A Novel Downwind Odor Sampling Strategy for Transient Events; Combined Metalized-FEP Gas Sampling Bag, Sorbent Tube Transfer and Thermal Reconstitution

Downwind odor impact characteristics can be very different depending upon the size of the upwind point-source, interim topography and wind patterns. At one extreme, the downwind odor plume from a relatively large confined animal feeding operations (CAFO), located on a flat open plain and under stable, near-straight-line wind conditions can be rather broad, sustained and predictable relative to a fixed downwind receptor site. Conversely, the plume from a small point-source (e.g. such as a vent stack) located on irregular topography and under rapidly shifting wind patterns can be intermittent and fleeting. These transient odor events can be surprisingly intense and offensive, in spite of their fleeting occurance and perception. This work reports on efforts to develop a downwind odor sampling strategy which is optimized for sampling of such transient odor 'spikes'. This approach is based on combined air sampling with improved-material bags and preconcentration onto sorbent tubes. Initial results have been very promising. For example, approximate 10 fold increases in target odorant yields were realized for 900 mL sorbent tube transfers from 1-2 second 'burst' odor event bag-captures; when compared to equivalent direct collections at the same downwind receptor location but during perceived (stable) odor 'lull' periods. Results-to-date targeting refinement and validation of this integrated strategy for transient odor events are presented. Application to general odor sampling and point-source differentiation utilizing tracer gases is also presented.