Geospatial assessment of agricultural lands critical to air quality on the Columbia Plateau, Washington State

ABSTRACT:

The soils and landscape of the Columbia Plateau in eastern Washington and northeastern Oregon have developed primarily as a result of redistribution of glacial outwash sediments by wind. Contemporary agricultural disturbance of regional soils facilitates wind erosion that impairs downwind air quality by the introduction into the atmosphere of large quantities of particulate aerosols less than 10 microns in aerodynamic diameter (PM₁₀). Reducing these agricultural contributions to PM₁₀ concentrations in urban areas has been identified as a critical component of regional compliance under the Clean Air Act. We designed a sampling and analysis scheme to develop empirical relationships first between total mass flux during wind tunnel erosion trials and soil aggregate size distributions; and second between soil PM₁₀ emission potentials and primary particle size distributions. We then applied those empirical relationships to predict potential total soil erodibility and potential PM₁₀ emissions at a larger set of field soil sample sites. The resultant point predictions were interpolated spatially using geostatistical methods to generate a prediction map of PM₁₀ emissions hazard, which is similar to the U.S. Department of Agriculture (USDA) Farm Services Agency map of air quality conservation priority areas for the Columbia Plateau.