Quantification of Impurities in Prairie Snowpacks and Evaluation and Assessment of Snow Parameters

Recent measurements of snow impurities collected in North American prairie snowpacks show deposition of significant quantities of atmospheric aerosols and local dust into the snowpack. While concern over the effects of soot and other impurities in atmospheric samplings has been a scientific focus for decades, few efforts have been made to determine the effects of these highly absorbing impurities on snow albedo. These impurities can lower snow albedo in the visible portion of the electromagnetic spectrum by 5-15% with concentrations of only 1 part per million by weight (ppmw). Mass impurities were measured in snowpacks in Dickinson County, Iowa taken at agricultural, lake and other sites during multiple days in 2007 and 2008. The sampling captured two snowfall events in 2008 with snowfall totals exceeding 290 mm. The contaminant contributions to light absorption were determined to be primarily from agricultural dust and black carbon which are identifiable by their wavelength dependence. Impurity concentrations are determined by optical methods. Snow meltwater was filtered through a Nuclepore filter and the filters were analyzed for light absorption using the Integrating Plate (IP) method at 16 equal interval wavelengths across the visible portion of the electromagnetic spectrum. Average impurity concentrations were found to range between 15 and 80 ngC/gm. These concentrations are higher than those typically measured in the Arctic and Antarctic.