppressed the SOA formation, whereas the particle mass concentration, particle number concentration and particle geometric mean diameter increased with the increasing NOx concentration at low NOx concentration in the presence of SO2. In addition, the products of the OH-initiated oxidation of MG and the functional groups of the particle phase in the MG/OH/SO2 and MG/OH/NOx/SO2 reaction systems were detected by gas chromatography mass spectrometry (GC-MS) and attenuated total reflection fourier transformed infrared spectroscopy (ATR-FTIR) analysis. Two products, glyoxylic acid and oxalic acid, were detected by GC-MS. The mechanism of the reaction of MG and OH radicals that follows two main pathways, H atom abstraction and hydration, is proposed. Evidence is provided for the formation of organic nitrates and organic sulfate in particle phase from IR spectra. Incorporation of NOx and SO2 influence suggested that SOA formation from anthropogenic hydrocarbons may be more efficient in polluted environment.

Impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products.

The BrO + HO2 reaction, which participates in the cycle of ozone removal via BrOH formation, was explored both in the absence and in the presence of water using ab initio calculations. Two main sets of products, (i) HBr + O3 and (ii) BrOH + O2, are formed regardless of the presence of water, following a hydrogen abstraction mechanism. The HBr + O3 products are formed from the intermediate BrOOOH adduct, whereas BrOH + O2 are formed either from the intermediate OBrOOH adduct or via a barrierless hydrogen transfer from HO2 to BrO. Owing to the formation of molecular oxygen that can bear different spin configurations, the formation of BrOH + O2 products was examined both on the singlet and the triplet surfaces. Under relevant atmospheric temperatures and pressure, the formation of products (i) is energetically and kinetically less favorable than that of products (ii). The rate coefficient at 298 K for the HBr + O3 formation was determined to be 2.00 × 10-20 cm3 molecule-1 s-1, and found to decrease by 1-2 orders of magnitude when one or both reactants are clustered with water. For the formation of BrOH + O2, a rate coefficient of 2.21 × 10-11 cm3 molecule-1 s-1 is determined on both singlet and triplet surfaces in the absence of water. Though this rate coefficient slightly decreases for the hydrated reactions, the fractions of the reactants that are effectively complexed with water are not high enough to shift the overall BrOH + O2 formation rate. The current study further indicates that humidity plays a negligible role in ozone removal via the BrO + HO2 reaction.

Elucidating the mechanism and kinetics of the water-assisted reaction of nitrous acid with hydroxyl radical.

The effect of a single water molecule on the atmospheric reaction between nitrous acid (HONO) and the hydroxyl radical (OH) has been investigated in this work. The CCSD(T)/aug-cc-pVTZ//UωB97X-D/aug-cc-pVTZ level of theory was used to obtain all stationary points on the energy surface and to determine the rate constants. Due to the two HONO configurations (cis- and trans-) existing in the atmosphere, the water-free HONO + OH reaction has two major elementary channels, both based on the HONO hydrogen abstraction by the hydroxyl radical. The products, NO2 + H2O, are formed with substantial energy gain, but separated by relatively low energy barriers. In the presence of water, the reaction becomes more complex, proceeding through twelve different channels, each starting with the formation of a binary complex between water and one reactant followed by its interaction with the third species. The products are similar to those of the water-free reaction. At 298 K, the rate constants of water-free cis-HONO + OH and trans-HONO + OH reactions are 1.34 × 10-12 and 1.00 × 10-15 cm3 molecule-1 s-1, respectively. The calculated rate constants for H2O-complexed HONO or OH increase by one to two orders of magnitude, but weighted by their relative abundances, the H2O-complexed fractions of the reactants in the atmosphere are so small that the effect of H2O on the overall reaction rate is minor.

Effect of a single water molecule on the HO2 + ClO reaction.

The catalytic effect of a single water molecule on the HO2 + ClO reaction has been investigated at the CCSD(T)/aug-cc-pVTZ//B3LYP-D3/aug-cc-pVDZ level of theory. Four H-abstraction paths and two kinds of products, among which the paths for HOCl + O2 formation are dominant, have been found for the HO2 + ClO reaction without water. The rate constant of the most favorable path for the reaction without water is computed to be 4.53 × 10-12 cm3 molecule-1 s-1 at room temperature, in good agreement with the experiment. In the presence of a water molecule, although the reaction becomes more complex, the dominant products do not change. Four main channels, starting from HO2H2O + ClO, H2OHO2 + ClO, ClOH2O + HO2 and H2OClO + HO2, are investigated. The most favorable paths, reactions between H2OHO2 and ClO, and between ClOH2O and HO2, are 7-10 and 6-9 orders of magnitude slower than the reaction in the absence of water, respectively. It is concluded that the presence of a single water molecule does not play an important role in enhancing the HO2 + ClO reaction under tropospheric conditions.

