Instrumentation to Quantify Soil and PM10 Flux Using a Portable Wind Tunnel

Abstract

Wind erosion threatens soil productivity and air quality in the Columbia Plateau region of the Pacific Northwest United States. Management practices are sought that will abate erosion, but limitations exist in measuring the effectiveness of these practices in reducing erosion. Portable wind tunnels are ideal tools that can be used to assess the impact of management practices on erosion. A portable wind tunnel, characterized by a 7.3-m long working section that is 1-m wide and 1.2-m high and capable of generating winds of 20 m s-1, was instrumented to measure wind speed as well as soil loss and PM10 (particulate matter =10µm in diameter) emissions in the laboratory and field. Wind speed was measured at various heights above the soil surface using pitot tubes. Creep was measured using trays while saltation and suspension were measured using an isokinetic slot sampler. PM10 concentration was measured by mounting Dustrak inlets at various heights above the soil surface both at the windward and leeward position in the wind tunnel. PM10 loss was determined by integrating horizontal PM10 flux from the soil surface to plume height and subtracting the mass flux at the windward position from that at the leeward position in the tunnel. Pitot tubes and Dustrak inlets were mounted on a sliding instrument rack. Auxiliary devices (e.g. datalogger) were mounted on the frame of the wind tunnel to enhance portability and timeliness of operations. The instrumentation package has performed well in assessing soil and PM10 flux in the laboratory and field.