Air samples were collected or analyzed onsite from finishing, nursery and breeding and gestation operations twice weekly for a 10-wk period during each of two summers. Samples were analyzed for odor, hydrogen sulfide and additional specific gases (total of 21 gases routinely quantified) at both the building or manure storage area and approximately 50, 100, and 200 m downwind. Climatic conditions were recorded during each visit. From the collected data an odor prediction equation was developed based on the measured gases. Approximately 50% of the variation observed in odor could be accounted for by the developed equation. In addition, specific gases were individually correlated to odor to determine if any, individually, could serve as a surrogate for odor. While hydrogen sulfide and ammonia were the two best indicators, each only accounted for approximately 25% of the odor response.
Equations were formulated to estimate downwind concentrations of the gases and odor, based on the concentration observed at the source. All equations were compound specific. Results indicate that climatic variables, while included, were not as important to predictive capability as was source concentration or distance downwind. Prediction equations for odor, hydrogen sulfide and the volatile fatty acids, a specific group of the analyzed gases, were reasonably capable of estimating downwind concentrations, accounting for as much as 64% of the response variation. For these compounds and odor, if a producer knew the source concentration the producer could estimate the property line concentration with a reasonable degree of certainty provided that distance to the property line, temperature and humidity were known.
