Validation of a new method for directional dust monitoring

Fugitive dust from industrial sites is problematic to quantify and can be associated with nuisance complaints. Despite significant limitations, the British Standard 1747 Part 5 (BS 1747:5) directional dust gauge remains preferred for monitoring fugitive dust flux on site boundaries. An alternative directional dust gauge, DustScan, was developed at the University of Leeds, UK, and uses cylindrical adhesive ‘sticky pads’ to sample dust in flux. With this sampler, dust capture is measured as soiling, as opposed to mass, with the BS 1747:5 sampler. An Aerosol Test Tunnel (ATT) was developed to evaluate the performance of the DustScan sampler. Atmospheric turbulence was simulated using a coarse grid generator and maintained as rough-wall channel flow by roughness elements fixed to its floor and roof of the ATT. A polydisperse test dust was introduced upwind to form a cloud at the sampler. DustScan directional dust gauges were repeatedly exposed to aliquots of test dust at wind speeds of 2–10 m s−1 in the ATT. Dust soiling levels either side of the gaugeʹs centreline (relative to the incident direction) were compared to demonstrate that the DustScan sampler is directionally accurate. Much lower proportions of antithetic sampling (dust catch on the downwind face of the gauge) occurred than for the BS 1747:5 sampler. The sampled particle size selection was related to the ratio of particle stop distance (s) to sampler diameter (D) ratio, s/D, showing that the particle size cut point fell with increasing wind speeds. A preliminary assessment of collection efficiency (CE) was made by determining dust mass after controlled ignition of selected sticky pad samples. Although dust saturation of the sticky pads can lead to sample loss over prolonged exposure periods, this loss is relatively small over the 1–2 week intervals established as appropriate for the DustScan sampler. This need for shorter sampling intervals is considered to outweigh the convenience of the longer exposure time but significantly poorer dust sampling characteristics of the BS 1747:5 sampler.