Characteristics and Source Apportionment of Summertime Volatile Organic Compounds in a Fast Developing City in the Yangtze River Delta, China

Abstract

Volatile organic compounds (VOCs) are crucial for ozone formation in the Yangtze River Delta (YRD) in China. The characteristics of ambient VOCs in Nantong, a fast developing city in the YRD, were studied. Sixty ambient air samples were taken at five sites in three sampling days during summer time. One hundred and five VOCs were measured, showing that VOC concentration varied between 27.5 ppbv to 33.1 ppbv at five sites; these levels were generally lower than those for some big Chinese cities like Beijing, Shanghai and Nanjing. With larger fractions of alkanes, the Zilang (ZL) and Sanqu (SQ) sites had relatively higher VOC concentrations among the five sites. The oxidation formation potential (OFP) and secondary aerosol formation potential (SOAFP) were estimated to be 125 μg/m3 and 0.76 μg/m3, respectively. These two values were smaller than those in other big cities, as they were dominated by aromatic compounds (e.g., toluene and benzene) of which concentrations in Nantong were found to be lower. The highest toluene concentration was measured in ZL, implying substantial effects of surface coating industry near the site. Through the Positive Matrix Factorization (PMF) model, the identified sources of VOCs included LPG (Liquefied petroleum gas) combustion (13.9%), chemical industry (8.5%), natural gas use (15.6%), gasoline evaporation (12.8%), petrol industry use (11.8%), solvent use (16.2%) vehicle exhausts (12.1%) and surface coating (9.2%). A relatively small contribution from vehicles was found in Nantong compared with other big cities. Moreover, LPG emissions were identified to be relatively important in Nantong, indicated by the large mass fraction of propane and ethane concentrations in the atmosphere.