This is a comprehensive study of the physicochemical characterization of multicomponent aerosols in the smoky atmosphere of Moscow during the extreme wildfires of August 2010 and against the background atmosphere of August 2011. Thermal–optical analysis, liquid and ion chromatography, IR spectroscopy, and electron microscopy were used to determine the organic content (OC) and elemental content (EC) of carbon, organic/inorganic and ionic compounds, and biomass burning markers (anhydrosaccharides and the potassium ion) and study the morphology and elemental composition of individual particles. It has been shown that the fires are characterized by an increased OC/EC ratio and high concentrations of ammonium, potassium, and sulfate ions in correlation with an increased content of levoglucosan as a marker of biomass burning. The organic compounds containing carbonyl groups point to the process of photochemical aging and the formation of secondary organic aerosols in the urban atmosphere when aerosols are emitted from forest fires. A cluster analysis of individual particles has indicated that when the smokiest atmosphere is characterized by prevailing soot/tar ball particles, which are smoke-emission micromarkers.

A series of experiments aimed at studying the effect of combustion regimes of typical Siberian biomasses on the optical, microphysical, and physical-chemical properties of smoke aerosols was performed in the Large Aerosol Chambe, Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. A comprehensive data analysis showed that temperature regime of Siberian pine and coniferous tree burning has a key effect on the formation and time dynamics of all smoke characteristics. The polarization spectronephelometer measurements of light scattering are used to determine the size distributions and absorption indices of particles. Particles in the smoldering phase are weakly absorbing, but the mixed phase contains a strongly absorbing fine component produced in open flame phases. We studied microstructure characteristics of aerosols by the analysis of morphology and elemental composition. Groups of soot and organic particles were determined as micromarkers of emissions in open flaming and smoldering phases, respectively. The organic and elemental carbon contents, origin and concentration of chemical compounds in the water-soluble ion fraction exhibit a strong dependence on the combustion phase. Sugar anhydride (levoglucosan) was determined in the smoldering phase as a stable molecular marker of Siberian pine burning. A number of specific markers of coniferous wood burning were identified among the chemical compounds. Smoke aging is accompanied by condensation of organic and inorganic compounds, transformation of aerosol surface chemistry, and the formation of the group of potassium-rich particles, all demonstrating the complexity and variability of the chemical composition and microstructure of atmospheric aerosol pollution during Siberian forest fires.

Raman microspectroscopy (RM), thermo-optical analysis and Fourier transform infrared (FTIR) spectroscopy were used to characterize soot with different organic carbon (OC) content (4%, 47% and 87%), generated with a CAST burner at various propane-to-air ratios. While the FTIR analysis revealed the organic composition of the samples, the RM analysis gave an increased fluorescence background and an additional shoulder in the spectrum with increasing OC content. According to RM data and in agreement with high-resolution transmission electronic microscopy (HRTEM) analysis, the nanostructural order was high for the soot with 4% of OC and low for the soot with 87% of OC. Additionally, a heating stage was used to perform in situ RM analysis during the soot oxidation at temperatures up to 600 degrees C in air. The (fluorescent) organic components were evaporated/transformed or oxidized with increasing temperature (up to 500 degrees C), and the actual soot nanostructure changed significantly. At 600 degrees C the chemical heterogeneity vanished and the structural order increased, since the organic components as well as amorphous carbon were oxidized by that time. These results can help in understanding the relation between the OC content in the soot and its structure, reactivity and impact on the environment. (C) 2016 Elsevier Ltd. All rights reserved.

This is a study of the physical and chemical properties of carbonaceous aerosols emitted by transport systems (namely, by aircraft gas turbine engines and large ship diesel engines) into the atmosphere. A comparative analysis of the morphology, size, elemental composition, and surface chemistry between aviation and diesel soot particles reveals the general and characteristic features of emissions from each source. The high pollution rate of diesel soot particles, considerable fraction of metal admixtures, and availability of char particles characterize the specific features of the formation of particles of this type. The main characteristics characterizing the interaction between aviation and shipping emission aerosols in the moist atmosphere (the composition of organic and water-soluble fractions at the surface) have been obtained. Due to high hygroscopicity, the microparticles can generate cloud condensation nuclei and initiate contrails and additional tropospheric cloudiness.

