Long-term Observations of Volatile Organic Compounds at a Regional Background Site in the Eastern Mediterranean Affected by Middle Eastern Air Masses

Volatile Organic Compounds (VOCs) play a key role in the formation of tropospheric ozone and secondary aerosols, influencing air quality, climate, and human health. Originating from both biogenic and anthropogenic sources, their volatile nature enables long-range transport, with oxidation products impacting distant regions. The island of Cyprus, located at the intersection of Europe, Asia, and Africa, experiences complex air mass dynamics that transport diverse VOC emissions and their oxidation products, making it a key site for studying regional air quality. However, VOC observations in the Eastern Mediterranean and Middle East region (EMME) are often constrained by the short duration of measurement campaigns and a narrow focus on specific species, resulting in a significant data gap. In this study, we employed a Proton Transfer Reaction–Time-of-Flight Mass Spectrometer (PTR-ToF-MS 4000; Ionicon Analytik, Austria) to perform continuous, high-resolution measurements of VOCs from April 2022 to June 2024 at the Cyprus Atmospheric Observatory (CAO-AMX; 35.038692° N, 33.057850° E; 532 m above mean sea level). This site represents regional background concentrations while providing valuable insights into local emission sources, including significant contributions of biogenic emissions originating from the Troodos mountain forest. We analyzed over 70 VOC species, classifying them into chemical groups such as aromatics, alcohols, aldehydes, ketones, and oxygenated VOCs. By examining their distinct seasonal and diurnal variations along with the origins of the sampled air masses, we derive valuable information about their regional and local emission dynamics and their respective impact on atmospheric chemistry. Additionally, we compared the measured VOC mixing ratios with simulations from a coupled atmospheric chemistry model (WRF-Chem) to comprehensively evaluate the model’s performance and its ability to reproduce the observed VOC variability. We find that while regional biogenic sources are reasonably well captured by the simulations, significant discrepancies for oxygenated VOCs suggest the presence of uncharacterized VOC sources in the Middle East. This work offers a unique, long-term perspective on the role of VOCs in shaping air quality in the EMME region, supporting efforts to mitigate air pollution and address climate change impacts.