Melting snow is riddled with pollutants

Posted Apr 9, 2017 by Tim Sandle
The big thaw is underway in the northern hemisphere as snow in snow bound areas melts away. Melting snow does not only release water. A new study has found urban snow accumulates a toxic cocktail from car emissions.
Snow continues to fall late Wednesday afternoon as the winter storm hitting Southwestern Ontario con...
Snow continues to fall late Wednesday afternoon as the winter storm hitting Southwestern Ontario continues into the evening hours.
The finding comes from a study undertaken between McGill University and École de technologie supérieure in Montreal. According to lead investigator Dr. Yevgen Nazarenko the results are alarming: “We found that snow absorbs certain polycyclic aromatic hydrocarbons which are organic pollutants known to be toxic and carcinogenic.”
What is important to the researchers in understanding how the pollutants interact with the environment. While snow appears clean it can contain many different contaminants such as toxins, heavy metals, viruses and bacteria. With one pollutant in particular, snow absorbs chemicals from car exhausts, such as benzene, ethylbenzene, toluene, and xylenes.
The presence of these pollutants can be detected, to a degree, by the human nose according to Dr. Nazarenko. He contrasts the smell of fresh now (a clean, crisp sensation) with that of melting smell, where the chemical pollutants become more noticeable.
To add a degree of scientific quantification to this olfactory stimulation, the researchers provided data relating to how snow absorbs pollutants. This was shown in a laboratory by exposing snow to engine exhaust in a frozen glass sphere. This study demonstrated that exhaust emissions affect the snow, but there were differences based on the type of fuel injection in the engine.
In addition the research looked at meteorological factors. Here it was found that colder temperatures and interaction with snow increased the relative presence of smaller nanoparticles in the polluted air above the snow. These particles are among the most serious in terms of the effect on human health.
The research also focused on chemical reactions. Here it was noted that as pollutants are absorbed into the snow crystals some chemicals undergo transformations. This process can lead to additional pollutants with different levels of toxicity and carcinogenicity. Many of these are later released with meltwater.
The researchers put forward their findings as a trigger for further study and they highlight a new area of environmental concern. The research has been published in the journal Environmental Pollution. The study is titled “Role of snow in the fate of gaseous and particulate exhaust pollutants from gasoline-powered vehicles.”