Nature of Odor Components in Diesel Exhaust

Offensive exhaust odors are characteristic of diesel engines. One problem in control and reduction of odor is lack of understanding of odorant sources and mode of formation. The solution of this problem depends on identification of the odorants so that study of their formation and control can be undertaken. A human panel performed odor assessments in studying raw and modified diesel exhaust and synthetic blends representing portions of diesel exhaust. Their assessments were used in determining odorant identity and quantitative contribution to exhaust odor. Low molecular weight aldehydes appear to contribute little to diesel odors. The sulfur and nitrogen oxides have been examined as odorants but of these apparently only nitrogen dioxide is a potential odor contributor.     

Effect of incineration on the removal of key offensive odorants released from a landfill leachate treatment station (LLTS)

As a basic means to control odorants released from a landfill leachate treatment station (LLTS), effluents venting from this station were treated via incineration with methane rich landfill gas (at 750 °C). A list of the key offensive odorants covering 22 chemicals was measured by collecting those gas samples both before and after the treatment. Upon incineration, the concentration levels of most odorants decreased drastically below threshold levels. The sum of odorant intensities (SOIs), if compared between before and after incineration, decreased from 6.94 (intolerable level) to 3.45 (distinct level). The results indicate that the thermal incineration method can be used as a highly efficient tool to remove most common odorants (e.g., reduced sulfur species), while it is not so for certain volatile species (e.g., carbonyls, fatty acids, etc.).     

Characterization of livestock odors using steel plates, solid-phase microextraction, and multidimensional gas chromatography-mass spectrometry-olfactometry

Livestock operations are associated with emissions of odor, gases, and particulate matter (PM). Livestock odor characterization is one of the most challenging analytical tasks. This is because odor-causing gases are often present at very low concentrations in a complex matrix of less important or irrelevant gases. The objective of this project was to develop a set of characteristic reference odors from a swine barn in Iowa and, in the process, identify compounds causing characteristic swine odor. Odor samples were collected using a novel sampling methodology consisting of clean steel plates exposed inside and around the swine barn for < or =1 week. Steel plates were then transported to the laboratory and stored in clean jars. Headspace solid-phase microextraction was used to extract characteristic odorants collected on the plates. All of the analyses were conducted on a gas chromatography-mass spectrometry-olfactometry system where the human nose is used as a detector simultaneously with chemical analysis via mass spectrometry. Multidimensional chromatography was used to isolate and identify chemicals with high-characteristic swine odor. The effects of sampling time, distance from a source, and the presence of PM on the abundance of specific gases, odor intensity, and odor character were tested. Steel plates were effectively able to collect key volatile compounds and odorants. The abundance of specific gases and odor was amplified when plates collected PM. The results of this research indicate that PM is major carrier of odor and several key swine odorants. Three odor panelists were consistent in identifying p-cresol as closely resembling characteristic swine odor, as well as attributing to p-cresol the largest odor response out of the samples. Further research is warranted to determine how the control of PM emissions from swine housing could affect odor emissions.     

A Comparison of Various Sources of Automotive Emissions

Chlorinated phenolic hydrocarbons are used as intermediate chemicals in the manufacture of 2,4-D (2,4-Dichlorophenoxy-acetic Acid) and related herbicides. These chemicals have an unusual odor with an extremely low threshold level of detection and consequently the manufacture and handling of these compounds poses a difficult odor control problem. Chipman Chemical Company at its Portland, Oregon plant has developed a system of fume collection and caustic soda solution scrubbing capable of removing phenolic compounds in the plant exhaust air to an acceptable level from an odor release standpoint. This article describes the development, present status, and projected future improvements of this odor control system.     

