Open-path transmissometry to determine atmospheric extinction efficiency associated with feedyard dust

Open-lot, concentrated animal feeding operations (CAFOs) in the southern High Plains, such as cattle feedyards and open-lot dairies, emit fugitive particulate matter (PM) that occasionally reduces downwind visibility. The long-path visibility transmissometer (LPV) can be used to measure changes in total atmospheric extinction, a direct measure of path-averaged visibility impairment. To our knowledge, no researchers have used transmissometry as a surrogate to estimate aerosol concentrations downwind of open-lot livestock facilities. We compare time-resolved PM mass concentrations (g m -3) and atmospheric extinction coefficients (km -1) measured simultaneously along the downwind boundary of a commercial cattle feedyard to compute "extinction efficiency," the change in atmospheric extinction that results from a unit change in PM mass concentration. Expected values for the in-situ extinction efficiency of total suspended particulate (TSP) and its fraction less than 10 microns (PM 10) aerodynamic equivalent diameter (AED) are 0.2 to 0.5 m 2 g -1 and 0.4 to 0.8 m 2 g -1, respectively. Determination of the atmospheric extinction efficiency of feedyard dust will enable transmissometry to be used as an intuitive, real-time surrogate for measuring time-averaged PM 10 and/or TSP concentrations. 2008 American Society of Agricultural and Biological Engineers.

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