Saarenvirta, Gianna

This study reports on as series of laboratory wind tunnel experiments aimed at furtheringour understanding of aggregate breakdown and dust release during aeolian transport, and thereby, has implications for air quality and the management of dust emission through water application. Particles aggregates 500 um in diameter were formed and isolated by the wetting, drying, and screening of playa sediments collected from Owens Lake. They were then released into a boundary-layer flow within the Trent Environmental Wind Tunnel (TEWT), whereupon they either slid, rolled and/or saltated downwind. The concentration of PM10 and the particle size of the aggregates were monitored throughout each test along the central axis of the tunnel. The results confirm that aggregate breakdown did occur, resulting in the production and emission of dust. The relative efficiency of aggregate abrasion in the production of silt sized particles during aeolian transport was calculated using normalized indices, providing a starting point for the modelling of similar systems in a natural setting. The results indicate that for every metre of transport, the abrasion of a 500 um aggregate formed from playa sediment may release a volume of dust roughly equivalent to that of a single silt particle that is 60 um diameter. Conversely, aggregate formation is found to produce 1-4% of dust as compared to an equivalent volume of disaggregated silt when exposed to a given airflow above the threshold for saltation.

Author Keywords: Aeolian abrasion, Aggregate breakdown, Owens Lake, PM10, Saltation, Wind Tunnel