污泥处置堆肥发酵仓气体数值模拟及减少臭气扩散分析

污泥的处理处置已成为城市污水处理的重要问题之一。为研究堆肥发酵仓臭气收集规律,运用计算流体力学方法对发酵仓气体环境进行了数值模拟,并对模拟结果进行了比较分析。得到了仓内气体温度及压力规律并分析了排气口布置对转仓机出口上部气体流速的影响。结果表明,温度对厂房内气流影响不容忽视,同时发酵仓排气口排气量比重向进料端倾斜的方案可增强厂房的相对封闭性。     

香气的分维

本文用分形数学理论解释调香行为,计算了香精主题香气奇怪吸引子的分维,总结出“分维越接近1,香精的主题香气就越突出”的结论。通过一系列的计算确认配制香精时用较多种相关香料的有利之处。文中也讨论了香料中“杂气”对主题香气的影响。     

咸味香料（上）

本文综述了咸味香料化合物的结构、香气和应用。     

Detection and Discrimination of Mixed Odor Strands in Overlapping Plumes Using an Insect-Antenna-Based Chemosensor System

Olfactory signals, a major means of communication in insects, travel in the form of turbulent odor plumes. In terrestrial environments, an odor blend emitted from a single point source exists in every strand of the plume, whereas, in confluent plumes from two different odor sources, the strands have some chance of being coincident and comprising a new third odor in those strands. Insects have the ability to detect and interpret necessary olfactory information from individual filamentous odor strands in complex multifilament odor plumes. However, behaviorists have had no way to measure the stimulus situations they are presenting to their temporally acute insect subjects when performing Y-tube olfactometer or confluent pheromone plume wind tunnel assays. We have successfully measured the degree of plume-strand mixing in confluent plumes in a wind tunnel by using a multichannel insect-antenna-based chemosensor. A PC-based computer algorithm to analyze antennal signals from the probe portion of the system performed real-time signal processing and, following a short training session, classified individual odorant/mixture strands at sub-second temporal resolution and a few tens of millimeters of spatial resolution. In our studies, the chemosensor classified a higher frequency of strands of two different odorants emitted from two closely spaced filter papers as being “mixed” when the sources were located only 1 or 2 cm apart than when the sources were 5 or 10 cm apart. These experiments demonstrate the chemosensor’s potential to be used for measuring odor stimulus situations in more complex multiple-plume environments.     

Mobilization of short-term memory capacity for odors in discriminative tests: implication for assessors'' selection

The objective was to determine whether individual short-term memory capacities for odor are related to performance at discriminative tests. Two groups of 11 subjects were formed with different short-term memory for odor but equivalent sensitivity toward benzaldehyde, the aromatic compound to be detected in discriminative tests. The subject sensitivity was determined by d^′ values, derived from a detection task. Memory span for odors was the largest number of odors memorized at once. It ranged from 1 to 3 for the low memory span group and from 5 to 7 for the high memory span group. Then, subjects performed 20 triangle tests and 12 2-out-of-5 tests with two strawberry flavored soft drinks, one being supplemented with benzaldehyde. Results showed that the high memory span group outperformed the low memory span group for both tests. This indicates that short-term memory ability along with sensitivity contribute to individual performance in discriminative tests. This result has implications for test design and subject selection.     

Spatial distribution of odors in simulated benthic boundary layer flows

Many animals orient to odor sources in aquatic habitats where different flows and substrates affect the hydrodynamics of benthic boundary layers. Since the dispersal of chemicals is due to the fluid mechanics of a particular environment, we quantified the changes in the fine structure of an odor plume under different hydrodynamic conditions in the benthic boundary layer of a laboratory flume. We sampled turbulent odor plumes at 10 Hz using a microchemical sensor (150 µm diameter) under two flow speeds: 3.8 and 14.4 cm/sec, and at 1, 8, 50 mm above the substrate. These distances above the substrate occur within different flow regions of the boundary layer and correlate with the location of crustacean chemosensory appendages within boundary layer flows. The high flow velocity exhibited a greater level of turbulence and had more discrete odor pulses than the low flow velocity. In general, odor signals showed a high level of temporal variation in fast flow at heights 1 and 8 mm above the substrate. In slow flow, temporal variation was maximal at 50 mm above the substrate, exhibiting more variance than the same height at the fast flow. These patterns of odor signals resulted in part from differences in the height above the substrate of the main axis of the odor plume at the two flow speeds. Our results imply that animals chemically orienting to an odor source will need to compensate for varying hydrodynamic properties of odor transport and dispersal. The method by which animals extract spatial information from odor plumes will need to account for changing flow conditions, or else it will not be equally efficient in extracting information about chemical spatial distributions.     

Are We Measuring the Relevant Indoor Pollutants?

