[Analysis of Photochemical Characteristics and Sensitivity of Atmospheric Ozone in Nanjing in Summer]

Tropospheric ozone (O3) is mainly produced through a series of photochemical reactions of nitrogen oxides (NOx) and volatile organic compounds (VOCs). The reaction process presents complex non-linear relationships. In this work, datasets of atmospheric ozone and volatile organic compounds (VOCs) observed during the summer of 2018 in Nanjing were used. Combining with the framework for 0-D atmospheric model-master chemical mechanism (F0AM-MCM), the characteristics of photochemical reactions for ozone (O3) formation in Nanjing during the O3 episode days and non-episode days were investigated. The results showed that φ(O3) and φ(TVOCs) in the O3 episode days were 47.8×10-9 and 49.0×10-9, respectively, exceeding those in the non-episode days by factors of 1.8 and 1.6. Furthermore, F0AM, the empirical kinetic modeling approach (EKMA), and relative incremental reactivity (RIR) were utilized for the calculation of ozone chemical sensitivity. It was found that O3 formation in Nanjing was attributed to both VOCs and NOx limitation. In addition, the modeled ·OH and HO2 concentrations in the O3 episode days were 1.3 and 1.8 times higher than those in the non-episode days. The higher formation and loss rates of ·OH and HO2 were also found during O3 episode days. These findings reflected that the enhancements of atmospheric oxidation capacity resulted in increased production rates of O3, providing an explanation for the enhancements of O3 concentrations in Nanjing during the O3 episode days. The findings also improved the understanding of the O3 photochemical characteristics over Nanjing in the summer during the O3 episode days.

[Emission Trends and Reduction Potential of VOCs from Printing Industry in China]

The printing industry has always been the key source of volatile organic compound(VOC) emissions in China. However, owing to the complexity of raw materials and processes, the fine emission inventory and its future emission reduction potential of VOCs from the printing industry have not been well characterized. In this study, the existing VOCs emission factors of the printing industry were improved, considering the neglected semi/intermediate VOCs(S/IVOCs). An emissions inventory of VOCs from the printing industry in the period of 2011-2020 in China was compiled. Through scenario analysis, the emission of VOCs under different scenarios in 2030 was predicted, and the emission reduction potential was analyzed. VOCs emissions from the printing industry in China increased first and then decreased in the period of 2011-2020. Compared with that in 2011, VOCs emissions increased by 29.6% in 2020, with an average annual growth rate of 3.0%. This was mainly due to the increasing consumption demand in the printing industry market and the lack of effective measures for integrated management of VOCs. The VOCs emission of the printing industry in China in 2020 was 861 Gg. Gravure printing and packaging processing were the two most important processes, accounting for 52.0% and 28.7%, respectively. Guangdong, Jiangsu, and Zhejiang were the largest contributors to VOC emissions, accounting for 44.12% of the total emissions. VOCs emissions of the printing industry in 2030 were 1187 Gg, 684 Gg, and 362 Gg for the baseline scenario, the general control scenario, and the strict control scenario, respectively. Compared to that in 2020, emissions under different control scenarios in 2030 increased by 37.9% and decreased by 20.6% and 57.9%, respectively. Gravure printing and packaging processing are still the focus of emission reduction.

[Pollution Characteristics and Source Apportionment of Volatile Organic Compounds in Lishui Area of Nanjing]

To understand the changes in the components of volatile organic compounds(VOCs), the contribution proportion of each component to ozone, and the VOCs sources, we monitored the VOCs for a year in Lishui. The results showed that theρ(TVOC) was 223.46 μg·m-3, ρ(alkanes) was 49.45 μg·m-3(22.3%), ρ(OVOCs) was 50.63 μg·m-3(22.66%), ρ(halogenated hydrocarbons) was 64.73 μg·m-3(28.95%), ρ(aromatic hydrocarbons) was 35.46 μg·m-3(15.87%), ρ(alkenes) was 18.26 μg·m-3(8.19%), and ρ(others) was 4.9 μg·m-3(2.2%). ρ(TVOC) was higher in summer(263.75 μg·m-3) and lower in winter(187.2 μg·m-3), with 246.11 μg·m-3 in spring and 204.77 μg·m-3 in autumn. The daily concentration of VOCs showed two peaks, one from 9:00 to 10:00 and another from 14:00 to 15:00, and the high concentration was mainly found in the urban main road area with dense human activities. The ozone formation potential(OFP) was 278.92 μg·m-3, and those of olefin and aromatic hydrocarbon were 114.47 μg·m-3(41.1%) and 113.49 μg·m-3(40.8%), respectively, contributing over 80%, which was an important precursor of ozone. On the other hand, the ratio of characteristic compounds to toluene/benzene(T/B) was 4.13, which indicated that it was greatly affected by the solvent usage. In the end, the results of positive matrix factorization(PMF) source apportionment showed that VOCs mainly came from solvent usage, industrial production, and traffic emissions. The VOCs pollution had a great influence on ozone, so it was necessary to strengthen the treatment of industrial production, solvent usages, and traffic emissions.

[Effects of Source Depletion on Vapor Intrusion Risk Assessment]

The current regulatory site investigation employs the J&E model to predict vapor intrusion risk. However, the J&E model assumes that the source concentration is constant for a given exposure period, which is not consistent with the actual site source under depletion. In this study, we compared the differences between the J&E model (constant source), SD source depletion model, and RBCA source depletion model for predicting indoor concentration variation as well as the risk levels during the exposure period with a case study in Beijing. The results showed that the source and indoor air concentrations predicted by the SD and RBCA models showed exponential decreases, whereas those predicted by the J&E model maintained high concentrations throughout the exposure period, which greatly overestimated the risk. The RBCA predicted source depletion at the fastest rate, but the predicted indoor air concentrations were still lower than those of the SD model, which was related to the fact that the RBCA did not consider the effect of buildings on source depletion and did not follow mass conservation. Further, the sensitivity analysis showed that the pressure difference (dP) had the greatest influence on the source concentration in the SD model. For the calculated carcinogenic risk and hazard quotients, the J&E constant source model, the SD source depletion model, and the RBCA source depletion model were ranked in descending order. The results indicated that in general the J&E model was too conservative, the RBCA model may have underestimated risk, and the SD model was more suitable for quantifying vapor intrusion risk in reality.

[Sensitivity Analysis of Ozone Formation Using Response Surface Methodology]

Identifying the nonlinear relationship between O₃ and its precursors accurately plays an important role for the policy-making of O₃ pollution control. In this study, the response surface methodology based on the box model simulation was used to quickly and efficiently quantify the O₃ response to their precursors with the optimal experimental design. The results showed that CO had a positive contribution to ozone generation, whereas NO_x and VOCs had a significant nonlinear relationship with O₃. When the ratio of φ(VOCs) to[φ(NO_x)-13.75] was greater than 4.17, the ozone formation regime was NO_x-limited and became VOCs-limited when the ratio was less than 4.17. Olefin was the key VOCs' component to affect the formation of O₃; when the radio of φ(olefin) to[φ(NO_x)-15] was less than 1.10 and the value of the φ(olefin) was less than 35×10^-9, olefin went far towards generating O₃. Response surface methodology demonstrated that it can be well used to explore the influence of multiple factors and their interactions on O₃ formation and provides a new approach for efficient O₃ sensitivity analysis.

[Characteristics and Source Apportionment of Volatile Organic Compounds in Zhanjiang in Summer]

Ozone pollution is intensifying in China, and its related studies are weak in non-focus regions and non-focus cities. Here, we investigated the characteristics and sources of volatile organic compounds (VOCs) at three sampling sites in Zhanjiang. We analyzed 101 VOCs using a gas chromatography-mass spectrometry/hydrogen ion flame detector (GC-MS/FID) and high-performance liquid chromatography (HPLC) using a Summa canister and DNPH adsorption tube. We calculated the ozone formation potential (OFP) of VOCs and used the positive matrix factorization (PMF) model for source apportionment. The results showed that the mean φ(TVOCs) was 1.28×10^-7, and the dominant contributors were OVOCs (52%), followed by alkanes (36%), alkenes (7%), halogenated hydrocarbons (2.42%), aromatic hydrocarbons (1.61%), and alkynes (0.78%). The diurnal variation in VOCs was influenced by photochemical reactions; the ratio of aromatic hydrocarbons and alkanes was high in the morning and evening and low at noon, whereas OVOCs had a low ratio in the morning and noon and high in the evening, influenced by primary emissions and the upwind transport of pollutants. The OFP was 3.28×10^-7, and the dominant species were formaldehyde, butene, n-butane, butanone, and acetaldehyde.The analysis of X/E values (characterizing the aging degree of air masses) and backward trajectories of air masses showed that during the sampling, when influenced by air masses from the south or southwest, X/E was small, and the aging degree of air masses was high, indicating the influence of regional transport; when influenced by air masses from the east or southeast direction, X/E was large, and the air masses were fresh, and VOCs were mainly from local emissions. Six emission sources of VOCs, including industrial emissions, gasoline vehicle exhaust and gasoline evaporation, regional background and transport sources, biomass combustion, diesel vehicles and marine shipping emissions, and solvent use emission sources, were resolved using the PMF model, with contributions of 36.05%, 28.99%, 13.84%, 10.13%, 7.05%, and 3.95%, respectively.Zhanjiang should strengthen the supervision of formaldehyde, butene, n-butane and butanone, industry sources, and mobile sources as the focus of control.