基于SPECIATE数据库的典型行业挥发性有机恶臭物质筛选

恶臭物质成分复杂、来源广泛,故需要筛选并优先控制恶臭物质。基于美国SPECIATE数据库,选取涂料、垃圾填埋、污水处理、纸浆和造纸、石油炼制、堆肥、合成橡胶和合成树脂共8类典型行业,以质量分数、嗅阈值、饱和蒸气压和大气周围环境目标值为评估参数,建立合适的筛选原则、程序和方法。通过分级赋值和多参数综合评分筛选出84种(类)典型行业挥发性有机恶臭物质。结合国内外标准和研究,建议将苯乙烯、丙醛、丙酸、丁醛、丁酸、二甲苯、二甲基二硫醚、二硫化碳、甲苯、甲基乙基酮、甲基异丁基酮、甲硫醇、甲硫醚、戊醛、戊酸、乙醛、乙酸丁酯、乙酸乙酯和异丁醇,共19种(类)物质作为优先控制挥发性有机恶臭物质,以作为监控管理、评估空气异味和标准制修订的参考。     

Characterization of odor released during handling of swine slurry: Part I. Relationship between odorants and perceived odor concentrations

Odor emission from livestock production systems is a major nuisance in many rural areas. This study aimed at determining the major airborne chemical compounds responsible for the unpleasant odor perceived in swine facilities during slurry handling, and at proposing predictive models of odor concentration (OC) based on the concentrations of specific odorants in the air. A multivariate data analysis strategy involving principal components analysis and multiple linear regressions was implemented to analyze the relationships between concentration of 35 gases (measured by GC/MS or gas detection tubes), and the overall OC perceived by sensory analysis. The study compiled data on the concentration of odor and odorants, measured in the headspace of 24 unstored and stored slurry samples collected from three different types of production units on 8 commercial swine farms. Among all the measured constituents, OC was found to have the highest correlation with the sulfur containing compounds (i.e. hydrogen sulfide, dimethylsulfide, dimethyldisulfide, dimethyltrisulfide). The concentration of hydrogen sulfide accounted for 68% of the variation in OC above the stirred slurry samples. The highest concentrations of volatile organic compounds were observed for phenols and indoles, which made a significant contribution to the overall OC when the slurry was fresh. The contribution of ammonia to the OC was only significant in the absence of hydrogen sulfide. The precision of predictive models of OC based on the concentration of specific odorants in the air was satisfactory (R² between 0.66 and 0.89). Hence, this study suggests that monitoring of specific odor compounds released from agitated swine slurry can be used to predict the concentration of odor perceived close to the source (e.g. at storage units), allowing the assessment of odor nuisance potentials.     

Dispersion modeling to compare alternative technologies for odor remediation at swine facilities

The effectiveness of 18 alternative technologies for reducing odor dispersion at and beyond the boundary of swine facilities was assessed in conjunction with an initiative sponsored through agreements between the Attorney General of North Carolina and Smithfield Foods, Premium Standard Farms, and Frontline Farmers. The trajectory and spatial distribution of odor emitted at each facility were modeled at 200 and 400 m downwind from each site under two meteorological conditions (daytime and nighttime) using a Eulerian-Lagrangian model. To predict the dispersion of odor downwind, the geographical area containing the odorant sources at each facility was partitioned into 10-m2 grids on the basis of satellite photographs and architectural drawings. Relative odorant concentrations were assigned to each grid point on the basis of intensity measurements made by the trained odor panel at each facility using a 9-point rating scale. The results of the modeling indicated that odor did not extend significantly beyond 400 m downwind of any of the test sites during the daytime when the layer of air above the earth's surface is usually turbulent. However, modeling indicated that odor from all full-scale farms extended beyond 400 m onto neighboring property in the evenings when deep surface cooling through long-wave radiation to space produces a stable (nocturnal) boundary layer. The results also indicated that swine housing, independent of waste management type, plays a significant role in odor downwind, as do odor sources of moderate to moderately high intensity that emanate from a large surface area such as a lagoon. Human odor assessments were utilized for modeling rather than instrument measurements of volatile organic compounds (VOCs), hydrogen sulfide, ammonia, or particulates less than 10 microm in diameter (PM10) because these physical measurements obtained simultaneously with human panel ratings were not found to accurately predict human odor intensity in the field.     

