Determination of efficiency of Vaseline slide and Wilson and Cooke sediment traps by wind tunnel experiments

The trap efficiency of a catcher in wind erosion measurements plays a significant role, and in many cases suspension trap efficiencies at high wind velocities are still unknown. The sediment trap efficiency generally changes with particles size and with wind speed. In this study, the efficiency of Vaseline Slide (VS) and Modified Wilson and Cooke (MWAC) catchers were determined with different sand particle sizes (< 50, < 75, 50-75, 200-400, and 400-500 mu m) at a fixed wind speed (13.3 ms(-1)) and with different soil textures at different wind velocities (10.3, 12.3, and 14.3 ms(-1)) in the wind tunnel of the International Center for Eremology (ICE), Ghent University, Belgium. The traps were placed at different heights (4, 6.5, 13, 20, 120, and 192 cm for VS and 1.5, 3, 5, 8, 11, and 30 cm for MWAC) to catch saltating and suspended sediments in a 12-m long, 1.2-m wide and 3.2-m high working section of the wind tunnel. In the sand particle experiments, the efficiency of the VS catcher was 92% for particles smaller than 50 mu m and decreased with increasing particles size, falling to 2.2% for 400-500 mu m particle size at 13.4 ms(-1). However, the MWAC's efficiency was 0% for particles smaller than 50 mu m and increased with increasing particle size to 69.5% at 400-500 mu m. In the experiments with different soil textures, the efficiency of each catcher significantly changed with soil and with wind speed. It also considerably varied with the catchers: for instance, for sand (S), the MWAC efficiency was very high (67.4, 113.4, and 90.5% at 10.3, 12.3, and 14.4 ms(-1), respectively) while the efficiency of VS was relatively very low (5.2, 4.4, and 1.9% at 10.3, 12.3, and 14.4 ms(-1), respectively). Results indicated that the efficiency depends critically on the particle size, type of catcher, and wind speed, and these could be helpful to increase the robustness of wind erosion measurements.