[Variation Characteristics and Ozone Formation Potential of Ambient VOCs in Urban Beijing in Summer]

To further understand the effect of volatile organic compounds (VOCs) on ozone (O₃) formation in seasons when ozone (O₃) pollution occurs frequently, the variation in VOCs, chemical composition characteristics, and ozone formation potential (OFP) were studied, using high-resolution online monitoring data obtained in an urban site of Beijing in the summer of 2019. The results showed that the averaged total mixing ratio of VOCs was (25.12±10.11)×10^-9, with alkanes as the most abundant group (40.41%), followed by oxygenated volatile organic compounds (OVOCs) (25.28%) and alkenes/alkynes (12.90%). The diurnal variation in VOCs concentration showed a bimodal pattern with the morning peak appearing from 06:00 to 08:00, when the proportion of alkenes/alkynes increased significantly,indicating that the vehicle exhaust contributed more to VOCs. The VOCs concentration decreased in the afternoon when the proportion of OVOCs showed an upward trend, and the photochemical reaction and meteorological factors had great influences on VOCs concentration and composition.The OFP in urban Beijing in summer was 154.64 μg·m^-3; aromatics, OVOCs, and alkenes/alkynes played dominant roles in OFP; and hexanal, ethylene, and m/p-xylene were the key species. The results suggested the need for the control of vehicle and solvent use and restaurants emissions to reduce the high level of O₃in urban Beijing in summer. The diurnal variations in ethane/acetylene (E/E) and m/p-xylene/ethylbenzene (X/E) showed that the photochemical-aging of the air masses was obvious, which was jointly affected by photochemical reactions and regional transport. The back-trajectory results indicated a high contribution of southeastern and southwestern air masses to atmospheric alkanes and OVOCs concentration; moreover, aromatics and alkenes were mainly from local sources.

[Chemical Characteristics and Source Apportionment for VOCs During the Ozone Pollution Episodes and Non-ozone Pollution Periods in Qingdao]

The ambient concentration of ozone is high in Qingdao, and ozone pollution episodes occur frequently in summer. The refined source apportionment of ambient volatile organic compounds (VOCs) and their ozone formation potential (OFP) during ozone pollution episodes and non-ozone pollution periods can play an important role in effectively reducing air ozone pollution in coastal cities and continuously improving ambient air quality. Therefore, this study applied the online VOCs monitoring data with hourly resolution in summer (from June to August) in 2020 in Qingdao to analyze the chemical characteristics of ambient VOCs during the ozone pollution episodes and non-ozone pollution periods and conducted the refined source apportionment of ambient VOCs and their OFP using a positive matrix factorization (PMF) model. The results showed that the average mass concentration of ambient VOCs in Qingdao in summer was 93.8 μg·m^-3, and compared with that during the non-ozone pollution period, the mass concentration of ambient VOCs during the ozone pollution episodes increased by 49.3%, and the mass concentration of aromatic hydrocarbons increased by 59.7%. The total OFP of ambient VOCs in summer was 246.3 μg·m^-3. Compared with that in the non-ozone pollution period, the total OFP of ambient VOCs in the ozone pollution episodes increased by 43.1%; that of alkanes increased the most, reaching 58.8%. M-ethyltoluene and 2,3-dimethylpentane were the species with the largest increase in OFP and its proportion during the ozone pollution episodes. The main contributors of ambient VOCs in Qingdao in summer were diesel vehicles (11.2%), solvent use (4.7%), liquefied petroleum gas and natural gas (LPG/NG) (27.5%), gasoline vehicles (8.9%), gasoline volatilization (26.6%), emissions of combustion- and petrochemical-related enterprises (16.4%), and plant emissions (4.8%). Compared with that in the non-ozone pollution period, the contribution concentration of LPG/NG in the ozone pollution episodes increased by 16.4 μg·m^-3, which was the source category with the largest increase. The contribution concentration of plant emissions increased by 88.6% in the ozone pollution episodes, which was the source category with the highest increase rate. In addition, emissions from combustion- and petrochemical-related enterprises were the largest contributor to the OFP of ambient VOCs in summer in Qingdao, with its OFP and contribution proportion being 38.0 μg·m^-3and 24.5%, respectively, followed by that of LPG/NG and gasoline volatilization. Compared with the non-ozone pollution period, the total contributions of LPG/NG, gasoline volatilization, and solvent use to the increase in OFP for ambient VOCs in the ozone pollution episodes were 74.1%, which were the main contribution source categories.

[Chemical Composition of VOCs from Service Stations Vapor Processing Device and Associated Contributions to Secondary Pollution]

Vapor processing device is a device that can control the headspace pressure in the underground storage tanks and recover the vapor. By analyzing the chemical composition of volatile organic compounds (VOCs) at the inlet and outlet of the vapor processing device, the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP) were estimated by maximum incremental reaction (MIR) and fractional aerosol coefficients (FAC), and the secondary pollution formation contribution of VOCs were quantitatively evaluated. The results showed that:① the ρ(total volatile organic compounds, TVOC) at the inlet and outlet of the vapor processing device were 436-706 g·m^-3 and 4.98-10.04 g·m^-3, respectively. Alkanes (72%±4%), oxygenated organics (14%±2%), and olefins (11%±5%) were the dominant components of VOCs emissions. There were little differences in VOCs emissions from the different vapor processing devices; the key species were i-pentane (approximately 25%), followed by n-butane, i-butane, and n-pentane. ② The ozone source reactivity (SR) of VOCs emissions from the outlet of the vapor processing device was 2.6-3.3 g·g^-1, and the OFP was 3.5-25.6 g·m^-3. Olefins contributed the most (43%-69%), followed by alkanes (20%-35%) and oxygenated organics (10%-22%). Butene, cis-2-butene, trans-2-butene, i-pentane, and propionaldehyde were the species that highly contributed to OFP. ③ Aromatics in VOCs emissions contributed the most to SOAP (80%-92%), and the main active species were toluene, 1, 2, 4-trimethylbenzene, 1, 3, 5-trimethylbenzene, and p-diethylbenzene. The research showed that different VOCs species emitted by the vapor processing device contributed obvious differences to the secondary atmospheric pollution, and butene species and aromatics such as toluene were the focus of VOCs emission control of vehicle gasoline and vapor processing device.

[Vertical Distribution Characteristics of Boundary Layer Volatile Organic Compounds in Autumn in the Mixed Industrial and Rural Areas over the Northern Suburb of Nanjing]

Based on the sounding data of VOCs in the lower troposphere (0-1000 m) in the northern suburb of Nanjing in the autumn of 2020, the vertical profile distribution, diurnal variation, and photochemical reactivity of VOCs in this area were analyzed. The results showed that the volume fraction of VOCs decreased with the increase in height (72.1×10^-9±28.1×10^-9-56.4×10^-9±24.8×10^-9). Alkanes at all heights accounted for the largest proportion (68%-75%), followed by aromatics (10%-12%), halohydrocarbons (10%-11%), alkenes (3%-7%), and acetylene (2%). The diurnal variation of the boundary layer had a great influence on the VOCs profile. The lower boundary layer in the morning and evening caused the volume fraction of VOCs to accumulate near the ground and lower in the upper layer. The vertical distribution of VOCs was more uniform in the afternoon. In the morning, the volume fraction proportion of alkenes (alkanes) with strong (weak) photochemical reactivity decreased (increased) with the increase in height, indicating that the photochemical aging of VOCs in the upper layer was significant. In the afternoon, the vertical distribution of VOCs volume fraction and OFP in the lower troposphere were more uniform. Affected by the surrounding air masses with different sources, the volume fraction and component proportion of VOCs at each height were significantly different. The alkanes in rural air masses were vertically evenly distributed, and the proportion increased gradually with the height. The vertical negative gradient of VOCs volume fraction in the urban air mass was the largest, the volume fraction of VOCs near the ground was high, and it was rich in aromatics. The proportion of aromatics increased with the increase in VOCs volume fraction between 200-400 m height of industrial air mass. The near-surface VOCs volume fraction of the highway traffic air mass was high, and alkanes accounted for the largest proportion.

[Real-time Composition and Sources of VOCs in Summer in Wuhan]

The hourly concentrations of 102 volatile organic compounds (VOCs) in Wuhan from June to July in 2019 were obtained using an online monitoring instrument. The ρ(VOCs) varied from 24.9 to 254 μg·m^-3, with a mean value of (67.7±32.2) μg·m^-3. According to the air quality standard of ozone, the observation period was divided into clean and polluted episodes of O₃. The differences in meteorological parameters, VOC concentrations, compositions, sources, and ozone formation potential (OFP) between clean and polluted episodes were analyzed and compared. The average mass concentrations of NO_x, CO, and VOCs in polluted periods exceeded those of clean periods by 34.9%, 25.0%, and 27.8%, respectively. The mass concentrations of alkanes, alkenes, aromatic hydrocarbons, and oxygenated volatile organic compounds in polluted periods were higher than those in clean periods by 40.7%, 39.5%, 26.9%, and 21.5%, respectively. The average OFP in polluted periods[(102±69.6) μg·m^-3] exceeded that of clean periods by 33.5%. The average contribution rates of LPG combustion, industrial sources, vehicle emissions, natural sources, and solvent usage to VOCs were 3.4%, 2.5%, 0.2%, 1.3%, and 1.4% lower than those of the clean periods, respectively, whereas the gasoline evaporation increased by 8.8% in polluted periods. The contributions of vehicle emissions and gasoline evaporation exhibited higher values in the morning and evening, with lower values in the afternoon, which may have been related to peak vehicles emissions. The contribution of LPG combustion peaked along with the cooking time. The concentration weighted trajectory showed that the main sources of VOCs in polluted periods were from local emissions and surrounding regions in the northeastern direction of Wuhan. In polluted periods, gasoline evaporation and LPG combustion should be emphasized for preventing O₃ pollution in the summer in Wuhan.

