Snow can accumulate pollutants from urban air and help researchers study the scale of winter contamination, but the apparent freshness of the air after a snowfall does not mean harmful particles have disappeared. Anna Kurbatova, head of the closed-cycle economy department at the Institute of Ecology of RUDN University and a candidate of biological sciences, explained how snow washes aerosols out of the atmosphere, why a sense of clean air after snowfall is not proof of air quality, and how snow-monitoring data should be interpreted. According to the expert, snow cover serves as a natural accumulator of pollutants and an indicator of urban air conditions for environmental scientists, but it cannot be assessed by visual impressions alone.
Key Takeaways: Snowflakes capture suspended particles and carry them to the ground, making snowfall one of the atmosphere’s self-cleaning mechanisms. About 95% of a snowflake is air, and its branched, porous structure creates a large contact surface for pollutants. A 2024 study in Science of the Total Environment examined six snowfalls in northwestern Spain; in some cases particle concentrations fell sharply during the first 30 minutes, while in others pollution barely decreased.
The atmosphere always contains aerosols — tiny solid and liquid particles suspended in air. Some are natural, including soil dust, sea salts, wildfire smoke and biological particles. In cities, they are joined by emissions from transport, industrial facilities and heating systems, as well as dust produced by wear on asphalt and vehicle tires. These anthropogenic sources largely shape winter pollution levels, while snow acts as a temporary natural filter that holds part of the contamination.
A snowflake’s complex, branched shape and porous structure give it a much larger contact area with air than a smooth raindrop. As snowflakes fall, they collide with aerosol particles and capture them; atmospheric physics specialists describe this as the removal of impurities from the air through precipitation. How effectively this process works depends on particle size, snowflake characteristics, snowfall intensity, humidity and weather conditions. As a result, a snowfall of similar intensity can produce different outcomes depending on the meteorological situation and the mix of emissions.
Kurbatova cautions that snow-monitoring data require careful interpretation: the composition of pollutants in snow cover can be a valuable source of information about urban air, but such data should not be reduced to a single observation. She explains that the feeling of “freshness” after a snowfall is often linked to visual clarity and a reduction in odors, while the chemical composition of the air may remain hazardous. Although particle concentrations sometimes drop noticeably in the first half hour, new emissions can worsen air quality again in the following period.
In the coming winter season, environmental specialists and city services should regularly analyze snow samples, identify pollution sources and provide residents with reliable information about air quality. The cleaning effect of snowfall should be assessed not by subjective impressions but by data from monitoring stations and laboratory tests. Such an approach would help forecast winter pollution episodes in advance and plan infrastructure, environmental and public-health measures in a timely manner.
Source: kun.uz