[Seasonal Chemical Composition Characteristics and Source Apportionment of PM2.5 in Zhengzhou].

The aim of this study was to fully understand the pollution characteristics and sources of PM2.5 in Zhengzhou, and to investigate the differences in four seasons and between urban and suburban areas. At the Zhengzhou environmental monitoring center (urban areas) and Zhengzhou University (suburban areas), 1284 environmental PM2.5 samples were collected in the four seasons of 2018. The concentrations of nine kinds of inorganic water-soluble ions, organic carbon, elemental carbon and 27 kinds of elements, were measured by ion chromatography, carbon analyzer, and X-ray fluorescence spectrometry, respectively. Enrichment factors (EF), index of geoaccumulation (Igeo), potential ecological risk index (RI), chemical mass balance model (CMB), backward trajectory, and potential source contribution function were the methods used to study the chemical component characteristics and source differences of PM2.5 in different seasons in the urban and suburban areas of Zhengzhou. The results showed that the annual average PM2.5 concentration at the Zhengzhou environmental monitoring center and Zhengzhou University sites reached (59.7±24.0) µg·m-3 and (74.7±13.5) µg·m-3, respectively. The PM2.5 concentration at the suburban point was higher than at the urban point with the exception of winter, and the seasonal mean concentration decreased in the order of winter > autumn > spring > summer. Compared with the urban areas, the suburban areas were more affected by crustal substances in spring, and the concentrations of all components were higher in summer and autumn than the urban areas. Nevertheless, urban areas were more affected by coal burning sources and motor vehicle sources in winter. The component analysis results showed that the influences of soil dust and building dust were greater in the suburbs in spring than in the urban areas. In autumn, the suburbs were more affected by biomass sources than the urban areas, while the urban areas were more affected by building dust than were the suburbs. The concentrations of Cu, As, Zn, Pb, and Sb were strongly influenced by anthropogenic sources, and the enrichments of Zn, Cu, As, and Pb in urban areas were greater than in the suburbs. In addition, Zn, Cu, As, and Pb exhibited potential ecological risks. The outcomes of the CMB model showed that dust sources, secondary sulfate, secondary nitrate, and coal burning sources contributed significantly to PM2.5 concentrations in spring, summer, autumn and winter, respectively. The contributions of secondary pollution sources (secondary organic aerosol, secondary sulfate, and secondary nitrate) and motor vehicle sources to urban areas were higher than to suburban areas, and the influences of biomass sources in autumn and winter were significantly higher than in spring and summer and urban areas. The backward trajectory results indicated that the local PM2.5 concentration was affected by distant transmission from the northwest except in summer, was affected by neighboring provinces in the east in four seasons, and was affected by transmission from the south, with the exception of winter. Furthermore, the consequences of potential sources demonstrated that the local PM2.5 concentration was mainly affected by the potential areas in Henan province and its boundary with neighboring provinces.

[Seasonal Characteristics and Source Analysis of Water-Soluble Ions in PM2.5 of Anyang City].

We explore the characteristics and sources of water-soluble ions in aerosol fine particulate matter (PM2.5) samples collected from Anyang, China, during typical seasonal months from 2018 to 2019. Nine water-soluble ions (Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, and SO42-) were analyzed. The analysis of PM2.5, water-soluble ion concentration levels, anion-cation balance, nitrogen oxidation rate (NOR), sulfur oxidation rate (SOR), and ion correlation showed that the annual average concentrations of PM2.5 and water-soluble ions in Anyang were (85.81±45.43) µg·m-3 and (48.21±30.04) µg·m-3, respectively. Concentrations of ions were ranked as:NO3- > SO42- > NH4+ > Cl- > K+ > Ca2+ > Na+ > Mg2+ > F-. The annual average concentration of the sum of NH4+, NO3-, and SO42- was (42.72±27.87) µg·m-3, which accounted for 87.14% of total water-soluble ions. Moreover, NH4+ was highly related to SO42- and NO3-. The mean values of the nitrogen oxidation rate (NOR) and sulfur oxidation rate (SOR) were 0.25 and 0.37, respectively. These results suggest that these ions were the result of secondary formation. The anion-cation charge equivalent value was 0.75-0.94, which indicates that the sampled aerosols were alkaline. NH4+ mainly existed in the form of (NH4)2SO4 and NH4NO3 in spring, summer, and autumn, whereas in winter it mainly existed in the form of NH4Cl. The results of principal component analysis indicated that secondary aerosols, coal combustion, biomass burning, and dust were the main sources of the water-soluble ions in Anyang during the sampled periods.

[Analysis of Air Pollution Characteristics and Meteorological Conditions in Zhengzhou from 2014 to 2017].

Online monitoring data of atmospheric pollutants and meteorological parameters in Zhengzhou from 2014 to 2017 were collected to analyze the concentration levels, seasonal variations, and the ratio characteristics of atmospheric pollutants, as well as the effects of meteorological conditions on these pollutants. Results show that the annual average concentrations of PM2.5 and PM10 in the four years were (88±49.8), (95.8±60.2), (78.6±70.3), and (72.0±53.5) µg·m-3, and (158.5±65.3), (167.7±82.6), (144.5±91.5), and (132.7±70.3) µg·m-3, respectively, and were approximately two times higher than the grade Ⅱ annual limits set by China. Fuel combustion and the formation of secondary pollutants were the main sources of PM2.5 in Zhengzhou. Moreover, the contribution of coal combustion was found to be decreased, while that of traffic sources increased year by year. Low wind speed, high humidity, and reduced precipitation are important meteorological factors that contribute to serious air pollution. In addition, the Potential Source Contribution Function and the Concentration-Weighted Trajectory were used to analyze the potential sources, and the contribution of these sources to the distribution of PM2.5. The potential source areas of PM2.5 were mainly distributed in neighboring cities and provinces, such as Shanxi, Shaanxi, Hubei, Shandong, and Hebei. The short-distance transmission was found to contribute significantly to the mass concentration of PM2.5.

[Transport Pathways and Potential Sources of PM2.5 During the Winter in Zhengzhou].

In this study, meteorological and air mass concentration data of Zhengzhou from December 2017 to February 2018 (winter) were used to quantify the influence of meteorological factors on the PM. The Hybrid Single-Particle Lagrangian Integrated Trajectory model was used to analyze the 48-hour backward trajectories and the cluster method was applied to classify the airflow backward trajectory. Moreover, the potential source contribution function and concentration-weighted trajectory analysis were applied to evaluate the transport pathways and sources of PM2.5 in Zhengzhou. The results show that the heavy pollution in Zhengzhou during winter is mainly due to the low wind speed, high relative humidity, and low precipitation. The cluster analysis revealed that up to 60% of the back trajectories came from the northwest and 25.56% of the back trajectories came from the Beijing-Tianjin area. The airflow trajectories from the south and east account for 7.5% and 6.1% with higher PM2.5 concentrations. The main potential sources of PM2.5 in Zhengzhou during winter are located in Beijing-Tianjin-Hebei air pollution transmission channel cities including Jiaozuo, Kaifeng, Xinxiang, Hebi, Puyang, Anyang, Handan, and Xingtai. The adjacent provinces, including Shanxi, Hubei, and Anhui, also have great influence on the PM2.5 in Zhengzhou.