[Characteristics and Source Apportionment of Volatile Organic Compounds in August in the Chang-Zhu-Tan Urban Area]

Continuous sampling using the tank sampling method were conducted in Changsha, Zhuzhou, and Xiangtan cities from August 18 to 27, 2020, and 106 VOCs species were analyzed using GC-MS analysis. Then, the regional VOCs concentrations, generation potential, and source of VOCs were studied. The results showed that the average φ(VOCs) was (20.5±10.5)×10^-9 in the Changsha-Zhuzhou-Xiangtan area, in which OVOCs (33.5%) and alkanes (28.2%) accounted for the highest proportion. The ozone formation potential (OFP) of VOCs was 118.5 μg·m^-3, and the contributions of aromatic hydrocarbons, olefin, and OVOCs to OFP were 37.4%, 24.2%, and 23.6%, respectively. The average secondary organic aerosol formation potential (SOA_p) of the VOCs was 0.5 μg·m^-3, and the contribution of aromatic hydrocarbons to SOA_p was 97.0%, among which C8 aromatic hydrocarbons contributed 41.7%. Toluene, m/p-xylene, and o-xylene were the common dominant species that contributed significantly to OFP and SOA_p. The characteristic ratio results showed that VOCs in Changsha were relatively influenced by industrial processes and solvent use, whereas Zhuzhou and Xiangtan were more affected by coal and biomass combustion. The PMF results showed that the VOCs mainly came from vehicle exhaust and oil and gas volatilization (27.2%), coal and biomass combustion (23.7%), industrial processes (20.4%), solvent use (17.2%), and natural sources (11.5%) in the Changsha-Zhuzhou-Xiangtan area.

[Characteristics and Source Apportionment of Vehicular VOCs Emissions in a Tunnel Study]

To explore the emission characteristics of volatile organic compounds (VOCs) from vehicular exhaust sources and evaporative sources with ethanol gasoline (E10) as the main fuel, VOCs sampling campaigns were carried out in the north third ring tunnel of Zhengzhou city for two consecutive weeks in December 2019. In addition, the characteristics of traffic flow and environmental information were also monitored in the tunnel. Firstly, 106 VOCs were quantified using gas chromatography/mass spectrometry (GC/MS), and then source apportionment of VOCs in the tunnel was carried out using a positive matrix factorization (PMF5.0)-chemical mass balance (CMB8.2) composite model. Finally, the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of vehicle exhaust sources and evaporative sources were analyzed using the maximum incremental reactivity (MIR) and fractional aerosol coefficient (FAC). The results showed that ρ(VOCs) in the tunnel was (2794.5±147.4) μg·m^-3 during the experiment, among which halogenated hydrocarbons[(32.4±2.0)%] accounted for the highest proportion, followed by aromatic hydrocarbons[(27.5±0.6)%] and alkanes[(23.3±0.8)%]. Source apportionment of vehicular VOCs showed that exhaust emissions (62.5%)>evaporative emissions (37.5%), whereas the contribution of OFP was that exhaust emissions (71.9%)>evaporative emissions (28.1%), and the contribution of SOAFP was that exhaust emissions (75.8%)>evaporative emissions (24.2%). The dominant components of OFP in evaporative sources were m,p-diethylbenzene, isoprene, and trans-2-pentene, whereas m,p-diethylbenzene, m,p-xylene, and 1,2,3-trimethylbenzene were the dominant components of SOAFP. The major components of OFP in exhaust sources were m,p-xylene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene, whereas m,p-xylene, m,p-diethylbenzene, and 1,3,5-trimethylbenzene were the dominant components of SOAFP. In regions where ethanol gasoline is used, special attention should be paid not only to the exhaust emissions control but also to strengthening the emissions reduction of VOCs from vehicle evaporative sources, especially the high active components such as aromatic hydrocarbons and alkenes.

[Characteristics and Source Apportionment of VOCs at Different Pollution Levels During the Winter in an Urban Area in Zhengzhou]

In this study, volatile organic compound (VOC) species were measured at an urban site in Zhengzhou from January 3 to 23, 2019, to investigate the composition, variation characteristics, sources, and effects on secondary organic aerosol (SOA) formation of VOCs at different pollution levels. Results showed that oxygenated VOCs and alkanes were the main components of VOCs, while ethyl acetate and acetone were the most abundant species. During the process from clean days to heavy pollution days, the mixing ratio of VOCs approximately doubled, and the mixing ratios of most species continued to increase as the pollution level increased. Based on the positive matrix factorization (PMF) model, during the observation period, VOCs mainly originated from vehicle emissions, industrial emissions, combustion sources, solvent utilization, and liquefied petroleum gas (LPG) utilization. There were significant differences in the source contribution at different pollution levels, and the contributions of industrial emissions and solvent utilization during the heavy pollution days increased to 9 times and 3 times that of the clean days, respectively. With respect to the SOA formation potential (SOA_p), aromatics were the component that contributed the most, and toluene and m/p-xylene were the species that contributed the most, while solvent utilization was the greatest source contributor. During the heavy pollution period, the total SOA_p increased to approximately 2.6 times that of clean days. There is a great need to reduce winter haze pollution in Zhengzhou by strengthening the control of aromatic emissions and related sources such as solvent utilization.

[Characteristics and Source Apportionment of Ambient Volatile Organic Compounds in Winter in Jincheng]

Air samples were collected and analyzed by GC-MS to investigate the component characteristics of volatile organic compounds (VOCs) in winter in Jincheng. PMF, ratio analysis, and the backward trajectory model were used to investigate sources of VOCs. Ozone formation potential and secondary organic aerosol formation potential were calculated, in order to analyze the environmental implications of detected VOCs. Results showed that the average concentration of VOCs was 93.35 μg·m^-3 in Jincheng, with the most abundant component being alkane (52.91 μg·m^-3 and 56.68% of total VOCs). Based on PMF analysis, five sources of ambient VOCs in Jincheng were identified, namely industrial emission sources (33.71%), fuel combustion sources (30.27%), vehicle emissions (26.28%), solvent evaporation sources (9.00%), and plant emission sources (0.74%). Ratios of B/T and i-pentane/n-pentane were 1.58±0.68 and 2.07±0.43, indicating that VOCs were derived from the mixture of road and coal combustion sources. Clustered analysis of the air mass backward trajectory showed that three air masses cluster, which were accounting for 50%, 25% and 25% of the total back trajectories respectively, all came from the northwest, and industrial pollution from the northwest might therefore significantly influence VOCs in Jincheng. With low wind speed (<3 m·s^-1), the air quality index, concentration of total VOCs, and contribution rate of vehicle emissions were 143, 162.48 μg·m^-3, and 46.16%, respectively, higher than values at faster wind speeds (3-6.9 m·s^-1). Ozone formation potential and secondary organic aerosol formation potential of aromatic hydrocarbons, which had the highest formation potential, were 98.89 μg·m^-3 and 1.21 μg·m^-3, respectively, accounting for 37.28% and 97.01% of total formation potential. To reduce the pollution of VOCs in Jincheng, it is important to control industrial emissions, vehicle emissions, and fuel combustion emissions.