Mobile monitoring of VOCs and source identification using two direct-inlet MSs in a large fine and petroleum chemical industrial park

Mobile monitoring with direct-inlet MS (DI-MS), one of the most direct and effective ways to track emission sources, can effectively serve air quality management in chemical industrial parks (CIPs). Mobile monitoring using a high mass-resolution proton-transfer-reaction time-of-flight MS (HMR-PTR-TOFMS) and single-photon ionization time-of-flight MS (SPI-TOFMS) was conducted in a large fine and petroleum CIP in eastern China for three days. The high mixing ratios of aliphatic hydrocarbons (AHs), aromatics, oxygenated VOCs (OVOCs), and nitrogenous VOCs (NVOCs) were found in the northeast, middle, north, and northeast of the fine chemical industrial zone (FCIZ), respectively. OVOCs were the most abundant VOC group in this area. Abnormal emissions of aromatics were universal throughout the CIP. We discovered 38 characteristic VOCs by the HMR-PTR-TOFMS, mainly including C6-C10 aromatics, C2-C6 carbonyls, C2-C3 organic acids, and some NVOCs. The time series and spatial distribution of the TVOCs obtained by the two DI-MSs are generally consistent. A comparison of the speciated VOCs at the TVOC peak points illustrates that the characteristic VOCs obtained by different instruments differed significantly: PTR-TOFMS showed an advantage in measuring aromatics and OVOCs; SPI-TOFMS showed an advantage in measuring aromatics and some Ahs; offline GC-MS showed an advantage in measuring AHs, aromatics, some OVOCs, and halohydrocarbons. Similarities were compared between five positive matrix factorization (PMF) model-based fingerprints of VOCs in a previous study and observed profiles of VOCs from mobile monitoring. The emission sources of the five fingerprints were identified and validated: two were widely distributed, one was a chemical reagent production factory, one was an acrylic fiber production plant, and one was a pesticide factory. This study demonstrated methods for analyzing mobile monitoring data, characterizing the VOCs in the fine and petroleum CIP, correlating the results of stationary observation and mobile monitoring, and integrating the source tracing system with DI-MSs.