Using olfactometry to measure intensity and threshold dilution ratio for evaluating swine odor.

Intensity and threshold dilution ratio are two important indices for odor control of swine buildings. Although odor threshold dilution ratio is a widely used index to describe an odor, it should be related to intensity to be more useful. A method was proposed to measure both indices simultaneously by using a dynamic forced-choice olfactometer. Four air samples were taken from each of four swine rooms including farrowing, finisher, gestation, and nursery. A panel of eight people was used to evaluate odor intensity. Odor threshold dilution ratios were calculated according to the American Society for Testing and Materials (ASTM) Standard Practice E679-91 to be 333, 424, 25, and 221 for samples collected from farrowing, finisher, gestation, and nursery rooms, respectively. After the samples were diluted 14.7 times, the odor intensities were evaluated to be 3.79, 3.46, 0.48, and 4.0 for the above-mentioned rooms, respectively. The data collected were used to develop a mathematical model.     

Using Olfactometry to Measure Intensity and Threshold Dilution Ratio for Evaluating Swine Odor

ABSTRACT

Intensity and threshold dilution ratio are two important indices for odor control of swine buildings. Although odor threshold dilution ratio is a widely used index to describe an odor, it should be related to intensity to be more useful. A method was proposed to measure both indices simultaneously by using a dynamic forced-choice olfacto-meter. Four air samples were taken from each of four swine rooms including farrowing, finisher, gestation, and nursery. A panel of eight people was used to evaluate odor intensity. Odor threshold dilution ratios were calculated according to the American Society for Testing and Materials (ASTM) Standard Practice E679-91 to be 333, 424, 25, and 221 for samples collected from farrowing, finisher, gestation, and nursery rooms, respectively. After the samples were diluted 14.7 times, the odor intensities were evaluated to be 3.79, 3.46, 0.48, and 4.0 for the above-mentioned rooms, respectively. The data collected were used to develop a mathematical model.     

Community Response to Environmental Noise

A portable 1-butanol olfactometer was developed for quantifying odors in ambient air. Panelists compare the intensity of ambient odors with the intensity of discrete levels of 1-butanol provided by the olfactometer. Range of delivered 1-butanol concentrations Is 0 to 80 ppm in air at a flow rate of 15 L/min. Laboratory tests were performed to ascertain overall precision, consistency of panelist responses, uniqueness of each odor step, variability between two Identical olfactometers, and effect of delivery method. For 855 pairs of matched odor Intensities, the ratio of measured butanol concentration to set concentration averaged 0.984 or —0.023 scale steps (where the scale steps differ In concentration by factors of two). In field experiments the equivalent ambient odor Intensities determined by odor panels using the butanol olfactometer ranged from 1.5 ppm to 64 ppm of 1-butanol vapor In air. The precision of ambient odor measurements was within one-half scale step on the 1-butanol olfactometer, sufficient for most odor investigation and abatement research applications.     

Filters and Filter Media for the Cement Industry

To correlate the odor strength of natural gas with its sulfur analysis, the recognition odor thresholds of 18 sulfur compounds were determined using an untrained panel of 35 peopie. For each test a series of odor concentrations graduated in increments of 10^0.2 was presented to the panel in random order over a range of concentrations above and below the olfactory thresholds of all panelists. Each odor was tested on at least three different days. Desired odor concentrations were produced by dynamic blending of gaseous mixtures of the odorous compounds with air. All testing was done out-of-doors during clement weather when no ambient odors were apparent. The range of olfactory response was found to be much greater for certain compounds than for others. Branching of the hydro-carbon chain increased odor strength. Certain compounds appeared to evoke anomalous responses.     

