A recent study has revealed that severe wintertime ozone (O3) pollution, typically associated with warm weather, is being driven by alkene emissions from local petrochemical industries in Lanzhou, China. Researchers from the Hong Kong Polytechnic University discovered alarming O3 levels in the cold winter months of January 2018, with concentrations exceeding 100 parts per billion (ppbv) and peaking at an alarming 121 ppbv. This is contrary to the traditional belief that O3 pollution mainly occurs during hot weather with strong solar radiation.

The team used an advanced photochemical box model to simulate photochemical smog at the urban scale, identifying alkene ozonolysis as the main contributor to O3 formation. Unlike the typical radical sources initiated by sunlight, the alkene reaction occurs without sunlight and produces reactive radicals that accelerate O3 production. Alkenes, particularly trans/cis-2-butene and propene, contributed to nearly 90% of the O3 levels during the pollution episodes.

The study highlights the need for targeted mitigation strategies, suggesting that reducing alkene levels by 28.6% or nitrogen oxides by 27.7% during early afternoon hours could significantly reduce O3 levels. The authors stressed the importance of taking action in industrial regions to reduce these harmful emissions.

Long-term exposure to high O3 levels can damage respiratory tissues, causing inflammation, irritation, and exacerbating asthma symptoms, posing serious health risks to the local population.