Determination of temperature-dependent Henry's law constants of odorous contaminants and their application to human perception.
A new method was developed to measure Henry's law constants at varying temperatures and from these data determine enthalpies of reactions for volatilization of aqueous compounds. The method was applied to 2-methylisoborneol (2-MIB), geosmin, and trans-2,cis-6-nonadienal, which are three of the major odorous compounds found in natural and drinking water. The method used static headspace equilibrium in standard odor analysis flasks and SPME-GC/MS. Dimensionless Henry's law constants were determined at 20, 25, 32, and 39 degrees C in distilled water. Their values ranged from 0.002 to 0.02 and increased with increasing temperature. The study was continued by determining the effects of different concentrations of fulvic acid added to the aqueous media. Decreases of 5-40% in Henry's law constants were observed when fulvic acid was present; however the decrease was not correlated with the fulvic acid concentration. Fulvic acid at any concentration caused a small decrease in constants for geosmin and 2-MIB, yet a more substantial decrease was obtained for nonadienal. Finally, the gas-phase concentrations were predicted using measured Henry's law constants for known aqueous concentrations of 2-MIB, geosmin, and nonadienal at 25 and 45 degrees C. An increase in the gas-phase concentration was not correlated to an increase in human perception as determined by a trained human panel. It is concluded that, after some point, panelists were not able to perceive an increase in the odorant concentration. This has important implications for controlling nuisance odors in the environment.
Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, 413 Durham Hall, Blacksburg, Virginia 24061-0246, USA.
Pinar
P
Omür-Ozbek
Andrea M
AM
Dietrich
D000397:Air Pollution / Q000032:analysis*; D000447:Aldehydes / Q000032:analysis / Q000737:chemistry; D001578:Benzopyrans / Q000032:analysis / Q000737:chemistry; D001892:Camphanes / Q000032:analysis / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D009284:Naphthols / Q000032:analysis / Q000737:chemistry; D009812:Odorants; D009832:Olfactory Nerve; D010465:Perception / Q000502:physiology*; D013696:Temperature; D014835:Volatilization
D000447:Aldehydes; D001578:Benzopyrans; D001892:Camphanes; D009284:Naphthols; C005536:2-methylisoborneol; C412886:2,4-nonadienal; C001278:geosmin; C005023:fulvic acid