A recent study has revealed that winter ozone (O3) pollution, which can severely affect human health, may be driven by alkene emissions from local petrochemical industries.
This discovery has highlighted the need for targeted actions in industrial regions to combat this alarming environmental issue.
The study, conducted by researchers from the Hong Kong Polytechnic University, focused on wintertime ozone pollution in Lanzhou, China, a city traditionally associated with heavy industrial activity.
Ozone pollution is typically linked to warm weather and strong solar radiation, but the study found a worrying trend of high O3 concentrations during the colder winter months, especially in January 2018.
Ozone levels during these days exceeded 100 parts per billion (ppbv) and even peaked at 121 ppbv, far beyond the typical levels seen in warmer conditions.
Traditionally, the presence of ozone is understood to be driven by strong sunlight and the associated photochemical reactions. However, the research found that the high winter ozone levels in Lanzhou did not follow this typical pattern.
Instead, the study highlighted the role of alkene ozonolysis, a chemical reaction that occurs without sunlight, as a significant contributor to the formation of O3.
This process involves alkenes reacting with ozone to produce intermediate compounds, which quickly generate reactive radicals. These radicals, in turn, accelerate the formation of ozone, particularly during winter months when sunlight is minimal.
Using an advanced photochemical box model, the researchers were able to simulate and study this phenomenon.
Their findings showed that alkene ozonolysis was the dominant driver of ozone formation in Lanzhou's winter pollution, contrary to the conventional understanding that photolysis-driven radical sources were the main contributors.
The study concluded that alkenes contributed to nearly 90% of the ozone formation during the observed episodes, underscoring the importance of regulating these chemicals in petrochemical industries.
The researchers identified two specific alkene species, trans/cis-2-butene and propene, as major contributors to this wintertime ozone pollution.
These compounds are commonly released by petrochemical industries, and their presence in the atmosphere plays a crucial role in the formation of harmful ozone levels.
The study recommends that mitigation strategies focus on reducing the levels of these alkenes and nitrogen oxides. For instance, cutting alkene levels by 28.6% or nitrogen oxides by 27.7% during the early afternoon hours could significantly lower ozone concentrations.
The findings of this study challenge existing views on ozone pollution, revealing that it is not only a problem during hot, sunny weather but can also occur in cold, low-light conditions.
As the authors Jin Yang and Yangzong Zeren noted, their research provides important insights into how ozone formation can be more complex than previously understood, especially in industrial areas.
They called for targeted actions to address alkene emissions in such regions to prevent further pollution and protect public health.
Long-term exposure to high levels of ozone can have serious health consequences, particularly for the respiratory system. Prolonged exposure to ozone pollution can cause irritation and inflammation of the airways, leading to symptoms such as coughing, chest tightness, and worsening asthma.
In severe cases, it can also damage lung tissues, further highlighting the need for urgent action to reduce ozone levels in industrial areas like Lanzhou.
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