Enrichment of short-chain organic acids transferred to submicron sea spray aerosols.

Organic acids, considered to be a substantial component of the marine carbon cycle, can enter the atmosphere through sea spray aerosol (SSA) and further affect the climate. Despite their importance, the distribution and mixing state of organic acids in SSA over the marine boundary layer are poorly understood and therefore need more investigation. Here, we have used ion chromatography (IC) in anion mode to measure short-chain organic acids concentrations in SSA collected throughout a custom-made SSA simulation chamber.

Water-soluble matter in PM 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 PM 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 PM.

Heterogeneous reaction of SO on CaCO particles: Different impacts of NO and acetic acid on the sulfite and sulfate formation.

Despite the heterogeneous reaction of sulfur dioxide (SO) 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 (CaCO) combined with NO and acetic acid to investigate their effects on the heterogeneous reaction of SO on CaCO particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate.

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 SO could promote the formation of SOA and increase the amounts of inorganic salts produced during the photooxidation.

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 PM and optical properties of water-soluble BrC (WS-BrC) were investigated from atmospheric particles collected in summer and winter in Qingdao, China.

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 NO 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.

Atmospheric chemical processes of microcystin-LR at the interface of sea spray aerosol.

Microcystins are the most toxic toxins released by cyanobacteria and they have adverse effects on aquatic ecosystems and even human health. Although the removal and detoxification of microcystins in various water bodies have been extensively studied, the interaction mechanism and reaction process of microcystins once they enter the atmosphere are largely unknown, especially at the organic-enriched sea spray aerosol (SSA) interface. Herein, using the surface technique of Langmuir trough coupled in-situ infrared reflection-absorption spectra, we studied the interfacial behavior of microcystin-LR (MC-LR) in artificial seawater containing humic acid and typical surfactants in the presence or absence of UV-irradiation.

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.

Relative Humidity Changes the Role of SO in Biogenic Secondary Organic Aerosol Formation.

SO influences secondary organic aerosol (SOA) and organosulfates (OSs) formation but mechanisms remain elusive. This study focuses on this topic by investigating biogenic γ-terpinene ozonolysis under various SO and relative humidity (RH) conditions. With a constant SO concentration (∼110 ppb), the increase in RH transformed SO sinks from stabilized Criegee intermediates (sCIs) to peroxides in aerosol particles.

Enhanced photocatalytic performance of PdO-loaded heterostructured nanobelts to degrade phenol.

Heterostructured catalysts play a significant role in the photodegradation of pollutants in wastewater. Combining the large surface of nanobelts with the high photocatalytic property of titanium dioxide (TiO) nanoparticles is a promising method for preparing photocatalysts, which have an advanced photocatalytic activity and are easy to precipitate. In this work, titanium dioxide nanobelts (NB) and acid corroded titanium dioxide nanobelts (C-NB) were synthesized via a hydrothermal process under alkaline conditions.

Anthropogenic-Biogenic Interactions at Night: Enhanced Formation of Secondary Aerosols and Particulate Nitrogen- and Sulfur-Containing Organics from β-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 β-pinene, O, NO, SO, and NH under dark conditions. Results showed that aerosol yield can be largely enhanced by more than 330% by NO or SO but slightly enhanced by NH by 39% when the ratio of inorganic gases to β-pinene ranged from 0 to 1.

Unraveling interfacial properties of organic-coated marine aerosol with lipase incorporation.

Marine aerosols are believed to have an organic surface coating on which fatty acids act as an important component due to their high surface activity. In addition, various kinds of enzyme species are abundantly found in seawater, some of which have been identified to exist in marine aerosols. Herein, from the perspective of marine aerosol interface simulation, we investigate the effect of Burkholderia cepacia lipase on the surface properties of stearic acid (SA) monolayer at the air-water interface by using surface-sensitive techniques of Langmuir trough and Infrared reflection-absorption spectroscopy (IRRAS).

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

Influence of Water on the Gas-Phase Reaction of Dimethyl Sulfide with BrO in the Marine Boundary Layer.

The effect of a single water molecule on the reaction of dimethyl sulfide (DMS) with BrO reaction has been investigated using quantum chemical calculations at the CCSD(T)/6-311++G**//BH&HLYP/aug-cc-pVTZ level of theory. Two reaction mechanisms have been considered both in the absence and the presence of water, namely, oxygen atom transfer and hydrogen abstraction, among which the oxygen atom transfer was predominant. Five reaction channels were found in the absence of water, in which the channels starting from the -configuration of the pre-reaction complexes were more favorable because of the low energy barrier.