[Pollution Characteristics and Source Apportionment of Atmospheric Volatile Organic Compounds in Summer in Yuncheng City]

Based on the online monitoring data of VOCs, O₃, and NO₂ in Yuncheng City from June to August 2020, the pollution characteristics of VOCs in Yuncheng City in summer were analyzed. At the same time, the main emission sources were determined using a PMF model, and the chemical reactivity of VOCs was evaluated using the maximum incremental reactivity (MIR) method and fractional aerosol coefficients (FAC). The results showed that the urban area of Yuncheng was seriously polluted by VOCs and NO₂ in the early morning and evening during summer, the peak value of VOCs daily variation occurred at 08:00 and 20:00, respectively, and was mainly affected by the morning and evening peaks in traffic. The ρ(VOCs) from June to August was 50.52 μg·m^-3, and the species with the highest proportion were alkanes (39.39%) and oxygenated volatile organic compounds (OVOCs, 34.63%). Five VOCs emission sources were determined by the PMF model, of which the largest contribution was from motor vehicle exhaust emission sources (33.10%), followed by industrial emission sources (29.46%), natural gas and coal combustion sources (17.31%), solvent use sources (11.94%), and plant emission sources (8.19%). Controlling motor vehicle exhaust emission sources is the key to alleviate VOCs pollution in summer in Yuncheng City. The average ozone formation potential (OFP) of VOCs was 162.88 μg·m^-3, in which OVOCs had the highest contribution rate (45.37%); acetaldehyde, propionaldehyde, ethylene, isoprene, and toluene were the key active components; and industrial emission sources were the emission sources with the highest contribution rate. The average value of secondary organic aerosol formation potential (SOA_p) of VOCs was 0.40 μg·m^-3, in which the contribution rate of aromatic hydrocarbons was the highest (88.00%), and the solvent use source was the emission source with the highest contribution rate.

[Coordinated Control of PM2.5 and O3 in Hangzhou Based on SOA and O3 Formation Potential]

A continuous observation campaign was carried out with the Syntech Spectras GC955 volatile organics online monitoring system from March 1, 2019 to May 31, 2019 in Hangzhou. The constituent features of VOCs, the preferred VOCs species, and VOCs characteristic pollutant ratios were analyzed. The results showed that alkanes were the most important component in the volume fraction of VOCs, accounting for 62.40%. C2-C6 alkanes, benzene series, ethylene, and acetylene were the key species of VOCs. Olefins and aromatics were the main contribution components of OFP, with contribution rates of 41.35% and 37.50%, respectively. Aromatics were the main contributors to SOA, with a contribution rate of more than 90%. Low carbon alkanes, low carbon olefins, and benzene series were the key contributing species of OFP. Controlling toluene, m/p-xylene, and o-xylene is the key to the coordinated control of O₃ and PM_2.5. VOCs in the atmosphere of the sampling point were not only affected by motor vehicle exhaust but were also significantly affected by industrial emissions, such as solvents.

[Characteristics and Sources of PM2.5-O3 Compound Pollution in Tianjin]

The characteristics and sources of PM_2.5-O₃ compound pollution were analyzed based on the high-resolution online monitoring data of PM_2.5, O₃ and volatile organic compounds(VOCs) observed in Tianjin from 2017 to 2019. The results showed that total PM_2.5-O₃ compound pollution was 34 days, which only appeared between March and September and slightly increased by year. The peak value of ρ(O₃)(301-326 μg·m^-3) appeared when ρ(PM_2.5) ranged from 75 μg·m^-3 to 85 μg·m^-3. During PM_2.5-O₃ compound pollution, the average ρ(VOCs) was 72.59 μg·m^-3, and the chemical compositions of VOCs were alkanes, aromatics, alkenes, and alkynes, accounting for 61.51%, 20.38%, 11.54%, and 6.57% of VOCs concentration on average, respectively. The concentration of the top 20 species of VOCs increased, among which the proportion of alkane species such as ethane, n-butane, isobutane, and isopentane increased; the proportion of alkenes and alkynes decreased slightly; and the proportion of benzene and 1,2,3-trimethylbenzene of aromatic hydrocarbons increased slightly. The ozone formation potential(OFP) contribution of alkanes, alkenes, aromatics, and alkynes were 19.68%, 39.99%, 38.08%, and 2.25%, respectively; the contributions of alkanes, alkenes, and aromatics to secondary organic aerosol(SOA) formation potential were 7.94%, 2.17%, and 89.89%, respectively. Compared with that of non-compound pollution, the contribution of alkanes and aromatics to OFP increased 13.8% and 4.3%, and that to SOA formation potential increased 2.3% and 0.2%, respectively. The contribution of alkenes to OFP and SOA formation potential decreased 9.4% and 15.6%, respectively, and the contribution of alkynes to OFP increased 7.7% in compound pollution. The contributions of main species such as 1-pentene, n-butane, methyl cyclopentane, isopentane, 1,2,3-trimethylene, propane, toluene, acetylene, o-xylene, ethylbenzene, m-ethyltoluene, and m/p-xylene to OFP increased, and that of isoprene to OFP decreased. The contribution of benzene, 1,2,3-trimethylbenzene, toluene, and o-xylene to the potential formation of SOA increased during compound pollution. Positive matrix factorization was applied to estimate the contributions of sources to OFP and SOA formation potential in compound pollution, solvent usage, automobile exhaust, petrochemical industrial emission, natural source, liquefied petroleum gas(LPG) evaporation, combustion source, gasoline evaporation, and other industrial process sources were identified as major sources of OFP and SOA formation potential; the contributions of each source to OFP were 21.9%, 16.9%, 16.7%, 12.4%, 8.3%, 7.7%, 2.9%, and 13.2%, respectively, and to SOA formation potentials were 46.8%, 14.4%, 7.1%, 11.9%, 5.9%, 6.6%, 1.6%, and 5.7%, respectively. Solvent usage, automobile exhaust, and petrochemical industrial emissions were main sources for PM_2.5-O₃ compound pollution.

[Characteristics and Source Analysis of VOCs Pollution During the Period of Ozone Exceeding the Standard in Zibo City]

In recent years, ozone pollution has been growing increasingly serious in the urban areas of China. Volatile organic compounds (VOCs) are important precursors of O₃ formation, which is of great significance to studying the main characteristics and sources of VOCs for controlling O₃ pollution. In this study, we conducted online VOCs observation in Zibo City from May to September in 2019, monitoring 56 species in total. During the observation, the over-standard rate of ozone was up to 67.8%, the average of ρ(VOCs) was 140.71 μg·m^-3, and the concentration of VOCs in the ozone over standard days was 1.04 times that on the non-standard days. The rank of VOC classes was aromatic hydrocarbons>alkanes>alkenes>alkynes. Among them, 1,3,5-tritoluene, o-ethyltoluene, 1-butene, and n-hexane achieved high emission in the exceeding O₃ and non-exceeding days. Aromatic hydrocarbon and alkenes contributed more to the potential of ozone formation. According to the PMF source analysis results, VOCs sources in the urban area mainly included motor vehicle sources, fixed combustion sources, solvent sources, process sources, and natural plant sources, among which motor vehicle sources were the most important source of VOCs in the urban area. In addition, motor vehicle sources accounted for 32.3%, and fixed combustion sources accounted for 24.2% on days when ozone exceeded the standard, which increased by 3.3% and 6.9%, respectively, compared with those on days when ozone did not exceed the standard. However, the proportion of solvent sources and process sources decreased by 5.1% when ozone exceeded the standard compared with that on a non-standard day.

[Emission Characterstics of VOCs and n-alkanes from Diesel Forklifts]

Non-road diesel vehicle exhaust is an important emission source that affects air quality in China, yet knowledge regarding its chemical composition and potential influence factors remains limited. Six typical forklifts were selected to study the effect of diesel particulate filters (DPF) on the emission characteristics of volatile organic compounds (VOCs) and n-alkanes using online monitoring of gaseous components combined with offline analysis. The results showed that oxygenated volatile organic compounds (OVOCs), olefins, alkanes, aromatic hydrocarbons, and halogenated hydrocarbons accounted for 26%-37%, 16%-36%, 19%-22%, 13%-21%, and 4%-7% of the measured VOCs in forklift exhaust, respectively. The VOCs emission factors of low-power and high-power forklifts were(2.47±0.33)g·kg^-1 and (1.48±0.24)g·kg^-1, respectively. The forklift exhaust emission factors of total VOCs without and with DPF were(1.94±0.58)g·kg^-1and (2.08±0.79)g·kg^-1, respectively. Our results showed that DDF exerted minor impact on VOCs emission. However, it is worth noting that DPF can efficiently remove some types of OVOCs components. For example, the emission factors of acetaldehyde and acetone of the forklifts with DPF were reduced by 19% and 26%, respectively, compared to that of those without DPF. The carbon numbers of n-alkane fractions showed a bimodal distribution of C₇-C₁₇ and C₂₄-C₃₁, respectively, with C₁₅ being the dominant peak carbon. The average emission factors of n-alkanes were (115±34) mg·kg^-1 (without DPF) and (53.7±19)mg·kg^-1 (with DPF), respectively, with a decrease of 53%, indicating that DPF can effectively reduce the emission of n-alkane in the exhaust of forklifts. Our results can provide scientific support for the precise control of non-road construction machinery exhaust emissions and the further improvement of regional air quality.

[Improved Performance of PMF Source Apportionment for Volatile Organic Compounds Based on Classification of VOCs' Aging Degree in Air Mass]

VOCs are the key precursors of ozone and secondary organic aerosols. The results of source apportionment for VOCs are very important for the coordinated control of ozone and second organic particulate matter. However, VOCs do not fully meet the assumption of the receptor model because the VOCs released from each source are relatively unstable in the transmission process for their reactivity. As a result, we do not accurately obtain the actual source contribution when the receptor model is used for the source apportionment of VOCs. In order to solve the problem that the relative changes in the components caused by VOCs reactivity are not consistent with the PMF model hypothesis, the aging degree of VOCs was introduced to distinguish the state characteristics after their photochemical reactions in the ambient air. According to the ratio of ethylbenzene to m/p-xylene, VOCs monitored at Wuhai were divided into three aging states:high, medium, and low. The results showed that the model parameters, such as regression equation parameters (slope and intercept), standard error, determination coefficient, and pass rate of residual error, were improved obviously compared to the sample set after classification. Because the degree of aging is closely related to the transport time of air mass and the atmospheric oxidation in the atmosphere, it also reflects the different sources of air mass to some extent. In the high-aging VOCs samples, the coking source occupied a high proportion (up to 47.20%). In the low-aging VOCs samples, the combustion source and coking source accounted for a higher proportion, 28.67% and 24.39%, respectively. After the classification according to the aging degree, the results of VOCs source apportionment by PMF are more consistent with the actual contribution of emission sources.

