Odors emission

Subjective evaluation of odor emission is made difficult by the phenomenon of odor fatigue, which means that after persons have been initially subjected to an odor, they lose the ability to perceive the continued presence of low concentrations of that odor. Therefore, all systems of subjective odor evaluation rely on preventing olfactory fatigue by letting the observer breathe odor-free air for a sufficient time prior to breathing the odorous air and evaluating its odor content. Usually an activated charcoal bed is... 

Discuss the means for determining the strength of an odorous emission from a source and of definitively relating the odor to the presumed source. 

Mobile sources include railroad locomotives, marine vessels, aircraft, and automotive vehicles. Over the past 100 years, we have gained much experience in regulating smoke and odor emission from locomotives and marine craft. Methods of combustion equipment improvement, firefighter training, and smoke inspection for these purposes are well documented. This type of control is best at the local level. 

Other industries of interest are (1) the manufacturing of spices and flavorings, which may use activated carbon filters to remove odors from their exhaust stream (2) the tanning industry, which uses afterburners or activated carbon for odor removal and wet scrubbers for dust removal and (3) glue and rendering plants, which utilize sodium hypochlorite scrubbers or afterburners to control odorous emissions. 

Odorous emissions from industrial and other plants have become of greater concern also in Norway the last decades. 

Water Reclamation Works by their very nature can, at times be the source of unpleasant odorous emission. The odour-intensive compounds (osmogenes) which make up these emissions are believed to arise mainly as the decomposition products of carbohydrates and proteins. The breakdown of this waste material proceeds by aerobic and anaerobic processes at various stages of the treatment plant. Atmospheric pollution of this nature frequently results in complaints from members of the public either resident, or perhaps employed in the vicinity of such works. In order to confirm or deny that a reclamation works is responsible for a particular nuisance and, if possible to identify the causal agents it was decided that the Authority should have the capability of analysing for odorous and other polluting constituents of the atmosphere. This paper describes the progress made towards this objective and summarises the experience gained with a procedure in use. There are two principle approaches available for the analytical classification of odorous emissions -... 

Physico-chemical methods, the ultimate aim of which is to determine the exact qualitative and quantitative composition of an odorous emission. 

The only odour-intensive species conclusively identified in the odorous emission of water reclamation works were dimethyl -disulphide, -trisulphide and -tetrasulphide. 

The malodorous emission in this case appears to be dominated by volatile fatty acids and cresol. It is interesting to note in passing that cresol is one of the few odour-intensive species found in almost all odorous emission so far encountered. This osmogene is usually present in sufficient quantities to be clearly detectable of the odour port. Cresol and phenol (only found occasionally) is reported to be formed by the decomposition ol lignin. 

This sample is included because it is an interesting departure from the odorous emissions more commonly associated with water reclamation works. Aqueous dairy waste sampled at this time and subsequently analysed by the same techniques demonstrated that none ol the listed osmogenes were present. The odorous emission was thus a function of the filtration unit and its mode of operation rather than directly originating from the effluent being treated. The key osmogenes are believed to be -... 

Geosmin, 2-Methyl isobomeol (MIB) and 2-isopropyl methoxy pyrazine are known to be produced by various types of actinomycete cultures (10-15). Geosmin and MIB are saturated tertiary alcohols and resist oxidation. The steric configuration of the hydroxyl and methyl groups in both compounds are believed to interact with receptors in the nose, imparting their characteristic earthy odour (16). The four compounds itemised as the key osmogenes in this odorous emission have extremely low odour threshold concentrations. Their occasional occurence in drinking water can lead to widespread complaints and are routinely monitored for within this Authority. 

The only disadvantage inherent in the technique is that it takes no account of possible synergistic interaction between the osmogenes that constitute an odorous emission. Technical limitations which may be improved upon are thought to be -... 

A study on the effects of insulating broiler house floors to reduce odour emission levels and improve broiler carcass quality indicated that there was an improvement to the concentration of odour emissions for four weeks, then a decline to odorous emissions. Carcass quality was much improved by insulating floors. The study will continue to... 

An animal can control release of odor molecules from body surfaces, especially skin gland areas, up to a point. But in moist air, volatiles from secretions on skin or hair will evaporate more easily. If only intermittent odor emission is desirable, humidity would interfere with the animal s odor release. Glands that produce such intermittent signals, such as alarm odors, appear to be more developed in species or subspecies in drier climates. An example is the metatarsal gland in... 

To calculate the active space, the investigator needs to measure odor emission rate, detection threshold of the animal, and wind speed. 

Less evident is the primary function of plant odor emissions. Although it is clear that plant odors are used by parasitoids (Fig. 2.3) and predators to locate potential prey (Vinson et al., 1987 Nordlund et al., 1988 Whitman, 1988), they are likely to have other functions as well (Harrewijn et al, 1995 Turlings and Benrey, 1998). 

Other ecological consequences of induced odor emissions... 

Conclusive held evidence has been obtained with the manipulation of odor emissions of free-standing plants. Thaler (1999), for example, observed an increase in parasitism of S. exigua larvae on tomato after the plants had been treated with JA. This treatment induces the octadecanoid pathway, which results in the production of various defense compounds, including volatiles. In an earlier study in a tobacco held, De Moraes et al. (1998) had already found that the specialist parasitoid... 

How does pathogen infestation affect odor emissions and does it interfere with emissions induced by insect herbivores So far, only one study has specifically looked at this cross-effect (Cardoza et al, 2002). It showed that insect feeding (beet armyworm, S. exigua) and fungus infection (white mold, Sclerotium rolfsii) resulted in distinctly different odor blends in peanut plants, whereas plants that were simultaneously infested by these two antagonists released a mix of both blends. 

Knudsen, H.N., Clausen, P.A., Wilkins, C.K. and Wolkoff, P. (2007) Sensory and chemical evaluation of odorous emissions from building products with and without linseed oil. Building and Environment, 42 (12), 4059-67. 

Ruby MG, Prokop WH, Kalman DA. 1987. Measurement of odor emissions from a sewage treatment plant. Proc APCA Annu Meet 80 87/75A.4 16. 

Contents indude chemical constituents, microbiology, odor emissions, sludge processing, landfilling, incineration, land application, and public relations. 

Manufacture of new high-solids enamel for automotive coatings reduces volatile organic compound emissions, reduces odor emissions by 86%, and reduces total raw materials use by 20% (U. Chowdhry) ... 

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