"Our finding was not formerly recognised and leads to a different understanding of how snowpack-chemistry functions," Harry Beine of Caltech and the Istituto Inquinamento Atmosferico told environmentalresearchweb. "It is, however, the result of a fairly limited experiment in the lab."
Beine and colleagues obtained their result by illuminating natural snow in Caltech's Geology and Planetary Sciences cold-room laboratory at –25°C. The snow was sampled at the end of the winter season after it had been exposed to natural, intense sunlight. The researchers measured the reactive-trace gases that were released from the snow surface both in the dark and when the sample was illuminated.
The team found that humic substances within or at the surface of the snowpack significantly enhanced the production of HONO (gaseous nitrous acid) both in the dark and under light. Indeed, these substances may be an essential prerequisite for snow to release this pollutant. They are major constituents of soil organic matter (humus) that contribute to soil chemistry and quality; they are also precursors of some fossil fuels and can be found in peat, coal and in many upland streams, lakes and oceans.
HONO is an inorganic acid that is fairly bad for your lungs and eyes, explains Beine. It also affects buildings and is a major problem during smog episodes in cities. It builds up overnight and then reacts to sunlight. Although a "bad" pollutant in its own right, it also acts as an intermediate to a series of other pollutants.
In the remote polar environment, HONO should not be present but it is released from snow and plays an important role in the recycling of trace chemicals. In these cold environments it is not dangerous because health effects only set in at much higher concentrations.
"The findings are a piece in the puzzle to understand how snow surfaces alter and interact with the overlying atmosphere in polar, high-alpine and seasonally snow-covered regions," said Beine. "The intuitive feeling that many people have is that snow makes the air smell fresh and clean. There are chemical reasons for this perception: snow surfaces release a host of reactive trace chemicals (such as HOOH, NOx, HONO, CH2O and halogens), which in turn produce OH, O3 and other species, which have the ability to clean the atmosphere."
The next stage for Beine and colleagues' research is the Barrow 2009 experiment that the OASIS (Ocean-Atmosphere-Sea-Ice-Snowpack Interactions) programme is currently organising. "Around 35 scientists will come together from February to April to explore snow-atmosphere interactions at this location," revealed Beine. The work was published in Environmental Research Letters.