ROAD DUST AS AN INDICATOR FOR AIR-POLLUTION TRANSPORT AND DEPOSITION - AN APPLICATION OF SPOT IMAGERY

A simulation model for atmospheric diffusion and dry deposition of coarse dust particles developed at the Paul Scherrer Institute was recently applied to calculate the dispersion and deposition of road-generated dust from the Dalton Highway, which is a high-speed gravel road in arctic Alaska traveled mainly by large vehicles. The propelled dust is deposited on the adjacent vegetation where it may cause detrimental effects to the plants of the highly fragile tundra. During a field experiment in 1991, all meteorological parameters as well as the size distribution of the deposited dust particles were measured. This data was used to calculate the dust distribution pattern and the amount of dust transferred into the vegetation at specific locations along the Dalton highway. The scope of this article is to identify and, as far as possible, to quantify this dust deposition pattern along the Dalton Highway by multispectral SPOT imagery. The Spatial distribution of the dust on both sides of the road is distinctly visible in the XS3 channel (0.79-0.89 mu m) of a SPOT satellite image. On the basis of the ground reflectance and the reflectances of pure dust and pure vegetation, the dust load can be calculated. The dust load depends on the particle size distribution, which can be derived from the size spectra measured in the field experiment. The spatial dust load obtained from the SPOT data is compared with the distribution computed with the simulation model. As the simulation is based on only a limited number of days, the dust load scaling is arbitrary. Taking this fact into account, the general shapes of the two distributions agree remarkably well within a strip of about 1 km width along the road. Apart from this application on a local scale, suspended dust might also be detected on larger scales, for example, as volcanic ash or as tropospheric or stratospheric aerosols.