[Characteristics and Source Apportionment of Ambient VOCs in Lhasa]

Due to the high altitude of plateau cities and strong ultraviolet radiation, the sources and fates of volatile organic compounds show unique characteristics. In this study, the atmospheric volatile organic compound (VOCs) samples were collected at two urban sites and one background site using tank sampling in Lhasa in 2019, and then the composition, concentration, and sources were characterized. The results showed that the average φ(VOCs) in Lhasa was 49.83×10^-9, of which the proportion of alkanes was the highest (61%), followed by OVOCs (12%), halogenated hydrocarbons (9%), olefin (9%), aromatic hydrocarbons (5%), and alkynes (4%). The respective contributions of VOCs sources at urban sites, such as Barkhor Street and Radiation Station in Lhasa, were as follows:combustion (64% and 48%) > traffic emission (17% and 31%) > industrial emission (14% and 14%) > solvents and coatings (3% and 3%) ≈plant+background (2% and 4%). The contribution of combustion was large mostly due to local incense burning (especially at Barkhor Street) and heating emissions. Traffic emissions contributed about one third to the VOCs at Radiation Station, which is related to its proximity to the transportation hub and the storage and logistics center upwind. Industrial emissions have a regional impact on ambient VOCs. Under the synergistic influence of meteorology and emissions, VOCs concentration, composition characteristics, and source contribution showed obvious seasonal variations and site differences in the Lhasa area.

[Characteristics of VOCs and Formation Potentials of O3 and SOA in Autumn and Winter in Tongchuan, China]

Volatile organic compounds (VOCs) are the main precursors of tropospheric O₃ and secondary organic aerosol (SOA), which can enhance atmospheric oxidation, promote the formation of secondary pollutants, and affect regional air quality and human health. In order to gain insights on VOCs characteristics and their potentials for O₃ and SOA formation, the volume fraction of 102 VOCs in autumn and winter in the urban area of Tongchuan were monitored using the TH-300B online monitoring system. The maximum incremental reactivity (MIR) coefficient and the fractional aerosol coefficient (FAC) were used to estimate the ozone formation potential (OFP) and SOA formation potential (SOAFP), respectively. The φ(TVOC, total VOCs) were (50.52±16.81)×10^-9 in autumn and (63.21±35.24)×10^-9 in winter. The OFPs were 138.43×10^-9 in autumn and 137.123×10^-9 in winter, and the SOAFPs were 3.098 μg·m^-3 and 0.612 μg·m^-3, respectively. Alkanes (26.19%) and aromatics (26.04%) were the most abundant species in autumn, and alkanes (48.88%) were the most abundant species in winter. Trans-2-pentene, toluene, and m/p-xylene were the most reactive species in terms of OFPs in autumn, and ethylene, acetylene, and propylene were the top three species contributing to the total OFPs in winter. Toluene, m/p-xylene, and ethylbenzene contributed the most to the total SOAFPs in both of autumn and winter. Traffic emissions were considered as the major source of VOCs in both seasons. VOCs from biomass/coal combustion emissions showed seasonal differences, which were more prominent in winter. The results can provide references for the "one city, one policy" to mitigate regional VOCs pollution and improve ambient air quality.

[Role of Atmospheric VOCs in Ozone Formation in Summer in Shanghai Suburb]

In order to study the role of VOCs in the formation of ozone during the high ozone season in summer in Shanghai, 103 volatile organic compounds, ozone, and nitrogen oxides were measured at state ecology and environment scientific observation and research station for the Yangtze River Delta at Dianeshan Lake from May to August 2018. The average volume fraction of VOCs was 32.7×10^-9 during the high ozone season in Shanghai. Carbonyl compounds were the main components of VOCs, accounting for 35.0%. Among the carbonyl compounds, the volume fraction of formaldehyde was the highest, followed by acetone, accounting for 82.8% of the total carbonyl compounds. The chemical reaction activity of ambient air was the strongest in May, and the total ozone formation potential (OFP) was 337.2 μg·m^-3. Formaldehyde had the highest contribution. The examination of the diurnal variations in alkanes, alkenes, and aromatics revealed higher average concentrations at nighttime than at daytime, with a small peak in the morning, which was related to the impact of traffic emissions. Aldehydes and ketones varied diurnally by having higher average concentrations during the daytime than those at nighttime, which was related to the secondary formation process of photochemical reactions. The observation-based model (OBM) showed that O₃ formation was in a VOC-limited regime from May to June and in a transition regime from July to August.

[VOCs Emission Inventory and Uncertainty Analysis of Industry in Qingdao Based on Latin Hypercube Sampling and Monte Carlo Method]

In recent years, fine particulate matter(PM_2.5) and ozone(O₃) have become the main air pollutants in cities in China. Volatile organic compounds(VOCs) are one of the important precursors of PM_2.5, O₃, and secondary organic aerosols. The establishment of VOCs emission inventory is therefore of great significance for controlling the amount of PM_2.5 and O₃. To date, the coefficient method has been used, which has error transmission of activity level, parameter and model, leading to the uncertainty of emission inventory. Multivariate uncertainty quantitative analysis of VOCs emission inventory provides an accurate alternative which has not been reported in China. The bottom-up method is adopted to collect the activity level of each enterprise. The variables of pollution control measures are obtained from surveys conducted with enterprises. The VOCs emission inventory of Qingdao from industrial source is established using an optimized coefficient method. The uncertainty of the VOCs inventory on the impact of univariate and multivariate variables is simulated by combining the Monte Carlo method(MC) with Latin hypercube sampling method(LHS). The results show that the total VOCs emissions were 44700 tons from industrial sources in 2019(unoptimized coefficient method:31100 tons).The rubber and plastic industries, metal products, and oil/coal/other fuel processing contributed more VOCs, which accounted for 40.26% of the total emissions. The uncertainty of multivariate simulation is higher than that of single variable. The uncertainty from process(-9.72%-230.51%) and solvent using source(-14.14%-122.77%) is significantly higher than uncertainty from combustion source(-15.62%-36.41%). The main sectors affecting the uncertainty of the VOCs inventory include:the chemical, papermaking, and textile industries(emission factors); metal, automobile manufacturing, and chemical industries(removal rate, facility operating rate); industries of petroleum processing and ferrous metal smelting(too few samples). VOCs emissions are mainly distributed in the east of the West Coast New district, north of Dazhu Mountain, south of Jimo district, north of Chengyang district, northeast of Jiaozhou district, built-up area of Pingdu district, and southeast of Laixi district.

[Characteristics of Industrial Volatile Organic Compounds(VOCs) Emission in China from 2011 to 2019]

In order to better understand the industrial volatile organic compounds(VOCs) emissions in China in recent years, an industrial VOCs emission inventory was developed from 2011 to 2019, based on the dynamic emission factors method and the comprehensive source classification system. The results showed that VOCs emissions increased first from 11122.7 kt in 2011 to 13397.9 kt in 2017, and then decreased to 13247.0 kt in 2019. The emission structure of the four source categories changed. The contribution from basic organic chemical industries, gasoline storage and transportation, manufacturing(i.e., coatings, inks, pigments, and similar products), and industrial protective coatings continued to increase. On the contrary, the contributions of oil and natural gas processing, automobile, and container manufacturing industries declined over the study period. Among the industrial emissions in China in 2019, industrial coating, printing, and basic organic chemical industries emitted large amounts of VOCs(accounting for 39.2% of the total emission), and because their contribution became increasingly prominent since 2011, these sectors will be the key emission sources in the future. With respect to the spatial distribution in 2019, East China and South China had the largest VOCs emissions. Shandong, Guangdong, Jiangsu, and Zhejiang were the four provinces that contributed the most, accounting for 40.6% of the total VOCs emissions.

[Volatile Organic Compounds(VOCs) Emission Inventory from Domestic Sources in China]

A volatile organic compounds(VOCs) emission source classification and accounting system from domestic sources in China was established for the period between 2010 and 2018. Suggestions for the prevention and treatment of VOCs from domestic sources were developed and proposed. The results showed that the total VOCs emission inventory from domestic sources in China in 2018 was 2518 kt. Architectural decoration, asphalt road paving, cooking, and rural household biomass use source were the four largest contributors, accounting for 69.22% of the total emissions. Chemical household products and urban and rural coal use contributed equally, accounting for 10.43% and 9.98%, respectively, whilst car repair accounted for 7.75%. Shandong, Sichuan, Henan, Guangdong, Jiangsu, and Hebei were the six provinces that contributed the most(36.01%). During the 2010-2018 period, China's domestic VOCs emissions increased at a rate of 0.43%, and after reaching a peak in 2013, the emissions began to decline at a rate of 2.23%. The reason for the decline was that, on the one hand, the cleaner energy consumption of residents made a contribution to the gradual reduction of domestic coal and biomass consumption. On the other hand, the gradual saturation of housing construction in some areas, which led to a decrease in the annual construction of the country. It is recommended to promote the comprehensive management of architectural decoration, cooking methods, and car repair, while paying attention to the VOCs emissions from asphalt road paving. Meanwhile, continue to optimize the energy use structure of domestic sources, and promote the pollution control of civil coal and household biomass combustion in accordance with local regulations and multiple measures.

[Pollution Characteristics and Ozone Formation Potential of Ambient VOCs in Different Functional Zones of Shenyang, China]

Ambient volatile organic compounds(VOCs) were determined by GC 5000 online gas chromatography in three functional areas of Shenyang, namely industrial, traffic, and mixed cultural and educational areas. The pollution characteristics of VOCs in these functional areas during the heating and non-heating periods were analyzed, and the ozone formation potential(OFP) was estimated by using maximum incremental reactivity(MIR). The results show that the average mass concentration of VOCs is(82.19±54.99) μg·m^-3 in Shenyang, of which the concentration in industrial areas is significantly higher than that in traffic and cultural and educational mixed areas, and the heating period is higher. The traffic and mixed cultural and educational areas have bi-modal characteristics due to the morning and evening traffic, and the industrial area has multiple peaks affected by the irregular operation hours. The proportion of VOCs in traffic and mixed cultural and educational areas shows the order of alkanes>aromatic hydrocarbons>alkenes>alkynes, but the proportion of alkynes in industrial areas is higher than that of alkenes. The benzene to toluene(B/T) and ethane to acetylene(E/A) ratios reflects that traffic and mixed cultural and educational areas were affected by both vehicle exhaust emissions and fuel combustion. The industrial zone is therefore affected by complex sources, and there are more aged air masses during the heating period than non-heating period. The average OFP contribution of atmospheric VOCs in Shenyang is 232.89 μg·m^-3. The contribution of alkenes is largest for all functional areas, and the aromatic component also contributes more due to the high concentration of industrial areas.

