[High-Throughput Sequencing Analysis of Microbial Communities in Summertime Atmospheric Particulate Matter in Hefei City].

The composition, physical and chemical properties, sources, and temporal and spatial changes in airborne particulate matter have been extensively investigated in previous studies. However, less is known about bioaerosols, which are mainly composed of bacteria and fungi and constitute up to 25% of the total airborne particulate matter. In this study, we used inductively coupled plasma mass spectrometry and ion chromatography to determine the concentrations of trace elements and water-soluble ions in atmospheric particulates, respectively. These analyses were combined with high-throughput sequencing methods and real-time quantitative polymerase chain reaction to analyze the microbial compositions in PM1.0, PM2.5, and PM10 samples, which were collected from July to September in Hefei City. The results showed that there were no significant differences in the bacterial community diversity across the three size fractions (analysis of variance (ANOVA), P>0.05). The bacterial and fungal community diversities on sunny days were lower than those on rainy days, and the bacterial community diversity in all samples was significantly higher than the fungal community diversity (ANOVA, P<0.01). The predominant bacterial phyla were Proteobacteria (46.19%), Firmicutes (33.42%), Bacteroidetes (10.99%), Cyanobacteria (3.33%), and Actinobacteria (2.11%). Ascomycota (73.23%), Basidiomycota (5.78%), Mortierellomycota (3.41%), and Mucoromycota (0.10%) were the dominant fungal phyla. Our results indicated that soils, plant leaves, and animal feces were the dominant sources of airborne bacterial communities in Hefei City, and the main sources of the fungal communities were plant leaves and soils. The bacterial community was mainly affected by K, Pb, Al, Fe, Mg, Ca, Na+, NO2-, and wind speed, and the main influencing factors of the fungal community were V, Mn, Sr, NO2-, NO3-, Na+, Cl-, the air quality index, and PM10. In addition, nine specific bacteria and fungi that are linked to human health risks were identified, including Acinetobacter, Streptococcus, Enterobacter, Pseudomonas, Delftia, Serratia, Trichoderma, Alternaria, and Aspergillus, which can lead to a wide range of diseases in humans and other organisms. The research results are helpful for revealing the various characteristics of airborne microbial communities, their influencing factors, and their impacts on human health, and are an important reference for subsequent research and the formulation of government policies.

[Fine Particulate Emission Characteristics of an Ultra-Low Emission Coal-Fired Power Plant].

Since the introduction of ultra-low emissions, the characteristics of particulate matter (PM) emissions from coal-fired power plants have changed. We quantitatively evaluate the emission characteristics of each component in PM and the impact of purification equipment by analyzing three ultra-low emission units of coal-fired power plants (FP1, FP2, and FP3). A DGI was used to sample particles from the wet flue gas desulfurization (WFGD) unit and wet electrostatic precipitator (WESP) inlet and outlet, which were then analyzed by various methods. The results showed that the mass concentrations of PM1, PM2.5, and PM10 discharged from the outlets of the three units were 0.25-0.38, 0.31-0.42, and 0.42-0.57 mg·m-3, respectively, and that the mass concentration of PM10 discharged under the two kinds of units was equivalent. However, there were differences in the particle size distribution and composition of the particles. In comparison to the FP1 and FP2 units, the PM2.5/PM10 ratio of the FP3 unit was the highest. A possible reason for this is that the unit was equipped with a WESP, which can better remove particle sizes of 2.5 µm or more. The total concentrations of water-soluble ions in PM2.5 discharged from the FP2 and FP3 units were 0.20 and 0.06 mg·m-3, respectively. The water-soluble ions emitted from the FP2 unit were mainly Ca2+ and SO42-, whereas those mainly emitted from the FP3 unit were NH4+ and SO42-. Analysis of the PM from the WFGD import and export of the FP2 unit showed that the WFGD process increased the water-soluble ion discharge by entraining the desulfurization slurry containing limestone and gypsum. Addition of a WESP after WFGD can effectively remove PM2.5 and PM10 particles and reduce the influence of water-soluble ions on the atmospheric environment.

Molecular dynamics simulation study of the structural characteristics of water molecules confined in functionalized carbon nanotubes.

Molecular dynamics (MD) simulations were performed to study the structural properties of water molecules confined in functionalized carbon nanotubes (CNTs). Four CNTs, two armchair-type (6, 6), (7, 7) and two zigzag-type (10, 0), (12, 0) CNTs, representing different helicities and different diameters, were chosen and functionalized at their open ends by the hydrophilic -COOH and the hydrophobic -CH3 groups. The structural properties of water molecules inside the functionalized CNTs, including the orientation distributions of dipole moment and O-H bonds, the length of the single-file water chain, and the average number of hydrogen bonds, were analyzed during a process of simulations. MD simulation results in this work showed that the -CH3 functional groups exert little special effects on the structural properties of water molecules. It is mainly due to the relatively small size of the -CH3 group and its hydrophobic nature, which is consistent with hydrophobic CNTs. For CNTs functionalized by -COOH groups, the configurations of -COOH groups, incurvature or excurvature, determine whether water molecules can enter the CNTs. The incurvature or excurvature configurations of -COOH groups are the results of synergy effects of the CNTs' helicity and diameter and control the flow direction of water molecules in CNTs.

Helicity and temperature effects on static properties of water molecules confined in modified carbon nanotubes.

Carbon nanotubes show exceptional properties that render them promising candidates as building blocks for nanostructured materials. Many ambitious applications, ranging from molecular detection to membrane separation, require the delivery of fluids, in particular aqueous solutions, through the interior of carbon nanotubes (CNT). To foster such applications, an understanding of the properties of water molecules confined in carbon nanotubes at the molecular level is needed. In this work we report a study of temperature and helicity effects on static properties of water molecules confined in modified CNT by molecular dynamics simulations. It was found that the temperature has little effect on the confined water molecules in carbon nanotubes. But on the other hand, the simulation results showed that because of the difference in helicity between (6, 6) and (10, 0) CNTs, the modification by hydrophilic carboxyl acid functional groups (-COOH) results in a different response to the CNTs, which in turn have control over the flow direction of water molecules in these CNTs.