Limited Scope Report Fugitive Dust Emissions: Development of a Real-time Monitor

Objectives. Current efforts to study fugitive dust (FD) are hampered by the lack of an effective, real-time instrument to measure the broad range of particle sizes that make up FD. To meet this need the overall objective of this project was to develop and evaluate a novel instrument capable of measuring, in real-time, ambient concentrations of particles between approximately 2 and 100 μm. This new instrument consisted of a new large particle inlet (LPI) combined with a commercially available particle spectrometer (Droplet Measurement Technology FM-100). The specific objectives of this work were to characterize this new instrument (LPIFM-100) in a series of laboratory, wind-tunnel and field experiments and compare its performance to traditional, commercially available samplers. The LPI-FM-100 should be able to classify particles into 20 size bins with mean bin sizes between 4 and 73 μm. The instrument should measure a broader range of particle sizes than with those obtained using other techniques to measure large particles. Technical Approach. This performance of this new instrument (LPI-FM-100) was characterized in the laboratory, in a wind-tunnel and in a series of intensive field experiments at Fort Drum, a U.S. Army military reservation in Jefferson County, New York. Laboratory measurements consisted of aspirating glass beads of known size directly into the FM-100. Wind-tunnel experiments of the new inlet (LPI) mounted on the FM-100 were conducted by measuring upstream and downstream particle concentrations to measure its sampling efficiency. In the field the LPI-FM-100 was deployed alongside traditional filter based particle measurements and other real-time instruments capable of measuring particles up to 20 μm in size. These measurements were compared and the performance of the new sampler evaluated. Results. Laboratory experiments with glass beads showed that the FM-100 was able to measure particles into 20 size bins and that the measured sizes were consistent with those measured by another light scattering instrument. Wind tunnel measurements found that, as predicted using computational fluid dynamics, the LPI was able to sample large particles at speeds as high as 5 m/s, with sampling efficiency decreasing with particle size and wind speed. During the field measurements it was found that there were periods of low particle concentrations corresponding to traffic-free conditions interspersed with high concentrations periods that were linked to local traffic. After these periods the concentrations quickly returned to background levels after the traffic passed. In the region where size measurements overlap the LPI-FM-100 size distributions were largely consistent with those measured using another real-time instrument. The LPI-FM100 detected the presence of particles larger than 30 μm during times of traffic movement. A comparison of the filter-based and LPI-FM-100 PM>10 values found there is a reasonable match between the measurements made by the two techniques. A first estimation of the fugitive number and mass distribution was obtained from the difference of the background and high concentration periods. This fugitive dust size distribution is mono-modal with a peak at approximatley 8 μm. The fugitive dust size distributions suggest a significant mass concentration of these particles in sizes larger than 10 μm. Benefits. Overall the findings indicate that military vehicle traffic generates a significant amount of fugitive dust that is highly dynamic and that there are significant peak concentrations near the roadway that quicly returns to background levels. The LPI-FM-100 was able to make fugitive dust concentration measurements in real-time even though much of this dust is larger than can be measured using traditional samplers