Laing D G, Eddy A, Best D J
Faculty of Science and Technology, University of Western Sydney, Richmond NSW, Australia.
Physiol Behav. 1994 Jul;56(1):81-93. doi: 10.1016/0031-9384(94)90264-x.
Among the most obnoxious stimuli that the population at large is exposed to during everyday life are odorous emissions from sewage treatment plants. Such emissions are complex and contain many different types of odorants that vary in quantity depending upon the contents and efficiency of treatment processes. Because little is known about how individual odorants in complex mixtures affect the perception of each other, it is difficult to develop mathematical models that can predict the pleasantness, strength, and quality characteristics of an emission at different distances from a source. In the present study, the interactions of the four major types of odorants emitted by treatment plants worldwide, namely, hydrogen sulphide, isovaleric acid, butanethiol, and skatole, were investigated by measuring the perceived intensity of individual odorants alone and in mixtures, and the overall perceived intensity, unpleasantness, and qualities of mixtures. In addition, models for predicting odor strength were investigated. The results indicated that (i) the perceived odor intensity (odor strength) of mixtures of the odorants was equal or greater than that of any of the individual constituents, but less than the sum of their intensities. However, as the number of components in a mixture increased, the intensity of the most dominant component provided a good approximation of the intensity of the mixture. (ii) The vector model of intensity summation also satisfactorily predicted the odor intensity of mixtures containing two, three, or four of the odorants investigated. (iii) In no instance was the intensity of one odorant enhanced by another, i.e., no synergistic interactions occurred; the greater the number of odorants in a mixture, the greater was the degree of suppression of the individual constituents. (iv) The greater the number of constituents in a mixture the more difficult it became to identify individual constituents. (v) Hydrogen sulphide was the least frequently suppressed constituent, and isovaleric acid and skatole were the most frequently suppressed constituents in mixtures. (vi) The unpleasantness of mixtures was usually greater than that of the individual constituents, indicating that models used for predicting complaint levels in communities affected by sewage odor and based on assumptions related to a single odorant, e.g., hydrogen sulphide, will underestimate the number of complaints. Even mixtures with low but above threshold concentrations of these odorants are likely to generate complaints.
在日常生活中，普通大众接触到的最令人厌恶的刺激之一是污水处理厂散发的气味。这些排放物成分复杂，包含许多不同类型的气味物质，其数量会根据处理过程的内容和效率而有所不同。由于对于复杂混合物中的单个气味物质如何相互影响人们的嗅觉知之甚少，因此很难建立数学模型来预测在离源不同距离处排放物的愉悦度、强度和质量特征。在本研究中，通过测量单独的和混合状态下的单个气味物质的感知强度，以及混合物的总体感知强度、不愉快程度和性质，对全球污水处理厂排放的四种主要气味物质，即硫化氢、异戊酸、丁硫醇和粪臭素之间的相互作用进行了研究。此外，还对预测气味强度的模型进行了研究。结果表明：（i）气味物质混合物的感知气味强度（气味强度）等于或大于任何单个成分的强度，但小于它们强度之和。然而，随着混合物中成分数量的增加，最主要成分的强度能很好地近似混合物的强度。（ii）强度求和的向量模型也能令人满意地预测包含所研究的两种、三种或四种气味物质的混合物的气味强度。（iii）在任何情况下，一种气味物质的强度都不会因另一种气味物质而增强，即没有发生协同相互作用；混合物中气味物质的数量越多，单个成分的抑制程度就越大。（iv）混合物中的成分数量越多，识别单个成分就越困难。（v）硫化氢是混合物中最不容易被抑制的成分，而异戊酸和粪臭素是混合物中最常被抑制的成分。（vi）混合物的不愉快程度通常大于单个成分，这表明用于预测受污水气味影响的社区投诉水平且基于与单一气味物质（如硫化氢）相关假设的模型，将会低估投诉数量。即使是这些气味物质浓度低但高于阈值的混合物也可能引发投诉。
