Dry Deposition of Particulate Matter Emitted from Cotton Gins - Particle Size Distribution of the Particulate Matter in the Downwind Plume

An engineering approach to analyze PM dry deposition due to gravitational settling is summarized in this paper. Particle horizontal settling distance is determined based upon wind speed and particle terminal settling velocity. New PSD in the downwind plume is calculated based upon particle horizontal settling distance and source PSD. Results of this research indicate that change of PSD in the downwind plume is a function of wind speed, downwind distance and source PSD. Both MMD and GSD in the downwind plume decrease with increase of downwind distance and source MMD. When the MMD of the source is high, there was a big change in the MMD and GSD of the dust in the downwind plume. Likewise, there was a big change in the MMD and GSD of dust in the downwind plume as downwind distance is increased. However, the change of wind speed has an inverse impact on the change of downwind PSD. MMD and GSD in the downwind plume decrease with decrease of wind speed. Gravitational settling causes significant change of MMD and GSD in the downwind plume and thus, has significant impact on the PM10 sampling error problems. Future research is needed to quantify this impact for more accurate PM10 measurement