John A. Gillies

Recent progress in Aeolian research

Aeolian processes-involving erosion, transportation, and deposition of sediment by wind-occur in a variety of environments including coastal areas, semiarid and arid regions, and agricultural fields. Aeolian processes also occur on some planetary bodies, notably Mars and possibly Venus and on Saturns moon Titan. Aeolian processes are responsible for the emission and/or mobilization of dust and the formation of areas of sand dunes. Fluctuations in the intensity and geographical extent of wind transport of sediments during the Quaternary have produced an important paleoclimatic record in loess deposits and areas of vegetationstabilized sand dunes.

Changes in the saltation flux following a step-change in macro-roughness: Effect of Roughness on Saltation

Author(s): Gillies, John A; Etyemezian, Vicken; Nikolich, George; Nickling, William G; Kok, Jasper F

Entrainment of radio frequency chaff by wind as a function of surface aerodynamic roughness.

Abstract Radio frequency (RF) chaff (~2-cm × 25-µm diameter aluminum-coated glass silicate cylinders) released by military aircraft during testing and training activities has the potential to become entrained by wind upon settling to the Earth’s surface. Once entrained from the surface there is the potential for RF chaff to be abraded and produce PM10 and PM2.5 , which are regulated pollutants and pose health concerns. A series of portable wind tunnel tests were carried out to examine the propensity of RF chaff to become entrained by wind by defining the relationship between the threshold friction velocity of RF chaff (u *t RF chaff) and aerodynamic roughness (z o ) of surfaces onto which it may deposit. The test surfaces were of varying roughness including types near the Naval Air Station (NAS), Fallon, NV, where RF chaff is released. The u *t of this fibrous material ranged from 0.14 m/sec for a smooth playa to 0.82 m/sec for a rough crusted playa surface with larger cobble-sized (~6–26-cm diameter) rocks rising above the surface. The u *t RF chaff is dependent on the z o of the surface onto which it falls as well as the physical characteristics of the roughness. The wind regime of Fallon would allow for chaff suspension events to occur should it settle on typical surfaces in the area. However, the wind climatology of this area makes the probability of such events relatively low.

Comparison and evaluation of chemically speciated mobile source PM2.5 profiles

Mobile sources are significant contributors to ambient fine particulate matter (PM2.5). An important method for resolving the mobile source contribution is chemical mass balance (CMB) receptor modelling, which requires chemically speciated source profiles to estimate source contributions. This paper examines similarities and differences in US mobile source PM2.5profiles containing data for elements, ions, elemental (EC) and organic carbon (OC) and, in some cases, speciated organics. Characteristics of the data include variability in the relative contributions of elements and ions among supposedly similar sources and the wide range of elemental to organic carbon ratios (0.60 ± 0.53 to 1.42 ± 2.99) for light-duty gasoline vehicles (LDGVs), indicating LDGVs may be significant sources of EC emissions. Different populations of the same class of emitters also exhibited considerable variability in the relative emissions of other species, suggesting caution be exercised when selecting and using receptor models to...