An electronic nose for odour annoyance assessment

Although in most cases annoying atmospheric emissions do not menace public health, they are less and less tolerated because of the effects on quality of life. Several approaches have been proposed to face this problem but none of them offers a completely satisfying solution. The development of electronic noses, which promise to mimic human sense of smell by means of a sensor array and a pattern recognition model, offers new interesting perspectives. In this paper, an electronic nose based on conducting polymer sensors and a fuzzy logic-based pattern recognition system is tested with waste water samples, obtaining 87% recognition rate on the test set. Current limits of this new technology are discussed and a strategy for their overcoming is proposed.     

Measurement of odor intensity by an electronic nose

The possibility of using electronic noses (ENs) to measure odor intensity was investigated in this study. Two commercially available ENs, an Aromascan A32S with conducting polymer sensors and an Alpha M.O.S. Fox 3000 with metal oxide sensors, as well as an experimental EN made of Taguchi-type tin oxide sensors, were used in the experiments. Odor intensity measurement by sensory analysis and EN sensor response were obtained for samples of odorous compounds (n-butanol, CH3COCH3, and C2H5SH) and for binary mixtures of odorous compounds (n-butanol and CH3COCH3). Linear regression analysis and artificial neural networks (ANN) were used to establish a relationship between odor intensity and EN sensor responses. The results, suggest that large differences in sensor response to samples of equivalent odor intensity exist and that sensitivity to odorous compounds varies according to the type of sensors. A linear relationship between odor intensity and averaged sensor response was found to be appropriate for the EN based on conducting polymer sensors with a correlation coefficient (r) of 0.94 between calculated and measured odor intensity. However, the linear regression approach was shown to be inadequate for both ENs, which included metal oxide-type sensors. Very strong correlation (r = 0.99) between measured odor intensity and calculated odor intensity using the ANN developed were obtained for both commercial ENs. A weaker correlation (r = 0.84) was found for the experimental instrument, suggesting an insufficient number of sensors and/or not enough diversity in sensor responses. The results demonstrated the ability of ENs to measure odor intensity associated with simple mixtures of odorous compounds and suggest that ANN are appropriate to model the relationship between odor intensity measurement and EN sensor response.     

Respiratory tract retention of inhaled air pollutants: Report 1 : Mercury absorption by inhaling through the nose and expiring through the mouth at various concentrations

To study atmospheric mercury absorption in human respiratory passage-ways, mercury in expired air was measured in three different states of breathing: steady breathing, deep breathing and breath held after inspiration.In this study, air containing mercury was inhaled through the nose and expired through the mouth. The concentration of mercury in the exhaled air was determined by the technique of gold-amalgam trapping, heat vaporization, and flameless atomic absorption measurement.The subjects were 13 male adults, aged 25–62 years, and 38 cases were observed. Four different concentrations of mercury, 1–3, 4–6, 10–11, and 20–30 μg/m³ were used, and absorption for each was determined. When the concentration was 1–3 μg/m₃, the absorption was 74–92%, the average being 82.5%. At concentrations of 4–6, 10–11, and 20–30 μg/m₃, the absorption was 76.6–100%, 75.5–99.2%, and 79.9–95.9% respectively, and the average was 88.8%, 85.2%, and 87.7% respectively.A slightly higher rate of mercury absorption was observed in deep breathing than in steady breathing, and when expiration was suppressed for some time after inspiration, the rate increased remarkably to 97.4–99.7%. Prolonged retention of inhaled air containing mercury in the respiratory tract is believed to have caused the increased absorption.     

The Pioneers

Abstract

This study surveyed emissions from 2- and 4-stroke new and in-use motorcycles. Emission tests were carried out on a dynamometer following the designated test procedure of the Economic Commission for Europe (ECE). Samples were derived during various driving stages, which included idle, acceleration, 30 km/hr cruise, 50 km/hr cruise, and deceleration. All test motorcycles (10 new and 15 in-use) complied with Taiwan Environmental Protection Administration’s Phase III Motorcycle Emission Standards. The dominant volatile organic carbon (VOC) species were isopentane (53 and 295 mg/km, 2- and 4-stroke, respectively), 2-methylpentane (75 and 83 mg/km), 3-methylpentane (34 and 66 mg/km), and toluene (30 and 100 mg/km). The VOC emission factors for the 2-/4-stroke motorcycles were 311/344 (new) and 1479/433 (inuse) mg/km, respectively. In addition, the dominant carbonyl species for the new and in-use motorcycles were formaldehyde (0.4 and 0.7 mg/km, respectively), acetaldehyde (0.6 and 1.2 mg/km), and acetone (0.5 and 0.7 mg/km). The carbonyl compound emission factors for the 2- and 4-stroke motorcycles were 3.2/3.1 (new) and 5.3/4.6 (in-use) mg/km, respectively. The ozone formation potentials, based on an ECE test cycle, show that the values from the in-use motorcycles were higher than those from the new motorcycles. The dominant VOC species for the ozone formation potential were propylene (65 and 502 mg-O₃ /km, respectively), isopentane (98 and 501 mg-O₃ /km), 2-methylpentane (152 and 167 mg-O₃ /km), 3-methylpentane (79 and 253 mg-O₃ /km), and toluene (127 and 398 mg-O₃ /km). Further, the dominant carbonyl species were formaldehyde (4.1 and 6.2 mg-O₃ /km, new and in-use, respectively) and acetaldehyde (4.8 and 9 mg-O₃ /km).     

Using The Consultant

The information on this page is reprinted with permission from “Guide for Professional Engineers’ Services”, published by the Professional Engineers in Private Practice Division of the National Society of Professional Engineers. The publication was designed “as a guide for selecting and engaging professional engineers in private practice and compensating them for their services”. It is available from the National Society of Professional Engineers, 2029 K Street, N.W., Washington, D.C. 20006.     

The prevention principle

Environmentally sound manufacture does not have its source only in developing and improving the techniques for treating solid, liquid and gaseous wastes at the end of the production process. Our experience shows that more effort and capital budgets must be devoted to developing preventive measures. Although the treatment techniques have become very advanced and meet ecological requirements to a very high degree, they are now reaching the limits of their technological and economic feasibility. Environmental protection at the production site has undergone structural change in recent years. The emphasis has shifted to preventive techniques which affect the production process itself, avoiding the emergence of waste at the “end of the pipe” by preventing its formation or recycling it straight away. This integrated approach is in harmony with the demands of sustainable production. The functions of in-process environmental protection measures need to be looked at as a whole from the points of view of both environmental protection and cost-effectiveness. Some integrated methods are described.     

The bait-lamina test

A general introduction of the bait-lamina test has been made in this article. This article has an introductional character for other articles dealing with the bait-lamina test method and gives the experimental data. The test was first introduced by Törne in 1990 to measure the biological activity of soil. It enables the monitoring of biotic (microbial and zootic) processes in the soil within a short period of time, and detailed investigations. The test system is based on visual assessment of feeding on small portions of thin laminated bait substrate exposed to edaphic processes. The test system has found its application mainly in Germany but in the meanwhile also in Portugal, Switzerland and in the Netherlands in laboratories of soil ecology and soil ecotoxicology. At present there are only few publications in the international literature, but the interest in this method is growing. During the past years two workshops on the subject have been organized in Germany to summarize experiences with and to evaluate the test system and optimize the standard procedure.