Abstract Concentrations of volatile organic compounds (VOCs) measured indoors may exceed their odor thresholds, but are usually far below TLV estimates. Even applying additivity to eye and airway irritation effects, it is difficult to rationalize increased sick building syndrome (SBS) symptoms by exposure to generally chemically inert VOCs in the indoor environment. Several studies suggest that chemical reactions in indoor air are linked with SBS symptoms and the examination of these reactions may be necessary in order to understand the role of VOCs as causative agents of SBS symptoms. The usual evaluation of odor annoyance of VOCs based on odor thresholds should be modified, taking into account the large variation of individual human odor thresholds for single substances, and specific additivity phenomena even at subthreshold levels of VOCs. The conclusion of this review is that chemical reactions between oxidizable VOCs and oxidants, such as ozone and possibly nitrogen oxides, can form irritants which may be responsible for the reported symptoms. Compounds adsorbed to particles may also contribute to SBS symptoms. The individual effects of indoor pollutants may act in concert with temperature and relative humidity. New analytical methods are required to measure the oxidative and reactive species or specific markers thereof in indoor air.     

Simultaneous removal of odor and particulate using plasma-treated polymer filters

Polymer filters treated by plasma-assisted graft polymerization (PG), nonthermal plasma (NTP) and PG followed by NTP treatment are developed for use as multifunctional filters that can simultaneously remove odor and particulate. A NTP-treated filter can adsorb a large amount of a typical odor component, ammonia (NH₃). However, the performance of the NTP-treated filter deteriorates significantly after one month whereas that of a PG followed by NTP-treated filter deteriorates only slightly. The particulate collection efficiency of a both-side PG-treated filter is higher than that of an untreated filter whereas that of the NTP-treated filter is slightly lower.     

Anaerobically digested biosolids odor generation and pathogen indicator regrowth after dewatering

The objective of this research was to investigate whether a preferential stimulation of microorganisms in anaerobically digested biosolids can occur after dewatering and if it can lead to pathogen indicator regrowth and odor generation upon storage. Laboratory incubation simulating biosolids storage indicates that both odorant generation, based on total volatile organic sulfur compound concentrations (TVOSCs) and pathogen indicator regrowth, based on fecal coliform densities follow similar formation and reduction patterns. The formation and reduction patterns of both odor compounds and fecal coliforms imply that groups of microorganism are induced if shearing disturbance is imposed during dewatering, but a secondary stabilization can be achieved soon after 1-2 weeks of storage. The occurrence of the induction is likely the microbial response to substrate release and environmental changes, such as oxygen, resulting from centrifuge shearing. The new conditions favor the growth of fecal coliforms and odor producing bacteria, and therefore, results in the observed fecal coliforms regrowth and odor accumulation during subsequent storage. However, when both substrate and oxygen deplete, a secondary stabilization can be achieved, and both odor and fecal coliforms density will drop.     

Efficacy of using multiple open-path Fourier transform infrared (OP-FTIR) spectrometers in an odor emission episode investigation at a semiconductor manufacturing plant

This study evaluated the efficacy of simultaneously employing three open-path Fourier transform infrared (OP-FTIR) spectrometers with 3-day consecutive monitoring, using an odor episode as an example. The corresponding monitoring paths were allocated among the possible emission sources of a semiconductor manufacturing plant and the surrounding optoelectronic and electronic-related factories, which were located in a high-tech industrial park.There was a combined total odor rate of 43.9% for the three monitoring paths, each comprised of 736 continuous 5-minute monitoring records and containing detectable odor compounds, such as ammonia, ozone, butyl acetate, and propylene glycol monomethyl ether acetate (PGMEA). The results of the logistic regression model indicated that the prevailing south wind and the OP-FTIR monitoring path closest to the emission source in down-wind direction resulted in a high efficacy for detecting odorous samples with odds ratios (OR) of 3.8 (95% confidence interval (CI): 2.9-5.0) and 5.1 (95% CI: 3.6-7.2), respectively. Meanwhile, the odds ratio for detecting ammonia odorous samples was 7.5 for Path II, which was downwind closer to the possible source, as compared to Path III, downwind far away from the possible source. PGMEA could not be monitored at Path II but could be at Path III, indicating the importance of the monitoring path and flow ejection velocities inside the stacks on the monitoring performance of OP-FTIR. Besides, an odds ratio of 5.1 for odorous sample detection was obtained with south prevailing wind comprising 65.0% of the monitoring time period.In general, it is concluded that OP-FTIR operated with multiple paths simultaneously shall be considered for investigation on relatively complicated episodes such as emergency of chemical release, multiple-source emission and chemical monitoring for odor in a densely populated plant area to enhance the efficacy of OP-FTIR monitoring.