Compilation of emission inventory and source profile database for volatile organic compounds: A case study for Sichuan, China

The purpose of this paper is to develop an emission inventory and source profile database for volatile organic compounds (VOCs) in Sichuan Province. Based on the test data of the research literatures, the source profiles of species containing no oxygenated volatile organic compounds (OVOCs) were revised and reconstructed to obtain the normalized VOCs source profile. In addition, the source profile-based 1 km x 1 km speciated VOCs emission inventory was established in accordance with the 2015 Air Pollution Source Emission Inventory in Sichuan Province with the ozone formation potential (OFP) estimated to assess the impact on ozone formation. There were 45 profiles and 519 species included in the established VOCs source profile database. Since the profiles were established mainly based on domestic test data, foreign research results were employed to supplement the profiles of some sources that had not been actually tested or had been researched less in China. In addition, the profiles of some sources such as biomass burning and transportation with emissions containing rich OVOCS have been revised and reconstructed, and the profiles including redundant data of many tested sources were simplified accordingly as well. Therefore, the established source profile database is well applicable to the establishment of the speciated VOCs emission inventory and the source apportionment. The VOCs emission inventory showed that the anthropogenic emissions of alkanes, alkenes, alkynes, aromatics, OVOCs, halohydrocarbons and other VOCs in Sichuan Province were 167.1 kt, 77.4 kt, 13.2 kt, 216.7 kt, 202.7 kt, 32.5 kt and 64.2 kt respectively; the total OFP in Sichuan was 2584.9 kt, and the above-mentioned VOCs contributed 6.9%, 26.1%, 0.5%, 42.3%, 23.2%, 0.4% and 0.5% to the total OFP, respectively. Therefore, alkenes, aromatics and OVOCs were the major species for ozone formation among the VOCs emitted in Sichuan Province, and controlling the emissions of such species plays a key role in reducing ozone formation. The major VOCs species emitted in various cities of Sichuan Province were aromatics, OVOCs and alkanes; however, different cities have their own remarkable characteristics. VOCs emissions and major OFP contributing species in Sichuan Province were mainly distributed in the Sichuan Basin as well as some areas in Liangshan and Panzhihua, where the population was relatively dense and the industry was relatively developed. The main source of m-Xylene and toluene was solvent use; therefore, m-Xylene and toluene were more intensively distributed in urban built-up areas. Furthermore, since biomass burning contributed a lot to ethene and formaldehyde emissions, ethene and formaldehyde were substantially distributed in cultivated areas in eastern Sichuan and southern Sichuan.