[Emission Characteristics and Environment Impacts of VOCs from Typical Rubber Manufacture]

The emission characteristics of VOCs from three typical rubber manufacture industries were studied by GC-MS/FID. Maximum incremental reactivity(MIR) and fractional aerosol coefficient(FAC) were employed to evaluate the ozone formation potential(OFP) and secondary organic aerosol(SOA) formation potential. The results show that the VOC types emitted from the manufacturing of rubber products mainly include alkanes, ketones, aldehydes, alcohols, and benzene series. For traditional rubber products manufactured through rubber mixing and vulcanization, the main pollutants are ketones and alcohols, whereas for production processes involving gluing and painting, the main pollutants belong to the benzene series. In terms of ozone impact, the traditional processes contribute to ozone formation mainly through oxygenated hydrocarbons. In industries that utilize adhesives and paints, the extensive use of these organic solvents lead to a significantly higher contribution of the benzene series than other VOC species to ozone formation; the benzene series account for 82.9% of the total contribution. In terms of SOA impact, the benzene series are the main contributor to SOA, whereas the contribution of VOCs from traditional processes is small; hence, SOA primarily originates from the gluing and painting processes. Therefore, in traditional production of rubber products through rubber mixing and vulcanization, the emission of oxygenated hydrocarbons should be preferentially controlled, whereas for rubber industries utilizing gluing and painting processes, the emission of benzene series should be preferentially controlled.

[Characteristics and Source of VOCs During O3 Pollution Between August to September, Langfang Development Zones]

A total of 99 volatile organic compound(VOC) species were detected the Langfang development zones based on continuous monitoring using a ZF-PKU-1007 between August 25 and September 30, 2018. The concentrations, reactivity, and sources of VOCs were studied under different O₃ concentrations using compositional analysis. The results showed that the average VOCs concentration during the research period was(75.17±38.67)×10^-9, and was(112.33±30.96)×10^-9, (66.25±34.84)×10^-9 on pollution days and cleaning days, respectively(VOCs concentrations were 69.6% higher on pollution days). The contribution of VOCs species to the ozone formation potential(OFP) were ranked in the order aldehydes > aromatics > alkenes > alkanes. In the case of L_·OH, the main contributions were from aromatics(30.0%) and alkenes(25.8%) on pollution days, while the contribution from aromatic alkenes(29.8%) was a slightly higher than aromatics(28.0%) on cleaning days. By applying the positive matrix factorization(PMF) model, five major VOCs sources were extracted, namely vehicle emissions(34.4%), solvent usage and evaporation(31.7%), the petrochemical industry(15.7%), combustion(11.1%), and plant emissions(7.9%). The contributions of solvent usage and evaporation and plant emission sources on pollution days were 13.1% and 1.2% higher than on cleaning days, respectively, which was likely due to relatively higher temperatures on these days. Therefore, vehicle emissions and solvent usage and evaporation should be priorities in VOCs control strategies for the Langfang development zones between August to September.

[Coating-derived VOCs Emission Characteristics and Environmental Impacts from the Furniture Industry in Guangdong Province]

To determine the differences in emissions among different types of coatings, such as solvent-based, water-based, solvent-based ultra-violet(UV), water-based UV, and powder coatings, representative furniture manufacturing companies were selected for analysis. The emission concentrations and compositional characteristics of volatile organic compounds(VOCs) in different types of coatings were compared and studied. The ozone formation potential(OFP) and secondary organic aerosol formation potential(SOAFP) of the different types of coatings were also analyzed. Solvent-based coatings has higher TVOC concentrations, OFPs, and SOAFPs than water-based, solvent-based UV, water-based UV, and powder coatings. The concentrations and composition of VOCs emitted from the different types of coatings were also different. The main VOC groups of the solvent-based and solvent-based UV coatings were aromatic hydrocarbons and oxygenated volatile organic compounds(OVOCs). Specifically, the proportions of aromatic hydrocarbons are 41.91%-60.67% and 42.51%-43.00%, respectively, and the proportions of OVOCs were 24.75%-41.29% and 41.34%-43.21%, respectively. OVOCs accounted for the highest proportion of VOCs in the water-based, water-based UV, and powder coatings, at 54.02%-62.10%, 55.23%-64.81%, and 42.98%-46.45%, respectively. The major VOC compound of the solvent-based coatings was styrene(14.68%), and the main component of the water-based coatings was methylal(14.61%). The main species of VOCs from the solvent-based UV and water-based UV coatings were butyl acetate(15.36% and 20.56%, respectively). The most abundant species from the powder coatings was ethyl 3-ethoxy propionate(20.19%). Aromatic hydrocarbons were the most important contributor to the OFP of the solvent-based and solvent-based UV coatings, accounting for 79.84% and 80.32%, respectively. Aromatic hydrocarbons(51.48% and 36.71%) and OVOCs(42.30% and 41.03%) were the major contributors to the OFP of the water-based and water-based UV coatings, respectively. Aromatic hydrocarbons(43.46%), OVOCs(28.06%), and olefins(25.24%) were the main factors affecting the OFP of the powder coatings. Aromatic hydrocarbons dominate the SOAFP of solvent-based, water-based, solvent-based UV, water-based UV, and powder coatings, accounting for more than 99%.

[Multidimensional Verification of Anthropogenic VOCs Emissions Inventory Through Satellite Retrievals and Ground Observations]

In this paper, a regional emissions inventory of anthropogenic VOCs was established based on the traditional emissions factor method for the Beijing-Tianjin-Hebei (BTH) region, followed by a multidimensional calibration study based on regional satellite remote sensing information for formaldehyde and typical urban ground VOCs. Inventory calculations showed that the VOCs emissions in BTH in 2013, 2015, and 2017 were 2026700, 2073400, and 1934200 tons, respectively, comprising alkanes (29.83% to 30.72%), unsaturated hydrocarbons (16.54% to 17.68%), aromatic hydrocarbons (27.14% to 27.51%), aldehydes (8.75% to 9.52%), ketones (8.13% to 9.04%), and aldehydes and ketones lipids (5.13% to 6.60%). During 2013-2017, the emission of VOCs in Zhangjiakou, Qinhuangdao, and Hengshui increased slightly (1.10% to 1.66% per year); emissions in Xingtai and Handan decreased slightly (-1.46% to -1.12% per year); and emissions in Chengde, Tangshan, Baoding, and Cangzhou were stable. There trends were consistent with the inter-annual trend of satellite-derived HCHO column concentrations. However, in Beijing, Tianjin, Langfang, and Shijiazhuang, annual variations in VOCs emissions (-6.51%, -3.30%, 2.16%, and 0.11% per year) and HCHO column concentrations (-1.17%, 7.19%, -0.24%, and 6.68% per year) were observed, respectively. In the regional VOCs inventory, a good linear correlation (R>0.5) was achieved between the grid emissions of VOCs and HCHO column concentrations in urban areas, while the correlation was only 0.33 in suburban areas. This is mainly due to the important influence of secondary conversion of VOCs originating from natural sources to HCHO in suburban areas. In addition, ground-level VOCs concentrations were observed in the urban areas of Beijing and Handan, where the emission ratios (ERs) of VOCs and CO were regressed. The ERs of most hydrocarbons were in good agreement with the regressed ERs, but the ERs of ethane were significantly lower (-156% to -73%) and the ERs of aromatic hydrocarbons above C8 were relatively high (54% to 74%). In general, the regional anthropogenic VOCs emissions inventory established in this paper offers high accuracy and reliability.

[Spatio-Temporal Evolution Characteristics and Source Apportionment of O3 and NO2 in Shijiazhuang]

Ground-level O₃, NO₂, and meteorological (temperature, humidity, wind speed, precipitation, and sunshine duration) data from 18 counties in Shijiazhuang City from 2014 to 2017, and volatile organic compounds (VOCs) data for Summer 2017, were analyzed to explore the spatial patterns, evolution, influencing factors, and source apportionment of O₃ and NO₂ in Shijiazhuang City. Network analysis and inverse distance weighted (IDW) spatial autocorrelation and backward trajectories analyses were performed. The results indicate that O₃ concentrations increased between 2014 and 2017, and monthly variations showed a unimodal trend. The typical period of peak O₃ pollution (O₃ ≥ 160 μg·m^-3) was from May to September, characterized by high temperatures, low humidity, weak winds, and strong solar radiation. The O₃ concentrations were negatively correlated with the NO₂. Furthermore, O₃ concentrations increased year-on-year since 2015 in main urban area, and the dominant pollutant type had changed from NO₂ (2014 to 2016) to VOCs (2016 and 2017). However, the O₃ concentration of county-areas limited by the VOCs. The main factors affecting O₃ concentrations were industry, agriculture, economy, and population, and centers of O₃ pollution associated with secondary industry appeared in the main urban areas of Shijiazhuang and Luancheng. Moreover, VOCs trajectories during the summer monitoring period were clustered in three source directions:(A) East-northeast, 26.67%; (B) Northwest-west, 43.33%; and (C) Southeast-south, 30%). Trajectories (A) and (C) were the dominant directions of VOC transmission (east-southeast).