Aqueous-phase oxidation of syringic acid emitted from biomass burning: Formation of light-absorbing compounds.

Syringic acid is a methoxyphenol model compound derived from biomass burning, and its photooxidation processes have important effects on atmospheric chemistry. However, its aqueous-phase photochemistry remains unclear. In this study, we systematically report the photooxidation of syringic acid induced by OH radicals in the aqueous phase.

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

Methylglyoxal (CHCOCHO, 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 SO. Particle size distribution was measured by using a scanning mobility particle sizer (SMPS) and the results showed that the addition of SO can promote SOA formation, while different NOx concentrations have different influences on SOA production.

Effects of NO and SO on the secondary organic aerosol formation from the photooxidation of 1,3,5-trimethylbenzene: A new source of organosulfates.

1,3,5-Trimethylbeneze (TMB) is an important constituent of anthropogenic volatile organic compounds that contributes to the formation of secondary organic aerosol (SOA). A series of chamber experiments were performed to probe the effects of NO and SO on SOA formation from TMB photooxidation. The molecular composition of TMB SOA was investigated by ultra-high performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS).

Sea spray aerosol formation: Results on the role of different parameters and organic concentrations from bubble bursting experiments.

Submicron sea spray aerosol (SSA) particles play an essential role in atmospheric chemical processes and the Earth's radiative balance. In this study, different combinations of NaCl, MgSO, malonic acid (MA), d-fructose and sodium malonate were used to explore the effect of MA on submicron SSA generation. SSA particles were produced at room temperature by bubble bursting from an adjustable home-built SSA generator with sintered glass filters.

Effects of NO and SO on the heterogeneous reaction of acetic acid on α-AlO in the presence and absence of simulated irradiation.

The effects of NO2 and SO2 on the atmospheric heterogeneous reaction of acetic acid on α-Al2O3 in the presence and absence of simulated irradiation were investigated at ambient conditions by using the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique. The experiment was divided into two parts: the heterogeneous reaction experiment and the pre-adsorption reaction experiment under light and dark conditions. In the heterogeneous reaction experiment, solar radiation stimulates the formation of more acetate and nitrate.

Competitive reactions of SO and acetic acid on α-AlO and CaCO particles.

Heterogeneous reactions between gaseous pollutants and mineral particles have gradually become a research hotspot in the field of atmospheric chemistry. In this paper, competitive reactions between SO and acetic acid on the surface of α-AlO and CaCO particles were studied by the diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) technique in dark and dry conditions. At the same time, the temporary evolution of the integrated absorbance of acetate and sulfite was investigated to further understand the interaction of SO and acetic acid on the mineral particles.

Impact of water on the BrO + HO 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.

Role of (HO) ( = 1-2) in the Gas-Phase Reaction of Ethanol with Hydroxyl Radical: Mechanism, Kinetics, and Products.

The effect of water on the hydrogen abstraction mechanism and product branching ratio of CHCHOH + OH reaction has been investigated at the CCSD(T)/aug-cc-pVTZ//BH&HLYP/aug-cc-pVTZ level of theory, coupled with the reaction kinetics calculations, implying the harmonic transition-state theory. Depending on the hydrogen sites in CHCHOH, the bared reaction proceeds through three elementary paths, producing CHCHOH, CHCHO, and CHCHOH and releasing a water molecule. Thermodynamic and kinetic results indicate that the formation of CHCHOH is favored over the temperature range of 216.

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.

Influence of relative humidity on cyclohexene SOA formation from OH photooxidation.

Secondary organic aerosol (SOA) is a complex mixture consisting of a variety of oxidation products. In this study, the role of relative humidity (RH) on SOA formation with different [HO]/[cyclohexene] was investigated in a smog chamber. It was found that the cyclohexene SOA yield increases with increasing initial OH concentration at both high and low RH conditions.

Effects of NOx, SO and RH on the SOA formation from cyclohexene photooxidation.

We performed a laboratory investigation of the secondary organic aerosol (SOA) formation from cyclohexene photooxidation with different initial NOx and SO concentrations at low and high relative humidity (RH). Both SOA yield and number concentration first increase drastically and then, decreased when the [VOC]/[NOx] ratio changed from 30 to 10 and from 10 to 3. Though the presence of SO could increase the SOA number concentration, the SOA yield could only increase under [VOC]/[NOx] = 10 and high RH, and [VOC]/[NOx] = 3 and low RH experimental conditions, while decreasing under [VOC]/[NOx] = 10 and low RH conditions.