Threshold Velocity of Agricultural Soils within the Columbia Plateau, USA.

Wind erosion causes loss of soil productivity, degradation of air quality, poor visibility, and changes to climate as a result of modifying the Earth's radiation balance. Fine airborne particles with mean aerodynamic diameters less than 10 and 2.5 microns are stringently regulated by the US Environmental Protection Agency (USEPA) as criteria pollutants. Wind erosion and particulate emissions from agricultural lands are a concern within the Columbia Plateau because communities have failed to comply with USEPA air quality standards. To aid in developing predictive tools and mitigation strategies for windblown dust emissions in the region, the objective of this study was to determine the threshold friction velocity (friction velocity required to initiate soil movement) of major soil types found across the Columbia Plateau. Samples from the upper 3 cm of the soil profile were collected at five locations representing different soil types across the region. The samples were screened to remove debris and nonerodible aggregates and air dried at 30C. The samples were placed in a shallow pan and then subject to a range of wind velocities using a Sensit and aerosol samplers (DustTrak and E-samplers) installed at heights of 0.5 to 10 cm above the soil surface. Threshold friction velocity was defined by the onset of particulate emissions as recorded by the various instruments. Although some variation was found in threshold friction velocity, the majority of soil types had a similar threshold velocity.

Key words: dust, wind erosion, PM10