Solluble Dust Emissions from Salt Efflorescence Crusted Soil Surfaces

Many semi-arid and arid areas of the Earth have internal drainage features that have resulted in salt water accumulation. Recent droughts and rising temperatures are causing these saltwater bodies to dry and shrink, leaving a surface of salt evaporites. Areas near the original shoreline may be bombarded by blowing sand and fugitive dust emissions are common from these locations. This dust, especially the soluble components, poses human and environmental health hazards. We created single salt efflorescences on soil pans by wetting the soil from the bottom with salt solutions and allowing natural drying at he surface. These pans were subsequently placed in a suction-type wind tunnel with a centerline velocity of 12 m s-1 and abraded with washed 40 mesh sand for a period of 20 minutes. Emissions from the soil pans were aspirated through a riffled transfer section that trapped coarse sediments including most of the abrader sand, into a 0.3 m3 settling chamber to trap medium sediments, and finally through quartz fiber filters to trap fine sediments capable of long-range transport and inhalation. We found that most of the efflorescences resulted in less total dust emission than untreated soil surfaces but that many had greater soluble salt emissions. As salt lakes continue to dry and shrink, surface management should be employed to limit dust emissions.