Development of the Relationship between Odor Intensity and Threshold Dilution Ratio for Swine Units

ABSTRACT

The following models of odor intensity for swine units were evaluated: the Weber-Fechner law model, the power law model, the Stevens model, and the Beidler model. Data were collected from four swine rooms (farrowing, finisher, gestation, and nursery) and odor threshold dilution ratios were measured by a panel using a dynamic forced-choice olfactometer. Odor intensity scales were determined by eight panelists using a six-point category scale method. A nonlinear parameter estimation method was used to estimate the parameters in each of the models. The widely used Weber-Fechner law did not adequately fit the data of odor intensity and threshold. Both the power law and the Beidler models described the data effectively, but the Beidler model showed the best fit of the data and was used as the model to represent the relationship between odor intensity and threshold dilution ratio for swine buildings.     

餐厨垃圾两相厌氧发酵产甲烷相恶臭排放规律

为了研究餐厨垃圾两相厌氧发酵产甲烷相恶臭排放规律,在中温（35℃）条件下,以餐厨垃圾为发酵底物进行中试规模的两相连续式厌氧发酵试验,并对一个周期内不同时间段产甲烷相产生的气体进行采样,分析其臭气浓度和物质浓度,结合各组分的阈稀释倍数,筛选出主要的恶臭污染物。结果表明,在发酵系统稳定运行阶段,产甲烷相产生的臭气浓度较大,都在23万以上;产甲烷相产生的恶臭物质主要包括硫化物、萜烯类、含氧类和芳烃类四类化合物,其中质量浓度最高的恶臭物质是硫化氢,超过了150 mg/m3;产甲烷相的主要致臭物质是硫化物,其中贡献最大的是硫化氢,其阈稀释倍数都在26万以上,其次为乙硫醇﹥甲硫醇﹥乙硫醚,这3种物质的阈稀释倍数都在4 000以上;除了这4种硫化物,丁醛对恶臭的贡献也比较大,其阈稀释倍数也在4 000以上。     

Sensory and chemical characterization of VOC emissions from building products: impact of concentration and air velocity

The emissions from five commonly used building products were studied in small-scale test chambers over a period of 50 days. The odor intensity was assessed by a sensory panel and the concentrations of selected volatile organic compounds (VOCs) of concern for the indoor air quality were measured. The building products were three floor coverings: PVC, floor varnish on beechwood parquet and nylon carpet on a latex foam backing; an acrylic sealant, and a waterborne wall paint on gypsum board. The impacts of the VOC concentration in the air and the air velocity over the building products on the odor intensity and on the emission rate of VOCs were studied. The emission from each building product was studied under two or three different area-specific ventilation rates, i.e. different ratios of ventilation rate of the test chamber and building product area in the test chamber. The air velocity over the building product samples was adjusted to different levels between 0.1 and 0.3 m s^-1. The origin of the emitted VOCs was assessed in order to distinguish between primary and secondary emissions. The results show that it is reasonable after an initial period of up to 14 days to consider the emission rate of VOCs of primary origin from most building products as being independent of the concentration and of the air velocity. However, if the building product surface is sensitive to oxidative degradation, increased air velocity may result in increased secondary emissions. The odor intensity of the emissions from the building products only decayed modestly over time. Consequently, it is recommended to use building products which have a low impact on the perceived air quality from the moment they are applied. The odor indices (i.e. concentration divided by odor threshold) of primary VOCs decayed markedly faster than the corresponding odor intensities. This indicates that the secondary emissions rather than the primary emissions, are likely to affect the perceived air quality in the long run. Some of the building products continued to affect the perceived air quality despite the concentrations of the selected VOCs resulted in odor indices less than 0.1. Therefore, odor indices less than 0.1 as an accept criterion cannot guarantee that a building product has no impact on the perceived air quality.     