[Source Apportionment of Ozone Pollution in Guangzhou: Case Study with the Application of Lagrangian Photochemical Trajectory Model]

A six-day ozone pollution episode in Guangzhou in early October 2018 was analyzed with the application of a Lagrangian photochemical trajectory model to trace the sources of ozone, quantify the contributions of different regions, and evaluate the effects of emission reduction measures targeted at different emission sectors and different precursors on ozone pollution. The results showed that during the ozone pollution episode, the maximum daily 8 h ozone exceeded 160 μg·m^-3 and the highest value reached 271 μg·m^-3. The average concentrations of nitrogen oxides and volatile organic compounds (VOCs) were (77.7±42.8) μg·m^-3 and (71.9±56.2) μg·m^-3, respectively. Aromatics and alkenes were the dominant reactive VOCs, with contributions of 38% and 30% to·OH reactivity and 51% and 16% to ozone formation potential, respectively. The ozone pollution in Guangzhou during this episode was affected by three types of air masses, with the primary source regions of Guangzhou, Guangdong Province, and regions outside Guangdong Province. For all three air mass types, ozone production in these source region was controlled by VOCs. Sensitivity tests showed that, in the primary source regions, reducing the emissions of VOCs is more effective than reducing NO_x in terms of reducing ozone concentrations. Under the condition of full emission reduction, regulating traffic emissions could substantially reduce ozone levels by 14.6%-21.0% in Guangzhou, which was a more significant reduction than regulating controlled industry (8.4%-15.3%), power plant (0.9%-6.2%) and residential (2.3%-4.7%) emissions. However, the traffic emission reduction is not as effective (induced ozone reduction<10%) when the emissions reduction ratio is lower than 90%. In addition, biogenic emissions in the Pearl River Delta also substantially contributed to the ozone levels under certain circumstances, as indicated by the ozone reduction up to 19% when biogenic emissions were shut off.

[Characteristics of Volatile Organic Compounds Pollution and Risk Assessment of Nansi Lake in Huaihe River Basin]

This study aimed to investigate the pollution characteristics of the volatile organic compounds in Nansi Lake and evaluate the ecological and health risks. In November 2017, water samples collected from 25 sampling points in Nansi Lake using the purge and trap technique and GC-MS detected 52 types of VOCs. The detection rate of ethylbenzene, m-/p-xylene, o-xylene, 1,2-dichlorobenzene, and naphthalene reached 100%, and cis-1,3-dichloropropene and toluene reached 96%. The detection rate of 1,2,4-trimethyl benzene was the lowest, at only 12%, the average concentration of 1,2-dichlorobenzene was the highest, reaching 3.49 μg·L^-1, and 1,2,4-trimethyl benzene was only 0.02 μg·L^-1. The concentration of 1,2-dichlorobenzene in Nansi Lake was generally higher than that of other VOCs. Meanwhile, the concentrations of m-/p-xylene and ethylbenzene at point NSH-24 far exceeded the other VOCs, but the median value of all VOCs did not exceed 4 μg·L^-1. The spatial distribution of the VOCs concentrations in Nansi Lake presented high values in the northwest and southeast, and low in the middle. The leading cause of VOCs pollution in Nansi Lake may be the exhaust gas emitted by shipping vessels during navigation, and the secondary cause is the collection of VOCs in the upstream and downstream tributaries and the influence of human factors. The health risk assessment of Nansi Lake found that, overall, there was no carcinogenic or non-carcinogenic health risk, but the risk value of individual points was relatively high, even exceeding the risk threshold set by the US EPA. There were 12 points in Nansi Lake where the ecological risk quotient exceeded 1, indicating an ecological risk to aquatic organisms.

[Characterization of Volatile Organic Compounds (VOCs) Using Mobile Monitoring Around the Industrial Parks in the Yangzte River Delta Region of China]

Volatile organic compounds (VOCs) play important roles in the formation of ozone and fine particles in the troposphere. Industrial parks emit significant amounts of VOCs in China, while few studies have characterized them. In the present study, a mobile platform was employed to measure the levels and composition VOCs around industrial parks in the Yangzte River Delta region. The average concentration of VOCs ranged from 39 μg·m^-3 (5% percentile) to 533 μg·m^-3 (95% percentile) with an average of 183 μg·m^-3, which was three times that of ambient concentrations. Maximum VOC concentrations ranged from 307 μg·m^-3 (5% percentile) to 12006 μg·m^-3 (95% percentile) with an average of 2812 μg·m^-3. The frequency of abnormal peak values was as high as 64% across all the industrial parks, of which toluene (32%), xylene (18%), benzene (9%), and>C9 aromatics (19%) were the most common species. Differences in VOC characteristics were observed among the different types of industrial parks. Specifically, highest concentrations of VOCs were observed in textile industrial parks followed by chemical, painting, and petrochemical industrial parks, and VOC concentrations in electronics industrial parks were the lowest. Importantly, species measured using the mobile platform only contributed~50% of VOCs present in ambient samples, indicating that the concentrations of VOCs in the industrial parks were underestimated overall. These results can inform measures to control VOC pollution in industrial parks in China.

[Industrial Emission Characteristics and Control Countermeasures of VOCs in Chinese Rapid Economic Development Areas]

With the rapid development of China's economy, volatile organic compounds (VOCs) as the precursor of smog and ozone are of increasing concern, especially in rapidly developing areas. This paper is a systematic analysis of VOCs emissions and distribution trends in 12 typical industrial sectors, garbage and wastewater treatment plants, comprehensive industrial parks, and residential districts in Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta Regions. The results show that pharmacy, rubber producing, as well as paint spraying are the top three industries among the 12 typical industries with the highest average VOCs emission concentrations at 541, 499, and 450 mg·m^-3, respectively. By comparison, the average emission concentration of VOCs from the pharmaceutical industry in Yangtze River Delta and Beijing-Tianjin-Hebei Region was, respectively, about 112 and 1.00×10³ mg·m^-3. The paint spraying industry in the Pearl River Delta region has the highest emission rate with an average concentration of 1.04×10³ mg·m^-3. The investigation pertaining to the distribution of different VOCs categories indicates that highly toxic aromatics and halogenated hydrocarbons account for the highest emissions in paint spraying and pharmaceutical industries, reaching ratios of 55.99% and 26.57%, respectively. Additionally, among the three major economic zones, the VOCs concentration is the lowest in residential areas and comprehensive industrial parks in the Yangtze River Delta but the highest in the Beijing-Tianjin-Hebei Region, which is consistent with the distribution of industrial emissions in each region. Moreover, the research reveals that VOCs concentration in residential districts experienced a fluctuating reduction from 2002 to 2018. The significant reduction since 2016 suggests that formulated policies, laws and standards, along with the performed techniques have made significant contributions to the control of VOCs.

[VOCs Emission Inventory and Variation Characteristics of Artificial Sources in Hubei Province in the Yangtze River Economic Belt]

In this study, a 2018 anthropogenic volatile organic compounds (VOCs) emission inventory in Hubei Province was conducted using the emission factor method based on activity levels of five sources. The emission characteristics and variation trends of process sources from 2009 to 2018 were further analyzed. Total anthropogenic VOCs emissions were 6.52×10⁵ tons in Hubei Province, accounting for about 6.41% of the country's total omissions. The contributions of fossil combustion sources, process sources, solvent sources, mobile sources, and waste disposal sources were 3.26%, 76.39%, 4.54%, 14.72%, and 1.09%, respectively. Process sources involving 45 sub-categories of nine industries accounted for a significant proportion of VOCs emissions, with Wuhan and Yichang recording the highest VOCs emission levels. The VOCs emissions intensity of each city and state were analyzed based the level of economic activity and territorial area. Tianmen and Shennongjia had higher VOCs emissions per unit of GDP, while Wuhan, Ezhou, and Tianmen had higher VOCs emissions per unit area. Regarding process source contributions, VOCs emissions increased progressively to 2.45×10⁵ tons in 2009 and then stabilized between 2015 and 2017 with maximum emissions of 7.01×10⁵ tons. In 2018, VOCs emissions decreased to 4.98×10⁵ tons. This trend was similar to national anthropogenic emissions. Two industrial sectors, namely chemical raw materials and rubber and plastics, were the main driving force with contributions of 33.85%-51.55% and 7.07%-38.13%, respectively. Among them, the production of chemicals and active pesticide and pharmaceutical ingredients played an important role in contributing to VOCs emissions, while emissions during foam plastics production varied greatly, increasing sharply to more than 2.00×10⁴ tons in 2015-2017. Under the guidance of the relevant national and local policies, emissions from key industries were significantly reduced in Hubei Province.

[VOCs Removal and Emission Monitoring of Beijing Bulk Gasoline Terminals in 2012-2019]

Bulk gasoline terminals are an important emission source of volatile organic compounds (VOCs) in cities. Beijing started to promote the installation of oil and gas recovery devices at oil storage terminals in 2006 to reduce VOCs emissions, since then VOCs emissions from the terminals have been monitored by the municipal government every year. This paper analyzes the VOCs emission characteristics of oil storage terminals in Beijing from 2012 to 2019. We found that the VOCs import concentration was 165.3 g·m^-3 in 2019 and had experienced a decline-rise-decline pattern during 2012-2019. The emission concentration was 7.3 g·m^-3 in 2019 and had declined continuously during the preceding eight years. The removal efficiency of VOCs of the gas recovery devices tended to be stable and ranged from 45.5% to 100%. Although the emission concentration had decreased significantly, the removal efficiency of the recovery unit at the oil storage terminals had decreased. Therefore, this paper proposed to strengthen process management, the inspection of the service life of the oil and gas recovery units, and check and maintain records. In addition, the removal efficiency index should be included in the scope of law enforcement and "double index" requirements should be implemented This paper will provide a scientific basis for the future development of atmospheric improvement measures.

