In modern animal
production houses, mechanical ventilation systems are used to create optimal
growing conditions for animals. Aerial pollutants from those houses, which have
become a growing political and environmental concern, are usually released
through ventilation fans at ground level and horizontal positions or positions
slightly tipping downwards.
And 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
reported 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.
Article by Manqing
Ying, et al, from North Carolina State University, Raleigh, USA.
Full access: http://mrw.so/3vbAmy
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