抗生素发酵制药工程中异味的特征与关键污染物识别

抗生素原料药在生产过程中产生异味污染引发的民众投诉增多,逐渐成为发酵制药企业亟需解决的污染治理难点。以红霉素、四环素和泰乐菌素3种抗生素原料药的发酵生产过程为例,通过采用感官评价、电子鼻、气相离子迁移谱和气相质谱等多手段分析方法,解析发酵过程中产生的异味污染特征。结果表明：3种发酵尾气的气味特征、挥发性物质组分和含量差异较大;尾气中含有的挥发性物质有相同的组分,如乙醇、丙酮、2-戊酮、辛醛和苯甲醛,也各有特异性成分。未经处理的红霉素发酵尾气具有明显的土霉味,且臭气浓度值明显大于四环素和泰乐菌素发酵尾气。气味活度值(OAV)的计算结果表明：2-MIB和土臭素2种萜烯类物质是红霉素发酵最主要的异味污染物;而四环素和泰乐菌素的发酵异味是多种醛等含氧有机物和有机硫化物混合后形成的,因而气味特征较复杂。3种废气中,红霉素发酵尾气具有气量大、异味物质嗅阈值极低的特点,易造成异味污染且影响范围广,去除治理的技术难度也相对更大。本研究通过解析识别不同品种抗生素的发酵异味污染特征,以期为抗生素发酵异味污染治理和环境管理提供参考。     

On the Determination of Odor Thresholds in Air Pollution Control—An Experimental Field Study on Flue Gases from Sulfate Cellulose Plants

From the hygienic point of view, not only the health hazards caused by air pollutants but also the odor from emitted flue gases should be reduced to a minimum. An effective control of the risk of odor at ground level presupposes knowledge of the source concentration of the odoriferous gas as well as its odor threshold. This threshold has to be estimated empirically, as the flue gases often contain a complex mixture of different odoriferous substances, the odor thresholds of which are in most cases unknown. For this purpose a method has been developed for estimating the odor thresholds of flue gases emitted, from different industrial processes. The method, afield method, is based on an exposure procedure, a number of subjects compare different concentrations of the flue gas with samples of fresh air and decide at what concentration the flue gas is no longer noticeable. The gas samples used are neither compressed, nor absorbed or heated before the exposure test. The method has been used in two studies on gases from Swedish sulfate cellulose plants. In order to estimate the effect on the odor threshold of different deodorizing measures, gas samples were taken not only from the stack but also from different phases in the production process. The results and a brief discussion on the practical applications of the method are given.     

Characterization of odor released during handling of swine slurry: Part II. Effect of production type,storage and physicochemical characteristics of the slurry

The quality of rural life can be affected by offensive odors released from animal buildings and storage units. The objectives of this study were to compare the concentrations of odor and odorants above different types of stirred swine slurry to analyze the relationships between concentrations of odor (and odorants) and physicochemical characteristics of the slurry (i.e. pH, temperature, dry matter, volatile solids, and concentration of 22 chemical compounds); and to propose predictive models for the odor concentration (OC) based on these physicochemical characteristics (solely and in combination with concentrations of specific odorants in the air above the slurries). The study comprised data on concentrations of odor and odorants in the air above slurry samples (fresh and/or stored) collected from production units with farrowing sows, finishing swines, or weaning pigs at eight swine operations (N = 48). OC measured in the air above stirred swine slurry samples were not significantly different among production types or storage times. The physicochemical characteristics of the slurries were not useful for predicting OC or concentrations of hydrogen sulfide (or organic sulfides) above the slurry, but were related to concentrations of other emitted gases such as phenols and indoles (r² = 0.65–0.79, p <0.05), ammonia (r² = 0.86, p < 0.05) and carboxylic acids (r² = 0.23–0.59, p <0.05). There was good precision of predictive models of OC based on selected slurry characteristics (i.e. pH, dry matter, nitrogen content, sulfur content or concentrations of individual aromatic compounds and carboxylic acids) together with concentrations of specific odorants in the air (e.g. hydrogen sulfide) (r² between 0.70 and 0.92). This study suggests that predictive models could be useful for evaluating odor nuisance potentials of swine slurry during handling.     

