[Chemical Compositions and Sources of n-Alkanes and Saccharides in PM2.5 from Taian City During the Summer].

To investigate the variations and sources of n-alkanes and sugars in Taian City during summer, PM2.5 samples were collected from July 22 to August 19, 2016. The identified n-alkane and sugar sources were investigated using a principal component analysis (PCA) multiple linear regression (MLR) model and a backward trajectory model. The results showed that the mass concentrations of PM2.5 during summer were (37.2±11.5) µg·m-3. The mass concentrations of n-alkanes were (83.3±34.7) ng·m-3, the carbon preference index (CPI) was 1.83, and the relative contribution of wax n-alkanes was 34.7%-69.4%, suggesting that contributions from terrestrial plants were more significant in Taian City. The results showed that the mass concentrations of sugars in Taian City during summer were (73.4±46.6) ng·m-3. Levoglucan, galactosan, and mannosan were the main saccharides, accounting for 64.0%, 7.1%, and 6.3% of the total concentrations of sugars, respectively, indicating that biomass burning is much more significant in Taian City. The results of the PCA-MLR model suggested that n-alkanes and sugars in Taian City during summer were mostly from terrestrial plants, coal burning and biomass burning. The backward trajectory model showed that the pollution mostly came from the native sources of Shandong province and the inland cities in the south.

[Diurnal Variations and Source Analysis of Water-soluble Compounds in PM2.5 During the Winter in Liaocheng City].

To investigate the diurnal variations and sources of water-soluble compounds in Liaocheng City, PM2.5 samples were collected between January and February 2017. The PM2.5 samples were analyzed for the compositions, concentrations, and sources of water-soluble inorganic ions, oxalic acid, and levoglucosan. The sources of these chemical compound were investigated using principal component analysis (PCA) and multiple linear regression (MLR) modeling. The results showed that the mass concentrations of PM2.5during the nighttime were higher than those during the daytime, and the average concentrations exceeded the National Ambient Air Quality Standard (GB 3095-2012) by more than 1.8 times. Moreover, atmospheric pollution was worse during the day than during the night. SNA (SO42-, NO3-, and NH4+) were the dominant species among the inorganic ions, the relative abundance of which with respect to the total concentrations of inorganic ions was 73.4% and 77.1% during the daytime and nighttime, respectively. The ratios of anion to cation equivalents (AE/CE) were less than one, suggesting that the PM2.5 was slightly alkaline, and the degree of acidity at night was stronger than during the day. The results of the correlation analyses suggested that aqueous-phase oxidation was the major formation pathway of oxalic acid, which is driven by acid-catalyzed oxidation. The oxalic acid was mainly influenced by biomass burning during the winter in Liaocheng City. The results of the PCA-MLR model suggested that water-soluble compounds in Liaocheng City were mostly from vehicular emissions and secondary oxidation, biomass burning, while the impacts of mineral dust and coal burning were relatively minor.

[Source Analysis and Health Risk Assessment of PAHs in PM2.5 During Winter in Liaocheng City].

To investigate the mass concentrations, sources, and health effects of polycyclic aromatic hydrocarbons (PAHs) in ambient particulate matter (PM) in Liaocheng City during winter, 14 types of PAHs in PM2.5 were determined from January to February of 2017. The sources of the PAHs were analyzed by using diagnostics ratios and the principal component analysis (PCA)-multiple linear regression (MLR) model,and the health risk of PAHs was assessed by BaP equivalent concentrations (BaPeq) and incremental lifetime cancer risk (ILCR). The results showed that the mass concentrations of PAHs in PM2.5 during winter were (64.89±48.23) ng·m-3, Fla, Pyr, and Chry were predominant species, accounting for 15.5%, 12.8%, and 12.7% of the total concentrations of PAHs, respectively. Moreover, the ring distribution of the PAHs was dominated by four-ring PAHs. The pollution during the pre-Spring Festival and firework Ⅱwere the most severe during the sampling period. The results of the PCA-MLR model suggested that PAHs originated mostly from coal burning, biomass burning, and vehicle emissions. The toxicity exposure index (TEQ) in Liaocheng City during winter was (6.37±4.92) ng·m-3. The results of the risk model revealed that the ILCR of adults was higher than that of children, and both groups of ILCR for winter were in the range of the risk threshold. This suggests that a potential risk in terms of inhalation PAH exposure for residents in Liaocheng City.

[Pollution Characteristics and Source Analysis of n-alkanes and Saccharides in PM2.5 During the Winter in Liaocheng City].

