Heat and continental transport shape the variability of volatile organic compounds in the Eastern Mediterranean: Insights from multi-year observations and regional modeling

Abstract. Volatile organic compounds (VOCs) are key precursors in tropospheric ozone formation and secondary organic aerosol formation, thereby influencing regional air quality and climate. This study investigates the seasonal, diurnal, and temperature-driven variability of VOCs at a rural background site in Cyprus, located in the Eastern Mediterranean. VOC measurements (April 2022–June 2024) conducted with a proton transfer reaction time-of-flight Mass spectrometer (PTR-ToF-MS), along with HYSPLIT airmass back-trajectory analysis and WRF-Chem atmospheric chemistry simulations. Seventy-six VOCs were quantified and categorized into classes such as oxygenated VOCs (OVOCs), aliphatic hydrocarbons, aromatic hydrocarbons, terpenes, and nitrogen- and sulfur-containing compounds. Most VOCs exhibited distinct diurnal cycles, observed highest during 08:00–14:00 UTC due to photochemical activity and temperature-driven emissions. Biogenic VOCs, particularly isoprene, peaked in summer within the 35–38 °C range but declined under extreme heat, suggesting emission suppression from thermal stress. Monoterpenes showed elevated levels both day and night, reflecting contributions from biogenic and anthropogenic sources. Dimethyl sulphide (DMS) increased during warmer months, indicating enhanced marine microbial activity. OVOCs displayed strong seasonal and thermal enhancement during hot, dry summers due to both primary emissions and secondary formation. Benzene rose above 35 °C from evaporative and potential stress-related biogenic sources, whereas toluene and xylene were higher in colder months, linked to combustion processes. While WRF-Chem captured seasonal trends, most VOCs were underestimated, highlighting missing emission sources and oxidation pathways. Overall, the study emphasizes temperature and regional transport as key drivers of VOC variability in the Eastern Mediterranean.