Odors and volatile organic compounds released from ventilation filters

Used supply air filters were studied by sensory and chemical methods. In addition, filter dust was examined by thermodesorption/cold trap (TCT) and headspace (HS) devices connected to a GC–MS. The prefilter was the main odor source in the ventilation unit, but when humidifier was turned on odor was released mainly from the fine filter. However, the effect of the relative humidity (RH) was only temporary. At the same time, there was an increase in the concentration of aldehydes after the filters. Aldehydes, carboxylic acids, and nitrogen-containing organic compounds were the main emission products in the thermodesorption analyses of the filter dust. Many of these compounds have low odor threshold values and, therefore, contribute to the odor released from the filters. Especially, the role of aldehydes seems to be important in the odor formation.     

Measurement of Ambient Odors Using Dynamic Forced-Choice Triangle Olfactometer

Certain odor control regulations specify use of the Scentometer for ambient odor measurement. This evaluation is usually performed by a single individual who is surrounded by the odorous environment to be measured. A method is desired where an ambient odor sample can be evaluated by an adequate size panel in an odor-free atmosphere. A dynamic forced-choice triangle olfactometer was designed and constructed to measure ambient odors. Teflon bags of 18 liter capacity collect a sample within 2-3 minutes which includes pre-flushing the bag. The sample is evaluated by a dynamic olfactometer equipped with 5 dilution levels (81×, 27×, 9×, 3× and undiluted sample). Three sniffing ports are provided at each dilution level to present dynamically one diluted odor stimulus and two odor-free air blanks. Each panelist is required to indicate which port contains the odor. Evaluation of one sample is routinely completed by a panel of 9 within less than 15 minutes. The odor threshold value (ED₅₀) for the panel is calculated by use of a simple table derived statistically. No significant loss of odor was observed in sampling and in storage of rendering odors up to 48 hours. Bags were reusable after flushing with odor-free air. Reproducibility of log ED₅₀ values by the same panel was within a σ = 0.10 log₁₀. Agreement in evaluating duplicate field samples by two different panels was within the same limits. Under controlled laboratory conditions, a Scentometer reading of D/T = 2 was equivalent to an ED₅₀ = 4.8; and D/T = 7 was equal to ED₅₀ = 9.5.     

Improvement of odor intensity measurement using dynamic olfactometry

Odor intensity reveals a dose-effect relationship between inhaled odor and perceived odor sensation by the receptors, while odor concentration reflects the odor strength at the emission sources. The study reports significant improvements in experimental procedures in establishing the odor concentration-intensity (OCI) relationships using a newly developed digital olfactometer. The improvements in experimental procedures have been made to meet the requirements of both the VDI guideline 3882.1 and the European standard (EN13725). Several areas which could affect the reliability of the results have been identified in some similar studies. The latest digital olfactometer was calibrated automatically to ensure accurate and repeatable dilution ratios. Cross contamination has been eliminated through the instrument design and extensive cleaning procedures, making random presentation possible. Stringent panelist screening and continuous performance monitoring ensures consistent sensitivity of the panel. The extension of odor intensity category to temperature sensation gives a reference to assist judgments of perceived odor sensation. The DynaScent calculation method has simplified odor intensity calculation and can be applied to many odor samples. A total of 38 odor samples from three alumina refinery sites and two sewage treatment plants were collected for analysis. The results have confirmed the efficiency of the olfactometer. Distinct Odor Concentrations (DOCs) were calculated for each sample using both VDI and DynaScent methods. A student t test on two major odor types confirmed that there are no significant differences between two methods. The study has shown the DOCs for refinery odor and wastewater odor are in the range of 3.8-15.4 and 4.2-15.6 odor unit (OU)/m3 respectively. The study demonstrated that the improvements are critical in achieving reliable odor intensity measurement. This can lead to the setup of quantitative odor impact criteria for different industries and sites.