Despite efforts to reduce emissions and strengthen environmental protections, ground-level ozone and particulate matter pollution levels in Los Angeles remain stable.

Controversial research

This confusing situation led scientists from Colorado and South Korea to identify “secondary” sources of pollution as a significant factor in 2022. Based on this, a recent multi-institutional study suggests that: trees and shrubs can contribute significantly to pollution.

The study, published in the journal Science, terpenoids – organic compounds in plant matter that often act as antioxidants. When released into the atmosphere, terpenoids turn into volatile organic compounds (VOCs), which react with existing pollutants to form harmful ozone and fine particles.

Results

The research was conducted by scientists from Germany, the California Institute of Technology in Berkeley, Colorado, and the National Oceanic and Atmospheric Administration. In June 2021, they flew a drone equipped with a mass spectrometer over Los Angeles to measure the concentration of volatile organic compounds.

They combined these measurements with 3D wind speed data to track the origin of the pollutants. The results showed terpenoids are the main source of VOCs, especially in areas rich in vegetation and on hot daysTemperatures above 30 degrees Celsius have increased emissions even in densely populated, less vegetated areas like downtown Los Angeles.

The study also noted that higher temperatures increased anthropogenic VOC pollution from sources such as gasoline and personal care products. Cosmetics had a small but noticeable impact on smog in densely populated areas, according to lead author Eva Pfannerstil of the Jülich Research Center in Germany.

The researchers emphasize that their findings must be understood in context. “Although it is difficult to control factory emissions, it is even more important to control them” [антропогенну] part,” Pfannerstill noted.

Science editor Jesse Smith echoed this view, noting that reducing urban air pollution must account for changes in emissions caused by climate warming.