Field-Testing a Portable Wind Tunnel for Fine Dust Emissions

A portable wind tunnel has been developed to allow erodibility and dust emissions testing of soil surfaces with the premise that dust concentration and properties are highly correlated with surface soil properties, as modified by crop management system. In this study we report on the field-testing of the portable wind tunnel. The test section of the tunnel is one meter high, ½ meter wide, and 6 meters long. The wind profile was conditioned to simulate the wind above a level, smooth, fine sandy loam surface. Dust samples were gathered through an isokinetic vertical slot sampler, with a GRIMM particle size analyzer used to test PM10 and PM2.5 emissions. Isokinetic conditions were achieved by attaching a vacuum to the vertical slot sampler. Larger saltating particles settled into a tray at the bottom of the slot sampler while smaller suspended particles were pulled through a vacuum tube attached to the sampler. The GRIMM analyzer sampled from the airborne portion of the dust, while the remaining dust was caught on two 20 cm by 25 cm rectangular hydrophilic glass fiber filters. After initially running the wind tunnel on a specific soil, a fine, dust-free quartz sand was added through a feeder in the front of the tunnel to abrade the surface and generate dust emissions. This presentation will describe the process used to condition the wind profile and compare the particle size data measured by the GRIMM analyzer with the size of particles captured on the filters, as measured by a Coulter Counter.