From O2--Initiated SO2 Oxidation to Sulfate Formation in the Gas Phase.

We have investigated the chemical fate of O2SOO-, the immediate product of the reaction between sulfur dioxide (SO2) and the superoxide ion (O2-), by reactions with nitrogen oxides (NO and NO2) using high-level theoretical calculations. Both reactions with NO and NO2 lead to exergonic formation of adducts, which subsequently overcome low energy barriers to form SO3 + NO3- and SO4- + NO, with rate constants of 6.9 × 10-10 and 6.3 × 10-10 cm3 molecule-1 s-1, respectively. Reactions with water are ∼15-23 times slower than corresponding naked reactions at ambient conditions, hence not slow enough to be prevented at these conditions. The studied reactions not only are useful for understanding ionic SO2 oxidation in the atmosphere and in chamber experiments but also provide a new mechanism for the gas-phase formation of sulfate from an ion-induced mechanism. These reactions may enhance our understanding of the early stages of secondary aerosol formation.

Gas-Phase Oxidation of Allyl Acetate by O3, OH, Cl, and NO3: Reaction Kinetics and Mechanism.

Allyl acetate (AA) is widely used as monomer and intermediate in industrial chemicals synthesis. To evaluate the atmospheric outcome of AA, kinetics and mechanism of its gas-phase reaction with main atmospheric oxidants (O3, OH, Cl, and NO3) have been investigated in a Teflon reactor at 298 ± 3 K. Both absolute and relative rate methods were used to determine the rate constants for AA reactions with the four atmospheric oxidants. The obtained rate constants (in units of cm3 molecule-1 s-1) are (1.8 ± 0.3) × 10-18, (3.1 ± 0.7) × 10-11, (2.5 ± 0.5) × 10-10, and (1.1 ± 0.4) × 10-14, for reactions with O3, OH, Cl, and NO3, respectively. While results for reactions with O3, OH and Cl are in good agreement with previous studies, the kinetics for the reaction with NO3 is reported for the first time in this study. On the basis of determined rate constants, the tropospheric lifetimes of AA are τO3 = 9 days, τOH = 5 h, τCl = 5 days, τNO3 = 2 days. On the basis of the products study, reaction mechanisms for these oxidations have been proposed and the reaction products were detected using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and Fourier transform infrared spectroscopy (FTIR). Results show that the main products formed in these reactions are carbonyl compounds. In particular, 2-oxoethyl acetate was detected in all four AA oxidation reactions. Compared to previous studies, several new products were determined for reactions with OH and Cl. These results form a set of comprehensive kinetic data for AA reactions with main atmospheric oxidants and provide a better understanding of the degradation and atmospheric outcome of unsaturated acetate esters in the troposphere, during both daytime and nighttime.

The Role of (H2O)1-2 in the CH2O + ClO Gas-Phase Reaction.

Mechanism and kinetic studies have been carried out to investigate whether one and two water molecules could play a possible catalytic role on the CH2O + ClO reaction. Density functional theory combined with the coupled cluster theory were employed to explore the potential energy surface and the thermodynamics of this radical-molecule reaction. The reaction proceeded through four different paths without water and eleven paths with water, producing H + HCO(O)Cl, Cl + HC(O)OH, HCOO + HCl, and HCO + HOCl. Results indicate that the formation of HCO + HOCl is predominant both in the water-free and water-involved cases. In the absence of water, all the reaction paths proceed through the formation of a transition state, while for some reactions in the presence of water, the products were directly formed via barrierless hydrogen transfer. The rate constant for the formation of HCO + HOCl without water is 2.6 × 10-16 cm³ molecule-1 s-1 at 298.15 K. This rate constant is decreased by 9-12 orders of magnitude in the presence of water. The current calculations hence demonstrate that the CH2O + ClO reaction is impeded by water.

Role of water on the H-abstraction from methanol by ClO.