To investigate molecular composition, mass concentrations, and sources of n-alkanes and sugars which are adsorbed in ambient particulate matters in Liaocheng City during winter, PM2.5 samples were collected from January 17 to February 15, 2017 at Liaocheng University. 19 kinds (C18-C36) of n-alkanes and 10 kinds of sugars were determined using GC-MS. The identification of n-alkane and sugar sources were investigated using principal component analysis (PCA). The results showed that the mass concentrations of total n-alkanes in PM2.5 during the winter were (456.9±252.5) ng·m-3. During the haze period, the concentrations of n-alkanes were two times higher than those on clear days. Additionally, the concentrations of n-alkanes during fireworks event I and fireworks event Ⅱ were 0.9 times and 1.2 times higher than those on clear days. During the sampling period, the Carbon preference index (CPI) was 1.2±0.1, and the contribution from plant wax concentrations for n-alkanes (% Wax Cn) was between 3.1%~36.0%, indicating that fossil fuels were the major source of n-alkanes in Liaocheng City during the winter. The mass concentrations of saccharides in PM2.5 during the winter were (415.5±213.8) ng·m-3. Levoglucosan was the most abundant species, followed by galactosan and mannosan, which accounted for more than 91.6% of total saccharides, indicating that biomass burning was much more significant in Liaocheng City. PCA further suggested that n-alkane and saccharide compounds in atmospheric aerosol during the winter in Liaocheng City were primarily derived from fossil fuel and biomass burning.

[Analysis of Seasonal Variations in Chemical Characteristics and Sources of PM2.5 During Summer and Winter in Ji'nan City].

To investigate seasonal variations in the chemical compositions of aerosols in Ji'nan City, PM2.5 samples were collected during summer and winter in 2015. The sampling period lasted one month during each season. PM2.5 samples were analyzed for the composition, concentration, and sources of water-soluble inorganic ions, organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC). Results showed that mass concentrations of PM2.5 in winter were about twice those in summer, and concentration levels varied between fine and excellent. The concentrations of total water-soluble inorganic ions were also higher in winter than in summer, with SO42-, NO3-, and NH4+ being the dominant species and well correlated with each other. NH4+ in PM2.5 mostly existed in the form of (NH4)2SO4 and NH4NO3 in both summer and winter. There was strong secondary oxidation of SO2 and NO2. The sulfate oxidizing rate (SOR) was higher in summer than in winter, while the nitrate oxidizing rate (NOR) showed the opposite trend. The ratio of anions to cations in both summer and winter were less than one, suggesting that PM2.5 were slightly alkaline. The ISORROPIA-Ⅱ mode showed that acidity in winter was stronger than in summer. Concentations of OC and EC were both higher in winter than in summer. The ratios of OC to EC and WSOC to OC and estimated concentrations of secondary organic carbon (SOC) showed that secondary pollution was more serious in winter than in summer. Principal component analysis(PCA)indicated that the major sources contributing to inorganic ions were secondary oxidation and biomass burning in summer, and coal combustion and secondary pollutants formed by chemical oxidation of precursors emitted from coal combustion in winter.

[Diurnal Variation of Dicarboxylic Acids and Related SOA in PM2.5 from Heze City in Winter].

To identify the diurnal variation and formation mechanism of dicarboxylic acids and related compounds in PM2.5 from Heze City, PM2.5 samples were collected in the winter (December) of 2017, which were subsequently analyzed for dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, and levoglucosan (Levo). The results showed that the total concentrations of dicarboxylic and ketocarboxylic acids were higher during daytime than those during nighttime. In contrast to the diurnal variation of dicarboxylic and ketocarboxylic acids, the total concentrations of α-dicarbonyls exhibited higher concentrations in nighttime than in daytime. Because α-dicarbonyls are the major precursors of dicarboxylic acids, the opposing patterns suggest that the photochemical oxidation in daytime is stronger than that in nighttime. Oxalic acid (C2) is the dominant species during both day-and nighttime, followed by phahalic acid (Ph), succinic acid (C4), and malonic acid (C3), which is consistent with that in other urban regions. The mass ratios of C3/C4 (R2>0.7) correlated strongly with temperature, indicating that organic compounds in the atmosphere of Heze City are mainly derived from the photochemical oxidation of local emissions rather than long-range transport in winter. C2 correlated with in-situ pH and SO42-, suggesting that aqueous-phase oxidation was the major formation pathway of C2, which is driven by acid-catalyzed oxidation. Since the major SOA (C2, glyoxal, and methyglyoxal, secondary organic aerosol) correlated with Levo and the average mass rations of K+/organic carbon was 0.06 (ranging from 0.03 to 0.13), it can be concluded that the dicarboxylic acids and related SOA and K+ in Heze City were significantly influenced by biomass burning in winter.