Context:
Recently published in the journal Environmental Science and Ecotechnology, a study done by Hong Kong Polytechnic University found that severe wintertime ozone (O3) pollution in Lanzhou, China, may be driven by alkene emissions from local petrochemical industries.
- This is “contrary to the consensus that O3 pollution mainly occurs in warm weather with strong solar radiation,”.
- The team used an advanced photochemical box model to study urban-scale photochemical smog.
- Key Findings:
- Alkene ozonolysis was identified as the main cause of O3 formation, not traditional radical sources initiated by photolysis.
- Alkenes react without sunlight, producing Criegee Intermediates that generate reactive radicals (hydroxide , hydroxide radical (HO2), organic peroxy radical (RO2)), accelerating O3 production.
- Alkenes contributed to nearly 90% of O3 during pollution episodes.
- Key alkene species -Trans/cis-2-butene and propene were identified as major contributors to the pollution.
- Reducing alkene levels by 28.6% or nitrogen oxides by 27.7% in the early afternoon could significantly reduce O3 levels.
- The study shows that O3 formation can occur in cold, low-light conditions.
- Long-term ozone exposure can harm the respiratory system, causing inflammation, irritation, coughing, chest tightness, and worsening asthma.
- The researchers recommend targeted actions in industrial regions to mitigate ozone pollution.
About Ozone Pollution
- Ozone at ground level is a harmful air pollutant due to its adverse effects on both human health and the environment. It is also the primary component of “smog”.
- Ozone usually reaches unhealthy levels on hot, sunny days in urban areas, but can also be high during colder months.
- Ozone can be carried over long distances by wind, affecting even rural areas.