[Characteristics and Source Apportionment of VOCs and O3 in Shijiazhuang]

To study the composition characteristics and sources of volatile organic compounds (VOCs) in Shijiazhuang City, three national control points were selected to conduct VOCs sampling and analysis from March 2017 to January 2018. The correlation of VOCs through combination with meteorological and ground-level O₃ data, and the sources of VOCs were analyzed by positive matrix factorization (PMF). To quantify the pollution period of O₃ in summer, its temporal sequence characteristics were studied by wavelet analysis. During the sampling period, the average concentration of ambient total VOCs (TVOCs) was (137.23±64.62) μg·m^-3. Haloalkanes were the most dominant VOC compounds, accounting for 31.77% of total VOCs mass, followed by aromatic (30.97%) and oxygenated VOCs (OVOCs, 23.76%). The seasonal variation in VOC concentration followed the trend in winter (187.7 μg·m^-3) > autumn (146.8 μg·m^-3) > spring (133.24 μg·m^-3) > summer (107.1 μg·m^-3); the concentration of VOCs shows a trend of increasing gradient from west to east. The O₃ concentration correlated negatively with VOCs and NO₂, and positively with temperature, sunshine duration, wind speed, and visibility. Changes in meteorological elements were concerned before the occurrence of ozone pollution in summer, especially in 4-5 days in June and 7-8 days during July to August after the occurrence of increasing temperature. Finally six potential sources of VOCs were quantified by the PMF model, including from gasoline emissions (24.78%), diesel vehicle emissions (24.69%), solvent usage (18.64%), the chemical industry (11.87%), regional background (10.84%), and the pharmaceutical industry (9.17%). Ozone formation potential (OFP) contribution of emission sources of gasoline and diesel vehicles (54.98%) was over half of the total contribution. Meanwhile, these findings illustrated that control of vehicle emissions and industrial sources would be an important way to reduce VOCs concentrations and improve air quality in Shijiazhuang.

[Accurate Identification of Ambient VOCs Emission Sources in an Industrial Park Using On-Line Monitoring Data]

To accurately identify and locate ambient volatile organic compounds(VOCs)emission sources in industrial parks, a continuous online GC-FID method was used to monitor 43 kinds of VOCs on an hourly basis during January 2017 at five sites in an industrial park. A statistical analysis and a PMF model were used to analyze the sources of VOCs, and by combining with CPF and enterprise emission information, the location of each pollution source was accurately identified. The average VOCs concentration was 56.40×10^-9 and the highest concentration of alkanes was observed at four sites, with the exception of one site. Ethane, propane, ethylene, toluene, isobutane, n-butane, and acetylene were the main contributors. Ambient VOCs in the park mainly derives from five sources:urban transmission, butane leakage, process emissions, storage tank emissions, and ethylene synthesis. The enterprises in the zone B1, A1-A3, C1-C2, F4, E4-E6, F4-F6, and the canal loading and unloading area are the main emission areas of the pollution sources. Using online monitoring data, the research combined a PMF model, meteorological conditions, and corporate emissions information to achieve precise positioning of the pollution sources of VOCs in the industrial park, thus providing a basis for the supervision and management of corporate emissions in industrial parks.

[Evolution and Evaluation of O3 and VOCs in Zhengzhou During the National Traditional Games of Ethnic Minorities Period]

During the National Traditional Games of Ethnic Minorities (NTGEM) 2019, air quality in Zhengzhou was analyzed to evaluate the impact of pollution prevention and control measures on Zhengzhou. Ground-observed meteorological and pollutant data as well as the chemical compositions of volatile organic compounds (VOCs) were investigated. The results showed that the six parameters of pollutants in the safeguard period in 2019 indicated a downward trend as compared with that during the same time in 2018, and the average concentrations of PM_2.5 and PM₁₀ were decreased by 16.2% and 25.1%, respectively. However, the average concentration of O₃ was only reduced by 3.7%. The daily proportions of primary pollutants of O₃ increased to 90% during the NTGEM, and the ozone pollution was severe in this period. Meanwhile, the concentration of total volatile organic compounds (TVOCs) in the safeguard period was 26.21×10^-9, which was significantly lower than that during the historical period. Six emission sources of the VOCs were identified using PMF model, including vehicle exhaust (28%), LPG evaporation (21%), combustion source (16%), industrial emissions (15%), solvent utilization (15%), and biogenic VOCs (5%). During the NTGEM period, the control of combustion sources and industrial sources was evident.

[Emission Inventory of VOCs Components in Zhengzhou and Their Ozone Formation Potential]

In this study, according to the activity levels of volatile organic compounds (VOCs) sources and source profiles, a 2016-based inventory of the speciation emission of the VOCs was established and the ozone formation potential (OFP) were estimated in Zhengzhou. The results showed that the total VOCs emission in Zhengzhou in 2016 was 96215.3 t. The highest emission source was on-road mobile source (29.7%) followed by solvent use sources (28.1%). The species that contributed the highest emission was alkanes (29.8%) followed by aromatics (29.0%). The OFP in Zhengzhou in 2016 was 341291.0 t with the highest contributing source as on-road mobile (30.5%) followed by solvent use source (28.8%). Moreover, the light duty gasoline vehicle, use of interior wall coatings, vehicle surface coating, gas station loading and unloading, and manufacture of non-metallic mineral were the major secondary emission sources of OFP, which needed to be controlled for reducing ozone pollution in Zhengzhou. For VOCs species group, the higher contribution groups were aromatics (42.8%) and alkenes (38.9%). The sources that produced m/p-xylene, propylene, ethylene, and other species should be paid more attention.

[Component Characteristics and Source Appointment of Volatile Organic Compounds in Lianyungang City]

Volatile organic compounds (VOCs) are important precursors of ozone and particulate matter; thus, their impacts on air quality are particularly significant. To study the composition characteristics and sources of VOCs in Lianyungang City, four national control sites were selected to conduct VOCs sampling and analysis on typical days in spring, summer, and autumn. Concentrations of VOCs, the effects of different components of VOCs on ozone formation were quantified, and the sources of VOCs were analyzed using the Positive Matrix Factorization model. The VOC concentrations were in the range of 27.46×10^-9-40.52×10^-9 in spring, 45.79×10^-9-53.45×10^-9 in summer, and 38.84×10^-9-46.66×10^-9 in autumn. Concentrations of oxygenated compounds accounted for 41%-48% of all measured VOCs. VOC species with higher concentrations were acetone, acrolein, and propionaldehyde, and the concentration of isoprene was higher in summer. Generally, VOC concentrations were higher at 09:00 than at 13:00 when acrolein, ethylene, and dichloromethane concentrations changed greatly. The ozone formation potential (OFP) of oxygenated compounds was the highest, followed by aromatics and alkenes, and the OFP of alkanes was the smallest. The VOC species with higher OFP were acrolein, propylene, and ethylene. The main sources of VOCs in Lianyungang were industry (49%), solvent usage (23%), transportation (14%), paint usage (10%), and natural sources (4%). The results suggest further investigating the oxygenated compounds with higher concentrations and higher OFP in Lianyungang City, and studying the impacts of industrial sources on VOCs.

[Characteristics of VOCs and Their Roles in Ozone Formation at a Regional Background Site in Beijing, China]

As important precursors of near-surface ozone, secondary organic aerosols (SOAs), and volatile organic compounds (VOCs) play an important role in photochemical reactions and fine particle formation. In this study, real-time VOCs were measured continuously by Syntech Spectras GC955 analyzers at the regional background site of the North China Plain from September 1 to 27, 2017. The VOC concentration levels, compositions, spatiotemporal variations, and the ozone formation potential during the observation period were investigated. The potential sources of initial VOCs indicated from the diagnostic ratios were further studied. The averaged total mixing ratio of VOCs was 12.53×10^-9. Among all measured VOC species, alkanes were the most abundant species, which accounted for 65.3% of the total concentrations, followed by alkenes (26.7%) and aromatics (6.5%). In addition, the total OH radical loss rate of VOCs (L^·OH) was 5.2 s^-1. In particular, the contribution of C4-C5 alkenes to L^·OH was as high as 61%, followed by C2-C3 alkenes, with a 12.8% contribution of L^·OH. The average ozone formation potential of VOCs was 36.5×10^-9. Among all the measured VOC species, alkenes were the most abundant species, which accounted for 71.2%. Among alkenes, the contribution of C4-C5 alkenes was the most prominent. Although the concentration of alkanes in Shangdianzi was much higher than other VOC species, the ozone formation potential was lower. Diagnostic ratios and source implications suggested that Shangdianzi was affected mainly by biomass/biofuel/coal burning, with substantially elevated benzene levels during the observation period, whereas a slight influence of traffic-related emissions was observed.

[Producing Coefficients and Emission Coefficients of Volatile Organic Compounds from the Automobile Manufacturing Industry in Zhejiang Province]

Four typical automobile manufacturing enterprises in Zhejiang Province were selected to determine the main production and emission links of volatile organic compounds (VOCs) in this industry by analyzing their production processes and the main raw and auxiliary materials used. Two of them were monitored on the spot, and the producing coefficients and emission coefficients of the VOCs discharged from the automobile manufacturing industry in Zhejiang Province were calculated. Then, the production and emission of VOCs in this industry in 2017 in Zhejiang Province were estimated. The results show that the main production and emission links of VOCs in the automobile manufacturing industry in Zhejiang Province are coating processes. Only a few of the automobile manufacturers in Zhejiang Province can deal with the paint exhaust gas effectively at present; in addition to coatings, solvent-based cleaning agents are also one of the main sources of VOCs in this industry. The VOC producing coefficients of the automobile manufacturing industry in Zhejiang Province are 0.20 t·t^-1, 3.92 kg·vehicle^-1, and 29.36 g·m^-2; the emission coefficients are 0.13 t·t^-1, 2.63 kg·vehicle^-1, and 19.72 g·m^-2. The quantity of VOCs generated by this industry in 2017 was 2425.84 t, while the quantity of emissions was 1627.54 t.

[Emission Characteristics of Volatile Organic Compounds from Typical Industries in Zibo]

To study the emission characteristics of volatile organic compounds (VOCs) in Zibo, nine key industries and their representative enterprises were selected to conduct a field investigation and measurement. The emitted VOC characteristics in different industries were analyzed. Based on measurement data, the emissions of VOCs from all monitored enterprises were calculated to obtain the localization emission factors. The results showed that different industries exhibited some differences in VOCs components, and the major VOCs components were alkane and halo hydrocarbon. Ethane, acetylene, chloromethane (conclude 1,1-dichloroethane, 1,1,1-trichloroethane), and Freon (Freon 12 or Freon 114) were the characteristic species in most industries. The results indicated that the major VOCs emission links in different types of petrochemical industries were equipment leakage, loading volatilization, storage volatilization losses, and organized discharge, which accounted for more than 40% of emissions. Local emission factors of VOCs calculated in the synthetic rubber and steel manufacturing industries were close to the recommended values in the guide, whereas there were large gaps in other industries.

