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United States Department of Agriculture

Agricultural Research Service

Research Project: Mitigating Agricultural Sources of Particulate Matter and Greenhouse Gas Emissions in the Pacific Northwest

Location: Northwest Sustainable Agroecosystems Research

Title: Threshold friction velocity influenced by wetness of soils within the Columbia Plateau

Authors
item Sharratt, Brenton
item Vaddella, Venkata -
item Feng, Guanglong -

Submitted to: Aeolian Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2013
Publication Date: June 1, 2013
Citation: Sharratt, B.S., Vaddella, V., Feng, G. 2013. Threshold friction velocity influenced by wetness of soils within the Columbia Plateau. Aeolian Research. 9:175-182.

Interpretive Summary: Wind erosion occurs when the wind velocity exceeds the threshold wind velocity of particles lying on the soil surface. Predicting wind erosion is therefore dependent on our ability to estimate the threshold wind velocity of soils. Soil moisture is one of the most important factors affecting the threshold wind velocity, but no information exists that describes the relationship between soil moisture and threshold velocity of soils in the Columbia Plateau. We found that moisture did not influence the threshold wind velocity until the soil water potential exceeded -5 MPa for five major soils found in the region. Model developers can use the relationship developed between soil moisture and threshold wind velocity in this study to improve wind erosion model performance in the Columbia Plateau.

Technical Abstract: Windblown dust impacts air quality in the Columbia Plateau of the U.S. Pacific Northwest. Wind erosion of agricultural lands, which is the predominate source of windblown dust in the region, occurs when the friction velocity exceeds the threshold friction velocity (TFV) of the surface. Soil moisture influences the TFV, but the TFV of variably wet soils is virtually unknown in the region. The relationship between TFV and water content was ascertained for a sandy loam and four silt loams collected from field sites in eastern Washington. After moistening the soils to predetermined water contents, TFV was assessed from wind velocity and PM10 (particles with an aerodynamic diameter less than or equal to 10 µm) and TSP (total suspended particulate matter) concentration profiles above the soil surface inside a wind tunnel. Soil water content appeared to have little influence on TFV until gravimetric water content rose to 6.5 to 14.5% (depending on the soil). Trends in the relationship between TFV and soil matric potential suggested moistening soils had little influence on TFV until the matric potential exceeded -2.4 to -4.5 MPa. Thereafter, the TFV rose sharply with an increase in matric potential. The results of this study suggest that TFV is significantly influenced by soil moisture only when adsorption-dominated forces succumb to capillary-dominated forces during the moistening process. The transition appears to occur at a soil matric potential of about -5 MPa.

Last Modified: 12/17/2014
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