Spatiotemporal variability of benzene in a petrochemical industrial complex: insights from repeated mobile SIFT-MS monitoring and comparison with Me-DOAS.

This study investigated the spatiotemporal characteristics of benzene concentrations in a petrochemical industrial complex using integrated mobile monitoring techniques. Real-time measurements were conducted using vehicle-mounted Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS), with Mobile-extraction Differential Optical Absorption Spectroscopy (Me-DOAS) applied as a complementary approach to assess spatial consistency and seasonal patterns. Benzene concentrations showed clear seasonal and diurnal variability, with higher levels and more frequent high-concentration events in winter and consistently elevated concentrations during nighttime (22:00-03:00) under stable atmospheric conditions. Spatial analysis revealed that exceedance events were concentrated within specific industrial blocks associated with benzene-handling and emission-intensive processes, indicating persistent localized hotspots. Although absolute concentration levels differed between SIFT-MS and Me-DOAS, both techniques reproduced consistent temporal patterns. Agreement was weak under background conditions but strengthened during high-concentration events, suggesting convergence under source-dominated conditions. Me-DOAS effectively represents spatially averaged concentrations, whereas SIFT-MS captures short-term variability and localized high-concentration events. Overall, the results demonstrate that high-resolution mobile monitoring can resolve short-term benzene peaks and identify spatially persistent hotspots, providing practical information for targeted air quality management.