LAUSR

In the area of a petrochemical industrial site, ten monitoring stations are established to determine the airborne pollutants that are emitted, which include criteria air pollutants and 54 species of ozone formation precursors of volatile organic compounds (VOCs). The hourly pollutants are increased by human activities, such as traffic flow after 7:00 a.m., and ozone becomes more abundant as solar radiation increases in intensity. Monthly air pollutants are present in low concentrations during the rainy season from May to September and in high concentrations from October to April. Results show that VOC concentrations are low in the summer (average concentration 5.7–5.9 ppb) and more than double in the winter (11–12 ppb), with 52–63% alkanes, 18–24% aromatics, 11–22% alkenes and 4.7–7.1% alkynes. Ethane, toluene, propane, n-butane, ethylene and acetylene are the major VOCs, with an annual average concentration exceeding 0.50 ppb. In 2016–2020, the VOC concentration is decreased from 10.1 to 7.73 ppb, corresponding to the ozone formation potential (OFP) decrease from 84 to 61 μg-O3 m−3, with toluene, m,p-xylene, ethylene and propene being the most abundant species. The primary VOC sources are petrochemical industry sites, fuel combustion, vehicle exhaust emissions and evaporation, solvent application, industrial facilities and emission from farming vegetation.