DETERMINATION OF ODOR SOURCES FOR CONTROL
The successful solution of odor pollution problems first requires an assessment of the nature and extent of the problems. A plant or facility that emits odor from a single source (such as ii stack or vent) requires less effort than a plant with a variety of odor sources that may number in the hundreds. In the latter case, there is a need to assess the problem in such terms as to achieve maximum reduction in odor at a minimal control cost. Quantitative and accurate measurements of the various emission sources and their contribution to the odor in the ambient air must be determined in order to identify and rank the various sources that should receive priority for control. Accurate measurements of odor strength relative to concentration are also useful for defining the degree of control necessary for the single-source situation. Attempts to relate source odor measurements with ambient odors by the use of diffusion equations have met with varying degrees of success.1.2 Wohlers,l utilizing an evacuated bulb technique for sampling stack gases from a petroleum coking plant, a kralt paper mill, an anion-garlic dehydrating plant, and a rotogravure printing plant, found that odor measurements at the stacks did not agree in all cases with the calculated dilutions at the distances in the field where the odors were noted. Hogstrom2 demonstrated that a fluctuating plume dispersion model can be used to give realistic estimates of odor frequencies around a point source when the odor thresholds of the chimney gases (sulphate pulp factory) are determined by sampling and sensory methods described by Lindvall.3 Our experience in sampling and evaluating odors has indicated that existing sampling techniques such as ASTM syringe method have seriously underestimated the magnitude of odors emitted by a factor in the range of 2OO-2O,OOO.4 We believe that inadequate sampling and evaluation techniques are the major reasons for reported “failures” of dispersion estimates in predicting ambient odors. In our technique, we use trained odor chemists to carry out odor surveys of the surrounding areas to define the odor types and intensities perceived off-site and to conduct in-plant surveys to identify all significant odor sources. T o supplement this, we have developed a source-sampling detailed laboratory odor-evaluation technique to allow comparison of the various odor sources and to make use of predictions based on dispersion equations. We have observed reasonably good correlation between predicted odor intensities from the source analyses determined in the laboratory and those observed by our analysts in the field. OFF-SITE SURVEY
A Comparison of Polymer Adsorbent and Bag Sampling Techniques for Paint Bake Oven Odorous Emissions
The quantity and quality of chemical components responsible for odors that may be present in a stack effluent can be quite variable, and are often unknown. Therefore, the likelihood that a single sampling technique will be useful for all odor source assessment problems is highly improbable. This paper reports the results of a study comparing the sampling of odor emissions from automobile paint bake ovens with Chromosorb 102 and in Tedlar bags with and without predilution during bag sampling. Profile analysis of the chemical species recovered by these techniques was also performed to gain additional insight into the relative merits of each procedure. Odor presentation was performed using both the continuous dilution-tothreshold and the dose-response techniques. This study indicates that odor sampling with Tedlar bags can be a valid technique for the evaluation of stack emissions where it is known that volatile species are the primary odorants, if sufficient predilution is employed during sampling. Furtherm...
Heritage Languages: In the 'Wild' and in the Classroom
Heritage speakers are people raised in a home where one language is spoken who subsequently switch to another dominant language. The version of the home language that they have not completely acquired – heritage language – has only recently been given the attention it deserves from linguists and language instructors. Despite the appearance of great variation among heritage speakers, they fall along a continuum based upon the speakers’ distance from the baseline language. Such a continuum-based model enables researchers and instructors to classify heritage speakers more accurately and readily. This article discusses the results of research on lower-proficiency speakers, identifying recurrent features of heritage languages in phonology, morphology, and syntax. Preliminary results indicate that different heritage languages share a number of structural similarities; this finding is important for the understanding of general processes involved in language acquisition. The article also presents implications of the main findings for language education and identifies areas needing further study.