(Photo taken by Xianming in a snow storm on 01/24/2015)
Snow, as rain, is a form of precipitation in the water cycle of the earth. Different from rain, snow is a more efficient scavenger of a variety of contaminants from the atmosphere. These contaminants include salts and salt additives, heavy metals, asbestos, petroleum products such as oil and grease nutrients, bacteria, organic chemicals such as pesticides and PCBs in the air due to its high specific surface area.
After precipitation, snow on the ground acts as a temporary storage of contaminants during sometimes month-long periods. As such, snow functions as a non-point source of pollution during snow melt. Snow melt generally occurs during a short time period, during which the concentration of contaminants in surface runoff and in receiving waters tend to increase.
Influenced by the properties of the contaminants captured by snow, the pollutants with high water solubility are released with the initial meltwater fractions and the particulate pollutants at the end of the snowmelt. The levels of metals, suspended solids and organic contaminants may be several orders of magnitude higher than pollutant loads in rain-induced runoff. Such peak of contaminant concentrations would have a huge impact on the ecosystems.
Therefore, disposing of snow may cause degradation to the water resources. Land disposal is generally preferred since sediments and litter can be collected, some metals can be filtered out by the underlying soils, and meltwaters can either evaporate or enter a surface water gradually thereby diluting and biodegrading the contaminants as they enter. In areas where there is significant potential for contamination of groundwater which is utilized for drinking water supply, disposal of snow into surface water bodies may be the only viable disposal alternative. However, prior to disposal, the snow should be treated for solids removal.
Snow flakes can capture chemicals that are present both in the gas phase and in the particle phase of the air
References and more information:
http://dx.doi.org/10.1016/j.atmosenv.2004.03.039
http://publications.lib.chalmers.se/records/fulltext/local_126677.pdf
https://denr.sd.gov/dfta/wp/snow.aspx
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