Modeling Plume-Rise of Air Emissions from Animal Housing Systems: Inverse AERMOD

Abstract

As fate and transport of air emissions from animal housing systems is of increasing concern, dispersion models have become commonly used tools to estimate the downwind concentrations of pollutants at certain locations surrounding the animal production farms. In application of Gaussian dispersion model for downwind concentration predictions of animal housing emissions, unknown plume rise (△h) and plume shape of the horizontally emitted plumes from animal housing systems have been vital weak points challenging the accuracy of the model predictions. This paper reports an inverse AERMOD modeling study to derive the plum rises of PM10 emissions from mechanically ventilated egg production houses based upon field measurements of PM10 emission rate, downwind concentrations, and meteorological conditions. In total, 87 hourly plume rises were found for 20 days (five days per season for four seasons, from fall 2008 to summer 2009). The mean plume rises for fall 2008, winter 2008, spring 2009 and summer 2009 were 16.2 m (SE = 11.2 m), 7.9 m (SE = 9.5 m), 16.5 m (SE = 12.4 m), and 14.3 m (SE = 10.0 m), respectively. The relationships between plume rises and various factors were tested. While the diurnal patterns of the plume rises were not consistent among different selective days, they generally followed the diurnal patterns of house ventilation rates. Plume rise for weekends were significantly higher than those for weekdays in fall. Multiple linear regression showed a significant positive relationship (p = 0.0134) between wind speed and the plume rises. Ambient relative humidity and total volume flow were also found to be slightly (p = 0.171 and 0.217, respectively) related to the plume rises.