Odor-cued grab air sampling for improved investigative odorant prioritization assessment of transient downwind environmental odor events

Authors: WRIGHT, DONALD - Don Wright & Associates; Koziel, Jacek; KUHRT, FRED - Volatile Analysis Corporation; IWASINSKA, ANNA - Volatile Analysis Corporation; EATON, DAVID - The Epsilon Company; WAHE, LANDON - Iowa State University

Submitted to: ACS Omega
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2024
Publication Date: 6/27/2024
Citation: Wright, D.W., Koziel, J.A., Kuhrt, F., Iwasinska, A., Eaton, D.K., Wahe, L. 2024. Odor-cued grab air sampling for improved investigative odorant prioritization assessment of transient downwind environmental odor events. ACS Omega. 9(27):29290-29299. https://doi.org/10.1021/acsomega.4c00531.
DOI: https://doi.org/10.1021/acsomega.4c00531

Interpretive Summary: Industrial zoning may locate potential odor sources close to each other and upwind of residential areas. Identifying an offending odor source from multiple potential upwind sources can be difficult due to the randomly on/off ‘spike’ nature of characteristic odors. Typically, these odor spikes last only a few seconds, interspersed with long periods where the odor is undetectable or only faintly detectable. In this research, a team from Don Wright & Associates, USDA ARS-Bushland (Texas), West Texas A&M University, Volatile Analysis Corporation, The Epsilon Company, and Iowa State University developed an air sampling protocol to capture these ‘spike’ events. The initial field-trial of the protocol showed that identifying an odor emission source from among multiple 'potential' upwind point-sources is feasible. This research can help with improved assessment for addressing local air quality issues.

Technical Abstract: A critical prelude to any community odor assessment should be the prioritization of specific chemical odorants which are most responsible for targeted downwind odors. Unfortunately, and historically, this is a step which has often been bypassed or overlooked. However, correct understanding of the specific impactful VOCs can inform to the follow-on sampling, analytical and remediation strategies which are most appropriate and efficient; based upon the chemistry behind the issue. With this understanding, the techniques and sampling strategies presented herein should be viewed as a qualitative prelude to rather than an addendum to follow-on routine, automated downwind odor monitoring. Downwind odor characteristics can vary, depending upon the size of the upwind source, interim topography, and wind conditions. At one extreme, the downwind odor plume from a relatively large source located on a flat open plain and under stable, near-straight-line wind conditions can be rather broad, sustained, and predictable. In contrast, the plume from a small point-source (e.g., a roof vent stack) located on irregular topography and under rapidly shifting wind conditions can be intermittent and fleeting (‘spikes’ or ‘bursts’). These transient odor events can be surprisingly intense and offensive despite their fleeting occurrence and perception. This work reports on improving and optimizing an environmental sampling strategy for odorant prioritization from such transient downwind odor conditions. This optimization addresses the challenges of (1) sampling of transient odor 'spikes' and (2) prioritizing odors/odorants from multiple, closely co-located point sources under transient event conditions. Prioritizing is defined as identifying the key impactful odorants downwind. Grab air sampling protocol refinement has emerged from actual community environmental odor assessment projects. The challenge of assessing transient odor events has been mitigated by utilizing: (a) rapid, odor-cued whole-air grab sampling (i.e., activated by and synchronous with the perceived sensory spikes) into metalized fluorinated ethylene polymer (m-FEP) gas sampling bags; (b) immediate transfer from bags onto solid-phase microextraction (SPME) fibers or sorbent tubes; (c) maintaining refrigerated storage and shipment conditions between field collection and in-laboratory analysis. Results demonstrated approximately 11-fold increases in target odorant yields for 900 mL air sample capture on sorbent tubes transfers from 2-3 s 'burst' odor event bag-captures compared to equivalent direct collections (with sorbent tubes) at the same downwind receptor location but during perceived (stable) odor 'lull' periods. An application targeting general odor sampling and point-source differentiation utilizing tracer gases is also presented.