Application of a directional dust gauge to measurement of impaction at atmospheric salt

The potential for practical application of directional dust gauges to estimate inertial impaction of natural salt aerosols on obstacles the size of leaves was investigated at several centres in the south-west of Western Australia.The amounts and size distributions of aerosol particles varied with weather conditions but were similar to those measured at near-coastal locations elsewhere in the world. Results of measurements of salt impaction collected in dust gauges were resolved into a measure of the strength and direction for the directional components and an average value for all directions. The direction and strength components clearly showed that the greatest impaction was from strong (> 7.5 ms⁻¹) north-westerly to south-westerly winds from the ocean.Dust gauges were found to be useful standard collectors giving reproducible results in monitoring salt impaction. However relating the amount of impaction on different obstacles is complex. Therefore we suggest that if estimates of inertial impaction are required the best compromise would be to match the size of the dust gauge to be used for monitoring to the size (characteristics dimension) of the obstacle.