[Chemical Composition and Source Analysis of PM2.5 in Yuncheng, Shanxi Province in Autumn and Winter].

In order to reveal the chemical composition characteristics and pollution sources of fine particulate matter (PM2.5) in autumn and winter in Yuncheng, PM2.5 samples were continuously collected using a four-channel small-flow particulate sampler from October 15, 2018 to March 15, 2019. The study prediminantly analyzed the chemical components of water-soluble ions, elemental carbon, organic carbon, and metal elements. Additionally, the chemical mass reconstruction method of particulate matter and the positive matrix factorization model (PMF) were combined for an in-depth discussion. During the sample period, the PM2.5 mass concentrations range was 29.37-370.11 µg·m-3, and 101 days during the sampling period exhibited concentrations that were higher than the secondary standard in China's Ambient Air Quality Standards (GB 3095-2012), with an exceeding rate of 70.63%. These results indicate that the air pollution in Yuncheng in autumn and winter is serious. According to the air quality index (AQI), the collected samples are classified as clean, light-moderate pollution, and heavy-severe pollution. Water-soluble ions, OC, EC and metal elements account for 40%, 19%, 5%, and 7% on clean days, 46%, 18%, 4%, and 5% on days with light-moderate pollution, and 46%, 21%, 4%, and 4% on days with heavy-severe pollution, respectively. Secondary ions NO3-, SO42-, and NH4+ are the primary components of water-soluble ions, accounting for 81% (clean days), 87% (light-moderate pollution), and 87% (heavy-severe pollution) of the total ion concentration, respectively. The OC/EC ratios during the sampling period were 3.78 (clean days), 4.02 (light-moderate pollution), and 5.37 (heavy-severe pollution). With the intensification of pollution, the pollution of secondary organic aerosols in the atmosphere becomes increasingly serious. In addition, as the air pollution increased, the concentration of Fe and Cr elements gradually decreased, while the concentration of other metal elements showed an overall upward trend. The results of the chemical mass reconstruction demonstrate that among the different pollution levels of atmospheric PM2.5 in Yuncheng, the mass percentages of secondary inorganic salt, sea salt, heavy metals, mineral dust, construction dust, organic matter, and elemental carbon were 36%, 2%, 2%, 8%, 1%, 33%, and 5% (clean days), 41%, 1%, 1%, 5%, 0.01%, 31%, and 5% (light-moderate pollution), and 41%, 1%, 1%, 4%, 0.004%, 34%, and 4% (heavy-severe pollution). The proportion of secondary inorganic ions increased and mineral dust decreased with the deterioration of air quality. The PMF analysis results suggest that secondary related sources, coal combustion sources, vehicle exhaust sources, biomass burning, and secondary organic matter are the predominant sources of PM2.5 during serious air pollution in Yuncheng.

[Pollution Characteristics and Source Analysis of Aromatic Compounds in Shijiazhuang].

To understand the pollution characteristics of aromatic compounds in Shijiazhuang, PM2.5 samples were collected day and night for 30 days from September 18 to October 17, 2016. Qualitative and quantitative analyses were conducted using gas chromatography-mass spectrometry (GC-MS). The results showed that total average concentration of aromatic compounds was 33.5 ng·m-3, lower than that of levoglucosan (487 ng·m-3). Concentration of nitro-aromatic compounds was the highest (20.4 ng·m-3), followed by aromatic acids (9.94 ng·m-3) and aromatic aldehydes (3.14 ng·m-3). Influenced by the decrease in the boundary layer and temperature, concentration of 8 substances during night was higher than during the day. There was a significant positive correlation between levoglucosan and nitro-aromatic, aromatic aldehyde, and aromatic acid compounds, with correlation coefficients (r) of 0.6829, 0.6443, and 0.6782, respectively, indicating that biomass burning is an important primary source of aromatic compounds that directly affects their concentrations in the atmosphere. Based on the analysis of daily variation trends in total concentration of aromatic compounds and the backward trajectory model, it was found that the pollution of aromatic compounds in Shijiazhuang in autumn was affected by regional transportation and local emissions.

[Concentration and Ecological Risk Assessment of Heavy Metals in PM2.5 Collected in Urban and Suburban Areas of Beijing].

Atmospheric PM2.5 pollution and ambient air quality were investigated in Beijing, and the ecological risks of the trace heavy metals in PM2.5 were analyzed. PM2.5 samples were collected from Dongzhimen and Huairou by a middle volume sampler, and 16 kinds of trace metals were determined by inductively couple plasma-mass spectrometry (ICP-MS). The results showed that the average concentration of PM2.5 in the urban area was 92.35 µg·m-3, and the number of days higher than the Ambient Air Quality Standards (GB 3095-2012) accounted for 41.7% of the total number of days. The average concentration of PM2.5 in the suburban area was 70.90 µg·m-3, and the standard exceedance rate was 31.7%. In general, the spatial and temporal distributions of heavy metals were as follows:nighttime > daytime; urban area > suburban area; winter > autumn > spring > summer. The enrichment factors for Pb, As, Zn, Ni, and Cu in the urban area and Pb, As, Zn, Cr, Ni, and Cu in the suburban area indicated that most came from anthropogenic sources. The result for the geoaccumulation index indicated that Ni is affected by anthropogenic sources and natural resources, while Cu, Zn, As, Cd, and Pb might have been derived from human activities. The potential ecological risk of Cu, Zn, Pb, and Cd was high, while the degree of ecological harm posed by Cd was extremely strong.

[Analysis of Different Particle Sizes, Pollution Characteristics, and Sources of Atmospheric Aerosols During the Spring Dust Period in Beijing].

To understand the evolution of the physical and chemical properties of dust aerosols in the atmosphere, the concentrations and chemical compositions of differently sized particles were continuously observed and analyzed using an ion chromatograph and carbonaceous analyzer during the outbreak of dust in May 2017 in Beijing. The concentrations of total suspended particulate (TSP), water-soluble organic carbon (WSOC), elemental carbon (EC), OC, and water-soluble inorganic ions were (2237.59±681.49), (29.90±18.05), (1.46±3.05), (67.35±29.07), and (136.75±46.38) µg·m-3 during the dust period, respectively, and significantly exceeded that of the non-dust period, except for EC. The Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3-, SO42-, and WSOC concentrations during the dust storm period were 11.55, 3.00, 14.88, 14.89, 9.40, 4.60, 2.40, 3.91, and 1.83 times higher than that during the non-dust period. The growth of crustal ions, such as Ca2+ and K+, was notably the largest and NH4+ and NO3- were minimal. The size distribution indicates that crustal ions primarily occur in the coarse mode during the whole sampling campaign. The SO42- and NO3- ions are slightly bimodal during the dust storm, with a dominant peak in the coarse mode at 4.7-5.8 µm and a very minor peak in the fine mode with a size range of 0.43-0.65 µm. During the non-dust period, SO42- is the dominant mode in the fine mode, while NO3- changes little compared with that during the dust period, which indicates that heterogeneous reaction with crustal ions is the main formation mechanism of NO3- in the coarse mode. A significant positive correlation was observed between SO42- and the sum of crustal ions during the dust period, indicating that the source of SO42- during the dust period is remote transmission of the dust storm. During the non-dust period, the positive correlation of SO42- with NH4+ indicates that secondary formation is the main source of SO42-. Based on correlation analysis of NO3- with crustal ions and NH4+, both remote transmission and secondary formation are the sources of NO3- during the dust storm and heterogeneous reactions are predominant during the non-dust period.