We use a laboratory approach for the quantification of the water uptake by particles with varying amounts of sulfates to simulate the aging of fossil fuel combustion particles in the atmosphere. Diesel fuel and aviation kerosene laboratory-made soots are chosen as representative of the hydrophobic fraction of diesel and aircraft engine-emitted particulates and commercial carbon blacks are used as surrogates for industry emissions. The transformation of soot hydration properties from hydrophobic, through hydrophilic, to hygroscopic is demonstrated based on the amount of water uptake by the laboratory-produced EC soot covered by sulfates as the amount of sulfate increases. The mechanism of water/soot interaction changes from an adsorption on active sites to a water film formation and to the dissolution of water into the water-soluble sulfate, while the amount of sulfate increases. Laboratory simulations show that coverage of EC soot by organics diminishes the effect of sulfuric acid deposition. We demonstrate that the surface chemical properties and the size of primary particles affect the amount of water taken up by the soot particles and their aging in the atmosphere.

A number of samples that simulate the chemical composition of carbonaceous aerosols emitted by transport into the atmosphere have been synthesized using the method of deposition of organic compounds and sulfuric acid, which are identified in the particulate coverage of diesel and aircraft engine soot particles, onto the surface of elemental carbon. The analysis of water adsorption isotherms allows one to estimate the influence of the surface chemistry of particles on the degree of their hygroscopicity. Water adsorption measurements show that modification of a particle surface by nonpolar organics (aliphatic and aromatic hydrocarbons) leads to the hydrophobization of a soot surface. The impact of polar oxygen-containing organic compounds (ethers, ketones, aromatic, and aliphatic acids) on adsorption capacity with respect to the water of samples that they modify substantially depends on the nature and composition of the hydrophobic part of the molecules. Among the ionic compounds organic acid salts have the most hydrophilization effect, which is comparable with the adsorption capacity of soot with sulfuric acid deposited on its surface. This observation allows one to quantitatively define how the nature of chemical compounds on soot surface influences water adsorption and to estimate the interaction of water molecules with fossil fuel combustion particles in a humid atmosphere.

Black carbon particles emitted by natural and anthropogenic sources of combustion are potential nuclei of ice formation of cirri in troposphere. The freezing of the ensembles of water microdroplets containing black carbon particles of different origins, including those modified with organic substances, is studied. Ice-forming ability is shown to be predetermined by the density and sizes of black carbon agglomerates, as well as the chemistry and wettability of their surface. Ice formation is most efficient in dispersions of black carbon particles that are stable with respect to sedimentation and have a uniform distribution of particles over the droplet volume. In the presence of oxygen-containing groups on the particle surface, freezing temperature increases. The efficiency of the ice formation decreases in the presence of noticeable amounts of water-soluble substances on the particle surface. The maximum freezing ability is inherent in ensembles of water droplets containing hydrophilic particles. Characteristics ensuring a high ice forming ability of nuclei are determined.

To clarify the impact of fossil fuel combustion particles' composition on their capacity to take up water, we apply a laboratory approach in which the method of deposition of compounds, identified in the particulate coverage of diesel and aircraft engine soot particles, is developed. It is found that near-monolayer organic/inorganic coverage of the soot particles may be represented by three groups of fossil fuel combustion-derived particulate matter with respect to their Hansh's coefficients related to hydrophilic properties. Water adsorption measurements show that nonpolar organics (aliphatic and aromatic hydrocarbons) lead to hydrophobization of the soot surface. Acidic properties of organic compounds such as those of oxidized PAHs, ethers, ketones, aromatic, and aliphatic acids are related to higher water uptake, whereas inorganic acids and ionic compounds such as salts of organic acids are shown to be responsible for soot hydrophilization. This finding allows us to quantify the role of the chemical identity of soot surface compounds in water uptake and the water interaction with fossil fuel combustion particles in the humid atmosphere.

2,000 water droplets with soot particles immersed are monitored individually to establish the link between physico-chemical properties and freezing efficiency. Soot behaviour in water (relating with number density and agglomerate size), wetting, and water soluble fraction (WSF) are found as key parameters defining the freezing temperature. The maximum freezing efficiency, 6°C, is reported for homogeneously distributed low size soot agglomerates of low number density and with hydrophilic coverage.