Physical modeling and numerical simulation of factors leading to high PM10 emission fluxes from ground source fugitive dust with emphasis on Owens (dry) Lake soils.

摘要

The Saltation Wind Tunnel (SWT) at the University of California at Davis was used to simulate natural sources of fugitive atmospheric dust such as those resulting from lake playas, fallow fields, and other arid land environments. Specifically, four Owens (dry) Lake soils (an EPA superfund site for particulate matter) were studied and were chosen based on known dust activity on the lake playa in order to establish an emission inventory for this site. The Saltation Wind Tunnel facility is an environmental boundary layer tunnel developed in the spirit of R. A. Bagnold, 1941 who used a similar wind tunnel to study the movement of desert sands. The use of improved instrumentation including light scattering photometer aerosol detectors and pressure transducers along with new analysis techniques allows the measurements to be extended to include dust emissions of PM₁₀ and PM_2.5 (particulate matter of 10 microns and 2.5 microns aerodynamic diameter).; These instruments are used to data-acquire velocity and dust concentration profiles simultaneously within the wind tunnel as a function of fetch along the bed of soil, surface measurements which have not been previously accomplished in any setting (field or laboratory). A control volume analysis is used to obtain emission rates. The relative dependence of the emission rate on variables such as wind shear and surface variability is addressed with this technique. These variables are imperative to understanding and modeling the mechanisms of atmospheric dust entrainment and establishing fugitive dust emission inventories.; A numerical scheme for the diffusion equation of Pasquill, 1962, using the insight gained from the wind tunnel, is used to computationally represent the diffusion physics of the process. The numerical scheme calculates concentration profiles along the streamwise direction, which are then directly compared to the profiles obtained in the wind tunnel. Initial comparisons indicate good agreement implying that the physical mechanism of advection-diffusion is realistically captured in the numerical model.