Land disturbances, such as agricultural practices and development, may have a big impact on snow purity and
melt rates, according to a large-scale survey of impurities in North American snow by researchers at the University of Washington. The researchers were particularly interested in the Bakken oil fields of northwest North Dakota. Before undertaking the study, they predicted that diesel emissions and air pollution associated with oil exploration would darken the snowpack, decreasing the amount of sunlight it reflects and increasing its melt rate. They found, however, that while these activities do add soot to the snow, the dirt they stir up adds an equal amount of impurities to the snowpack. Disturbances from clearing oil pads, new housing sites, agricultural activities, and extra truck traffic on unpaved roads add a significant amount of dirt to snowfields, they found.