The influence of a single water molecule on the reaction mechanism and kinetics of hydrogen abstraction from methanol (CH3OH) by the ClO radical has been investigated using ab initio calculations. The reaction proceeds through two channels: abstraction of the hydroxyl H-atom and methyl H-atom of CH3OH by ClO, leading to the formation of CH3O+HOCl (+H2O) and CH2OH+HOCl (+H2O), respectively. In both cases, pre- and post-reactive complexes were located at the entrance and exit channel on the potential energy surfaces. Results indicate that the formation of CH2OH+HOCl (+H2O) is predominant over the formation of CH3O+HOCl (+H2O), with ambient rate constants of 3.07×10-19 and 3.01×10-23cm3/(molecule·sec), respectively, for the reaction without water. Over the temperature range 216.7-298.2K, the presence of water is seen to effectively lower the rate constants for the most favorable pathways by 4-6 orders of magnitude in both cases. It is therefore concluded that water plays an inhibitive role on the CH3OH+ClO reaction under tropospheric conditions.

Gas-Phase Reaction of Methyl n-Propyl Ether with OH, NO3, and Cl: Kinetics and Mechanism.

Rate constants at room temperature (293 ± 2 K) and atmospheric pressure for the reaction of methyl n-propyl ether (MnPE), CH3OCH2CH2CH3, with OH and NO3 radicals and the Cl atom have been determined in a 100 L FEP-Teflon reaction chamber in conjunction with gas chromatography-flame ionization detector (GC-FID) as the detection technique. The obtained rate constants k (in units of cm3 molecule-1 s-1) are (9.91 ± 2.30) × 10-12, (1.67 ± 0.32) × 10-15, and (2.52 ± 0.14) × 10-10 for reactions with OH, NO3, and Cl, respectively. The products of these reactions were investigated by gas chromatography-mass spectrometry (GC-MS), and formation mechanisms are proposed for the observed reaction products. Atmospheric lifetimes of the studied ether, calculated from rate constants of the different reactions, reveal that the dominant loss process for MnPE is its reaction with OH, while in coastal areas and in the marine boundary layer, MnPE loss by Cl reaction is also important.

A Closure Study of the Reaction between Sulfur Dioxide and the Sulfate Radical Ion from First-Principles Molecular Dynamics Simulations.

In a previous study, we applied quantum chemical methods to study the reaction between sulfur dioxide (SO2) and the sulfate radical ion (SO4(-)) at atmospheric relevant conditions and found that the most likely reaction product is SO3SO3(-). In the current study, we investigate the chemical fate of SO3SO3(-) by reaction with ozone (O3) using first-principles molecular dynamics collision simulations. This method assesses both dynamic and steric effects in the reactions and therefore provides the most likely reaction pathways. We find that the majority of the collisions between SO3SO3(-) and O3 are nonsticking and that the most frequent reactive collisions regenerate sulfate radical ions and produce sulfur trioxide (SO3) while ejecting an oxygen molecule (O2). The rate of this reaction is determined to be 2.5 × 10(-10) cm(3) s(-1). We then conclude that SO4(-) is a highly efficient catalyst in the oxidation of SO2 by O3 to SO3.

Structures, Hydration, and Electrical Mobilities of Bisulfate Ion-Sulfuric Acid-Ammonia/Dimethylamine Clusters: A Computational Study.

Despite the well-established role of small molecular clusters in the very first steps of atmospheric particle formation, their thermochemical data are still not completely available due to limitation of the experimental techniques to treat such small clusters. We have investigated the structures and the thermochemistry of stepwise hydration of clusters containing one bisulfate ion, sulfuric acid, base (ammonia or dimethylamine), and water molecules using quantum chemical methods. We found that water facilitates proton transfer from sulfuric acid or the bisulfate ion to the base or water molecules, and depending on the hydration level, the sulfate ion was formed in most of the base-containing clusters. The calculated hydration energies indicate that water binds more strongly to ammonia-containing clusters than to dimethylamine-containing and base-free clusters, which results in a wider hydrate distribution for ammonia-containing clusters. The electrical mobilities of all clusters were calculated using a particle dynamics model. The results indicate that the effect of humidity is negligible on the electrical mobilities of molecular clusters formed in the very first steps of atmospheric particle formation. The combination of the results of this study with those previously published on the hydration of neutral clusters by our group provides a comprehensive set of thermochemical data on neutral and negatively charged clusters containing sulfuric acid, ammonia, or dimethylamine.