SECONDARY ORGANIC AEROSOL AND OZONE FORMATION POTENTIALS FROM DIESEL ENGINE EMISSIONS AT ISALE-KOTO, ILORIN KWARA STATE, NIGERIA

Secondary organic aerosols (SOAs) and tropospheric ozone (O₃) pose significant risks to air quality and public health in urban environments, particularly in developing regions reliant on diesel-powered machinery.

This study investigates aromatic volatile organic compounds (VOCs) benzene, toluene, ethylbenzene, and xylene isomers (BTEX) emitted from diesel grinding engines in the Isale-Koto food processing market, Ilorin, Nigeria. Passive sampling at ten locations (five indoor, five outdoor) over one month captured VOC concentrations, analyzed via gas chromatography. Ozone formation potential (OFP) was estimated using maximum incremental reactivity (MIR) coefficients, while secondary organic aerosol potential (SOAP) employed reactivity-based metrics relative to toluene.

Results revealed higher indoor VOC levels, with total OFP at 148.014 µgm-³indoors versus 128.098 µgm-³outdoors (15.5% increase), dominated by toluene (29-31%) and m-xylene (25%). total SOAP at 4,076.82  µgm-³ (16.4% above outdoor levels). Toluene, m-xylene, and ethylbenzene were dominant contributors to OFP, while benzene, toluene, and ethylbenzene accounted for 84% of SOAP due to high concentrations and reaction. These findings highlight diesel engine exhausts as a key precursor source to ozone and SOA formation with indoor accumulation due to poor ventilation amplifying photochemical pollution for ground-level, posing serious health risks especially for workers exposed over long durations. The study emphasizes on the urgent need for improved ventilation, cleaner energy alternatives, and emission regulations