Odorants in the air include both volatile organic and volatile sulfur compounds. Movement of these compounds from swine feeding operations to surrounding community is thought to occur either through gas phase transport or through sorption onto particulate material (PM). This study was designed to measure both gaseous and PM sorbed odorants emitted from a swine facility and compare those compounds to background levels associated with rural environments. Volatile organic compounds (VOCs) were monitored using sorbent tubes and volatile sulfur compounds (VSC) were measured with both canisters and fluorescence detection. Samples were taken at an active swine facility (impacted) and at either a site 10 miles from any animal feeding operation (non-impacted) or upwind from the facility (control). PM filters were characterized by elemental analysis and odorant concentrations.
Key VOCs associated with odor included: volatile fatty acids (VFA), phenolic and indole compounds. Odorants in the swine housing areas had elevated levels of VFAs and phenol compounds, while pit fan areas had elevated levels of VFAs, phenol and indole compounds. In terms of concentration in air, total VFAs averaged 325 g m-3, total phenols 62.4 g m-3 and total indoles 1.6 g m-3. However, if concentrations are adjusted to odor activity value (= conc. of odorant in air/odor threshold concentration) total VFAs, phenols, and indole compounds averaged 6.8, 6.5, and 5.0, respectively. Concentrations of odorants measured in the spring and fall were higher than summer which all were substantially higher than winter. Daily concentrations of odorants had a diurnal pattern with early morning and late evening being peaks. Odor profiles changed with distance with VFAs, phenols, and indole compounds all above their odor threshold at the facility, but indole and phenol compounds being detected up to 1 mile north offsite. Concentrations of the most odorous compounds were all below their odorous thresholds values for samples taken at the control/non-impacted site. Compounds typically above odor threshold concentrations included butanonic acid, 3-methylbutanoic acid, 4-methylphenol, 4-ethylphenol, indole, and 3-methylindole.
Volatile sulfur compounds, hydrogen sulfide (H2S), methanethiol, and dimethyl sulfide were generally detected above their odor threshold values at the pit fan; however, during pumping of the deep pits levels of H2S rose rapidly to over 1000 ppbv from the building and over 800 ppbv 46 m downwind (approximately 50 times odor threshold) from the facility, but rapidly declined when pumping ceased. There was little to no rise in levels of the other VSC during pumping.
Levels of PM10 between buildings and 46 m downwind averaged 60.5 and 49.7 g m-3, respectively, but levels were not significantly different. Control and non-impacted sites averaged 18.3 g m-3, which were significant lower (p<0.05) than PM10 measured near buildings. There was little difference between levels of PM10 collected in the spring, summer or fall, but winter PM10 was significantly lower (p < 0.05) than the other seasons. Levels of VFA were enriched compared to both phenol and indole compounds when comparing PM sorbed to vapor phase concentrations. Elemental analysis of PM showed significant higher levels (p < 0.05) of nitrogen compared to samples taken from non-impacted areas; however, carbon and sulfur levels were not significantly different.