[Pollution Characteristics of Volatile Organic Compounds Emission from the Metal Packaging Industry Based on Analysis of Process]

This study identified the generation and emission nodes of volatile organic compounds (VOCs) in the metal packaging industry, analyzed the VOCs concentration and species from different production processes, and accounted for secondary pollution through the maximum incremental reactivity method and modified fractional aerosol coefficient method. The results indicated that the main VOCs species were benzenes, alcohols, ketones, and esters, and the benzenes and alcohols contributed more in different types of processes and emission nodes, whereas the ketones and esters contributed less. The maximum concentration was 269.08mg·m^-3 (n-butanol). Strong correlation was found between the concentrations of the production line and their corresponding exhaust, but the VOC species were not totally identical. Furthermore, the potential formations of ozone and secondary organic aerosols were (3.09±0.94) g·g^-1 and (2.58±1.99) g·g^-1, respectively, expressed by O₃/VOCs and SOA/VOCs, and the benzenes and internal coating drying being the major precursors and emission node.

[Analysis of Pollution Characteristics and Sources of Atmospheric VOCs in Ezhou City]

From March 2018 to February 2019, quantitative detection was made of 102 kinds of atmospheric volatile organic compounds (VOCs) using online gas chromatography in Ezhou City. We compared and analyzed the composition, seasonal variation, and diurnal variation of VOCs. Using maximum incremental reactivity (MIR), we estimated the ozone generation potential (OFP) of VOCs. The results show that the annual average volume fraction of atmospheric VOCs in Ezhou is (30.78±15.89)×10^-9, and is overall higher in winter than summer, represented by alkane > oxygen > halogenated hydrocarbon > olefin > aromatic hydrocarbon > alkyne. The night volume fraction is higher than in the daytime, and overall the distribution is "double peak". The aromatic hydrocarbons, halogenated hydrocarbons, and OVOCs appear as a "third peak" at 00:00-02:00. Aromatic hydrocarbons and olefins contribute more to the OFP potential of VOCs, with contribution rates of 35.45% and 29.5%, respectively. The highest contribution rate to OFP is ethylene, reaching 24.217%. Analysis of VOC characteristic species found that vehicle exhaust fumes and solvent volatilization are the main sources of VOCs in Ezhou. Of these, motor vehicle emissions are the most important source. Controlling Ezhou's motor vehicle emissions helps to reduce the composition of atmospheric VOCs, thereby reducing ozone production.

[Pollution Characteristics and Ozone Formation Potential of Ambient Volatile Organic Compounds(VOCs)in Summer and Autumn in Different Functional Zones of Lianyungang, China]

Atmospheric volatile organic compounds (VOCs) were collected from different functional zones of Lianyungang during the summer and autumn of 2018. One-hundred-seven VOCs species were measured by cryogenic pre-concentration and gas chromatography-mass spectrometry (GC/MS). The ozone generation potential (OFP) of VOCs was estimated by maximum incremental reactivity (MIR). Results showed that the average volume fraction of VOCs was (22.1±13.1)×10^-9. Alkanes and alkenes from C2-C4 as well as acetone and ethyl acetate were the predominant species, accounting for 59.8%-75.8% of TVOCs. The mean volume fraction in the industrial zone was the largest[(28.4±13.5)×10^-9], followed by the scenic zone[(21.7±4.4)×10^-9] and the traffic and residential mixed zone[(20.8±7.2)×10^-9]. The concentration of VOCs in autumn was significantly higher than that in summer. The industrial zone was the site with the highest volume fraction in autumn (35.4×10^-9), while the scenic zone had the highest volume fraction in summer (21.5×10^-9). Alkane, sulfur, or oxygen containing compounds and halogenated hydrocarbons were the predominant components of VOCs, accounting for 35.3%, 26.9%, and 15.6% of the total amount, respectively. Due to industrial emissions, the content of sulfur or oxygen containing compounds in the industrial zone was significantly higher than that in scenic zone and the traffic and residential mixed zone. The average ratio of T/B (toluene/benzene) indicated that vehicle and solvent use were the main sources of VOCs in the urban area. The highest OFP was found in the industrial zone, followed by the traffic and residential mixed zone and the scenic zone. Alkenes and aromatics were the largest contributors to OFP.

[Emission Status and Standards of Volatile Organic Compounds from Chinese and Foreign Bulk Petroleum Terminals]

Chinese emission standard of air pollutants for bulk gasoline terminals (GB 20950-2007) stipulate standards for vapor emissions during gasoline storage and receiving in bulk gasoline terminals. However, the standards are not applicable to crude oil, aviation kerosene, naphtha, and other kinds of oil. We assess emission standards or directives for vapor processing equipment in terminals in the United States (US) and European Union (EU), and analyze the emission status of vapor processing equipment in three typical cities in China. We further propose revisions to GB 20950-2007. We made the following observations. ① US and EU standards include scope not only for gasoline, but also crude oil and other organic liquids. ② The emission limits of non-methane hydrocarbons defined in GB 20950-2007 are i) 0.5, 1.8, and 8.9 times those defined in Subpart XX, Subpart R, and Subpart Y in the US federal regulations, ii) 1.8 and 3.1 times those defined in Rule 462 and Rule 1142 in southern California law, and iii) 0.7 and 500 times those defined in EU and German directives, respectively. The vapor leakage limit for general areas of China is 0.5 times that defined in Subpart XX of the US standards, whereas the limits for some other specific areas of China, are 0.7 and 2.0 times those defined by Rule 462 and Rule 1142 in southern California law. ③ The numerical range of P5th-P95th of NMHC emissions from the inlet and outlet of vapor processing equipment in three typical cities of China were 115-811 g·m^-3 and 0.1-20.0 g·m^-3, respectively. The proportion of NMHC emission concentrations less than or equal to 10 g·m^-3 at the outlet of vapor processing equipment was>85%. We suggest that the scope of application of GB 20950-2007 should be extended to crude oil, gasoline (including ethanol gasoline), aviation kerosene, and naphtha. The emission concentration limit of NMHC from vapor processing equipment should be tighten from 25 g·m^-3 to 20 g·m^-3, with a emission limit of 10 g·m^-3 added for particular cases.

[Concentration Levels and Impact Factors of Benzene Series in Chinese Residential Building]

From December 2016 to December 2017, the concentrations of the benzene series (benzene, toluene, xylene, and ethyl-benzene) in air were analyzed in 223 residential buildings in five climatic regions of China during different seasons. The arithmetic average concentrations of benzene, toluene, xylene, and ethyl-benzene were 6.78, 17.4, 17.68, and 9.87 μg·m^-3, respectively. Indoor benzene series concentrations in China were slightly higher than that in other countries; the standard limits for indoor benzene series concentrations in China are much higher than those of other countries and organizations. Among the many factors affecting the concentration of the benzene series in the rooms, the relationship between the completion time of decoration, smoking, and cooking frequency and the concentration of benzene homologues was studied. The results showed that the concentration of toluene decreased with the prolongation of decoration time, the concentration of benzene in smoking households was higher than that in non-smoking families, and there was no direct correlation between cooking frequency and indoor concentration of the benzene series. The study provides statistical data on exposure to the benzene series in decorated homes and a discussion of setting values of relevant standards.

[Source Profiles of Volatile Organic Compounds (VOCs) from Typical Solvent-based Industries in Beijing]

Based on the demand for a volatile organic compounds (VOCs) emissions inventory for Beijing and for the reduction in VOC emissions, the three major solvent-based industries of automobile manufacturing, furniture manufacturing, and publication printing were selected for this study. In each case, emissions link negative pressure sampling was used in combination with laboratory-based GC-MS/FID to obtain the VOC spectra. The results show that there are significant differences in the emission of VOCs from the main stages of automobile manufacturing. Specifically, the paint-coating process was dominated by the emission of oxygenated VOCs and aromatic hydrocarbons, accounting for 71.26% and 27.14% of total VOC emissions, respectively. The proportion of aromatic hydrocarbons emitted during the varnishing process was very large (84.10%), which were mainly composed of the benzene series. The differences in VOC emissions during different stages of the furniture manufacturing process were small, mainly consisting of oxygenated VOCs and aromatic hydrocarbons, which accounted for 55.08% and 18.98% of the total, respectively. Of these, alcohols and esters were the main components. VOCs emitted from different stages of the publication printing process could not be monitored separately. Thus, the VOCs in the mixed exhaust gas from this process were mainly composed of alkanes and oxygenated VOCs, which accounted for 47.29% and 44.57% of the total emissions, respectively.

[Pollution Characteristics and Emission Coefficients for Volatile Organic Compounds from the Synthetic Leather Industry in Zhejiang Province]

Based on the survey of 175 synthetic leather enterprises in Zhejiang Province, China, in 2014, this paper analyzes the control of volatile organic compounds (VOCs) and, ultimately, screened 161 key enterprises for further research. The results showed that most enterprises take measures to control waste gas; however, there is a distinct problem with the efficiency of exhaust gas collection. The industry used Solvent-based materials. The main VOC pollutants were DMF, toluene, methyl acetate, acetone, ethylacetate, and butanone. The VOC emission coefficient of the synthetic leather industry in Zhejiang was 0.168 kg·m^-2. The industry includes polyurethane and polyvinyl chloride processes, for which VOC emission coefficients were 0.170 kg·m^-2 and 0.142 kg·m^-2, respectively. In addition, the emission coefficient of polyurethane wet processes was 0.191 kg·m^-2 and that of dry processes was 0.179 kg·m^-2. The emission coefficient for VOCs in post-treatment processes was 0.120 kg·m^-2.