[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.

[Composition and Atmospheric Reactivity of Ambient Volatile Organic Compounds(VOCs)in the Urban Area of Nanjing, China].

Online gas chromatography with flame ionization detection (GC-FID) systems were employed to observe 56 species of volatile organic compounds (VOCs) in the environmental atmosphere in Nanjing in 2015. The results showed that the annual volume fraction of VOCs was (17.49±11.35)×10-9. The highest concentration of VOCs was in April (22.21×10-9), and the lowest in July (12.39×10-9). Diurnal values of VOCs concentration had no obvious variations. Alkanes, alkenes, aromatics, and acetylene accounted for 56.51%, 11.06%, 24.62%, and 7.81%, respectively. Propane (15.26%), ethane (14.14%), acetylene (7.81%), toluene (6.97%), n-butane (6.23%), ethylene (5.23%), isobutane (4.34%), propylene (4.13%), isoprene (4.12%), and m/p-xylene (4.06%) were the most abundant VOCs species. The average ratio of toluene/benzene (T/B) was 2.02, indicating that the atmospheric VOCs were mainly affected by emissions of motor vehicles, especially gasoline vehicles. The average ratio of ethane/ethyne (E/E) was 2.24, showing that the plume had aged. The hydroxyl radical (·OH) loss rate(L·OH) and ozone formation potential(OFP)were applied to assess the chemical reactivity of VOCs. The atmospheric activity of VOCs was higher in the winter and spring than in the summer and autumn. Aromatics and alkenes were the most important contributors to L·OH and OFP. Their contributions to L·OH and OFP were 46.96% and 41.58%, and 33.73% and 39.86%, respectively. Propylene, ethylene, and xylene were the most active species.

[Source profile and chemical reactivity of volatile organic compounds from vehicle exhaust].

Light-duty gasoline taxis (LDGT) and passenger cars (LDGV), heavy-duty diesel buses (HDDB) and trucks (HDDT), gasoline motorcycles (MC) and LPG scooters (LPGS), were selected for tailpipe volatile organic compounds (VOCs) samplings by using transient dynamometer and on road test combined with SUMMA canisters technology. The samples were tested by GC-MS to analyze the concentration and species composition of VOCs. The results indicate that light-duty gasoline automobiles have higher fractions of aromatic hydrocarbons, which account for 43.38%-44.45% of the total VOCs, the main aromatic hydrocarbons are toluene and xylenes. Heavy-duty diesel vehicles have higher fractions of alkanes, which constitute 46.86%-48.57% of the total VOCs, the main alkanes are propane, n-dodecane and n-undecane. In addition, oxy-organics account for 13.28%-15.01% of the VOCs, the main oxy-organics is acetone. The major compound from MC and LPGS exhaust is acetylene, it accounts for 39.75% and 76.67% of the total VOCs, respectively. VOCs exhaust from gasoline motorcycles and light-duty gasoline automobiles has a significantly higher chemical reactivity than those from heavy-duty diesel vehicles, which contribute 55% and 44% to the atmospheric chemical reactivity in Shanghai. The gasoline motorcycles and light-duty gasoline automobiles are the key pollution sources affecting city and region ambient oxidation, and the key active species of toluene, xylenes, propylene, and styrene make the greatest contribution.