Estimating gas emissions from a farm with an inverse-dispersion technique

We use an inverse–dispersion technique to diagnose gas emissions (ammonia) from a swine farm. A backward Lagrangian stochastic (bLS) model gives the emission-concentration relationship, so that downwind gas concentration establishes emissions. The bLS model takes as input the average wind velocity and direction, surface roughness, and atmospheric stability. Despite ignoring windcomplexity andassuming a simplifiedsource configuration in the mod el calculations, we argue that with concentration andwindmeasuredsufficiently far from the farm the errors can be relatively small. An important part of our analysis was identifying periods likely to give erroneous results. The resulting emission calculations (6.5 and16 g animal � 1 day � 1 in March andJuly, respectively) are plausible in the light of