Comparison of PI‐SWERL with dust emission measurements from a straight‐line field wind tunnel

Abstract

[1] The Portable In situ Wind ERosion Lab (PI-SWERL) was developed to measure dust emissions from soil surfaces. This small, portable unit can test the emissivity of soils in areas that are difficult to access with a field wind tunnel, and can complete a larger number of tests in less time. The PI-SWERL consists of a cylindrical enclosure containing an annular flat blade that rotates at different speeds, which generates shear stress upon the surface. The shear stress generated by PI-SWERL results in the entrainment of particles including dust. PI-SWERL was developed to provide an index of dust emission potential comparable to the field wind tunnel. The PI-SWERL dust emission results were compared against those obtained from a $12 m long, 1 m wide, 0.75 m high straight line suction-type portable field wind tunnel by conducting collocated tests at 32 distinct field settings and soil conditions in the Mojave Desert of southern California. Clay-to sand-rich soils that displayed a range of crusting, gravel cover, and disturbance were tested. The correspondence between dust emissions (mg m À2 s À1 ) for the two instruments is nearly 1:1 on most surfaces. Deviation between the two instruments was noted for densely packed gravel surfaces. For rough surfaces a correction can be applied to the PI-SWERL that results in comparable dust emission data to the wind tunnel. PI-SWERL can be used to complement research efforts in aeolian geomorphology aimed to quantify spatial and temporal patterns of dust emissions as well as air quality research related to dust emissions.

Fugitive Dust Emissions from Off-Road Vehicle Maneuvers on Military Training Lands

“…The PI-SWERL instrument has been evaluated as a method for measuring dust emissions potential from wind erosion events and results have been published in several refereed journal publications (Kavouras et al, 2009;Etyemezian et al, 2007;Sweeney et al, 2008). These studies have demonstrated that this instrument provides data comparable with a portable straightline wind tunnel on a wide range of surface conditions.…”

“…The most prevalent error comes about with use on very rough surfaces such as a gravel-packed bed. Because the instrument uses the principle of Coulette flow, which is the shearing force developed between two infinitely flat plates, the calculated friction likely underestimates the actual friction developed on a rough surface (Sweeney et al, 2008). Another limitation of this system is that it does not generate a velocity profile and boundary layer condition as observed in nature.…”

“…When attempting to measure fugitive emissions in the field, ensuring isokinetic sampling conditions is difficult given the unpredictability of the weather (Vrins, 1996) One method to overcome this problem is to utilize a wind tunnel to initiate high wind speeds over a given land area. Several studies have utilized in-situ semi-portable wind tunnels that are set up directly in the field on the surface of interest (Sweeney et al, 2008;Marticorena and Bergametti, 1997). Other studies have utilized large laboratory wind tunnels to control both wind and soil surface conditions to some degree (Hagen, 1999;Guoliang et al, 2003;Kohake et al., 2010).…”

“…Published literature suggests that the RPM value can be directly correlated to a shear stress on the soil surface using Equation 4.1 (Sweeney et al, 2008). The value for K R , a roughness correction factor, is largely based on observation of the site and can cause wide variations in the resulting friction velocity.…”

Atmospheric inversion of SO<sub>2</sub> and primary aerosol emissions for the year 2010

“…Actual measurements characterizing dust and sea-salt emission processes, either in controlled environments (such as in a wind tunnel) or in the real world, remain limited (e.g., O'Dowd et al, 1997;Alfaro et al, 2004;Rajot et al, 2003;Roney and White, 2006;Sweeney et al, 2008;Sow et al, 2009). Parameterizations of emissions either are empirical, as it is often the case for seasalt aerosols (de Leeuw et al, 2011), or combine a physical basis with a more empirical diagnostic of source areas, as is sometimes done for dust (Marticorena et al, 2004).…”