Ozone–VOC Relationship Analysis in Urban Environments of the Middle East

Analyzing volatile organic compounds (VOCs) and ozone (O3) relationships (VOC–O3) in Middle Eastern cities is essential for understanding air pollution, as VOCs act as primary precursors for ozone formation under intense solar radiation and high temperatures. In this study, VOCsO3 have been investigated at six cities in the Middle East: three in Saudi Arabia (Abha, Riyadh, and Dammam), one in Egypt (Cairo), one in the United Arab Emirates (Dubai), and one in Iran (Isfahan). The methodology of this work includes examining and calculating annual, seasonal, and monthly averages of ten VOCs Ethylene (C2H4), Ethanol (C2H5OH), Ethane (C2H6), Propylene (C3H6), Propane (C3H8), Formaldehyde (CH2O), Acetaldehyde (CH3CHO), Acetone (CH3COCH3), Methanol (CH3OH), and Toluene (for MACCity emission inventory dataset) and O3 (for MACC dataset) and their relationships over the 1960–2020 study period. Preliminary analysis indicates that the large regional variations in VOC–O3 dynamics are due to differences in emission source locations, photochemical activity, and meteorological factors; it also indicates that all correlations are positive. The VOC–O3 correlation showed significant correlations in Abha, ranging from 0.51 to 0.61, peaking with CH3CHO (0.61). Correlation values varied in Dammam, reaching 0.58 for both C2H5OH and CH3OH, and 0.53 for CH3CHO. While certain reactive VOCs are associated with O3 formation, the relationships are complex and location-specific. Our findings show that in Abha, oxygenated VOCs (especially CH₃CHO) dominate O₃ formation, while in Dammam, despite high total VOC emissions, lower-than-expected O₃ production suggests NOₓ-limited conditions. This highlights the need for city-specific, compound-specific control strategies.