Solid-Phase Microextraction as a Novel Air Sampling Technology for Improved, GC-Olfactometry-Based, Assessment of Livestock Odors

Air sampling and characterization of odorous livestock gases is one of the most challenging analytical tasks. This is due to low concentrations, physicochemical properties, and problems with sample recoveries for typical odorants. Livestock operations emit a very complex mixture of volatile organic compounds and other gases. Many of these gases are odorous. Relatively little is known about the link between specific VOCs/gases and specifically, about the impact of specific odorants downwind from sources. In this research, solid-phase microextraction (SPME) was used for field air sampling of odors downwind from swine and beef cattle operations. Sampling time ranged from 20 min to 1 hr. Samples were analyzed using a commercial GC-MSOlfactometry system. Odor profiling efforts were directed at odorant prioritization with respect to distance from the source. Results indicated the odor downwind was increasingly defined by a smaller number of high priority odorants. These ‘character-defining’ odorants appeared to be dominated by compounds of relatively low volatility, high molecular weight, and high polarity. In particular, pcresol alone appeared to carry much of the overall odor impact for swine and beef cattle operations. Of particular interest was the character-defining odor impact of p-cresol as far as 16 km downwind of the nearest beef cattle feedlot. The findings are very relevant to scientists and engineers working on improved air sampling and analysis protocols and on improved technologies for odor abatement. More research evaluating the use of p-cresol and a few other key odorants as a surrogate for overall odor dispersion modeling is warranted