|Li, Hong - IOWA STATE UNIVERSITY|
|Burns, Robert - IOWA STATE UNIVERSITY|
|Xin, Hongwei - IOWA STATE UNIVERSITY|
Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2008
Publication Date: April 15, 2008
Citation: Trabue, S.L., Scoggin, K.D., Li, H., Burns, R., Xin, H. 2008. Field sampling method for quantifying odorants in humid environments. Journal of Environmental Science and Technology. 42:3754-3750. Interpretive Summary: A popular technique to capture volatile organic compounds (VOCs)that are associated with odor is thermal desorption using sorbent tubes. The technique uses adsorbents to capture and concentrate VOCs in air that are removed from the adsorbents after heating. A common adsorbent typically used in these studies is carbon molecular sieves (CMS), but there have been few studies to validate how well they trap and release VOCs in humid enviornments, conditions commonly encountered around livestock production facilities. The objectives of this study were to develop a robust sampling technique for measuring VOCs in humid environments. Sorbent material used for this study included Tenax (a porous polymer resin), graphitized carbon, and CMS. Sorbent tubes with CMS material performed poorly under humid conditions due to excessive sorption of water during sampling affecting subsequent analysis. Issues related to excessive adsorbed water on CMS sorbent tubes during sampling were effectively addressed by either heating them during sampling or by purging them with dry nitrogen gas after sampling. Heating of tubes resulted in little loss of VOCs, while dry-purging tubes resulted in a loss of compounds and loss of analytical reproducibility. Tenax sorbent tubes had loss of the more volatile VOCs and tended to form artifacts with increasing amounts of air sampled. Sorbent tubes made with graphitized carbon performed best with good recovery of VOCs in humid environments. Due to the superior performace of the graphitized carbon sorbent tubes they were selected for use in the field. Field samples taken from inside a swine feeding operation showed that butanoic acid, 4-methyl phenol, 4-ethylphenol, indole, and 3-methylindole were the compounds commly detected above their odor threshold values. Field samples taken from a poultry facility demonstrate that butanoic acid and 4-methyl-butanoic acid, and 4-methylphenol, were detected consistently above their odor threshold values. The information presented in this paper is intended to be used by researchers measuring air quality at animal production facilities.
Technical Abstract: Most air quality studies in agricultural environments typically use thermal desorption analysis for quantifying volatile organic compounds (VOC) associated with odor. Carbon molecular sieves (CMS) are popular sorbent materials used in these studies. However, there is little information on the effectiveness of CMS materials to quantify odorants when sampling in humid environments. The objectives of this study were to develop a robust sampling technique for measuring VOCs in humid environments. Test atmospheres were generated at ambient temperatures (23 + 1.5 degrees C) and 25, 50, and 80 percent RH. Sorbent material used included Tenax, graphitized carbon, and CMS. Sorbent tubes were challenged with 2, 4, 8, 12, and 24 L of air at various RHs. Sorbent tubes with CMS material performed poorly at both 50 and 80 percent RH due to excessive sorption of water, while Tenax sorbent tubes had breakthrough of the more volatile compounds and tend to form artifacts with increasing volumes of air sampled. Sorbent tubes containing graphitized carbon material performed best with quantitative recovery of all compounds at all RHs and sampling volumes tested. Water sorption was effectively reduced in CMS tubes by either heating of tubes during sampling (15 degrees C above ambient temperature) or dry-purging of tubes post sampling. Heating of tubes resulted in no significant loss compounds, while dry-purging resulted in a significant loss of compounds and high variability in measurement. Field samples taken from inside a swine feeding operation showed that butanoic acid, 4-methyl phenol, 4-ethyl phenol, indole, and 3-methyl indole were the compounds detected above their odor threshold values. Field samples taken from a poultry facility demonstrate that butanoic and 4-methyl butanoic acids along with 4-methyl phenol were the compounds detected consistently above their odor threshold values.