Odor Concentration Research Articles

Continuous intake of galacto-oligosaccharides containing syrup contributes to maintaining the health of household dogs by modulating their gut microbiota.

Interest is growing in the relationship of the microbiota and intestinal environment with health in companion animals. Galacto-oligosaccharides (GOS), typical prebiotics, are expected to provide benefits in dogs. Previous studies of GOS in dogs have involved dogs with similar rearing conditions and diets, which may have biased the results. We conducted an open study of 26 healthy dogs kept in households with diverse rearing environments in order to evaluate how the intake of a GOS-containing syrup affects the intestinal microbiota and its metabolites. Each dog was fed 1.2-4.8 g of the GOS-containing syrup (GOS 0.5-2.0 g equivalent) for 8 weeks. Fecal microbiota, fecal concentrations of organic acids and putrefactive products, fecal odor, and serum uremic toxin concentrations were evaluated before intake (0 weeks), during the 8-week intake period (4 and 8 weeks), and 4 weeks after intake (12 weeks). The activity of N-benzoyl-DL-arginine peptidase in dental plaque, which may be associated with periodontal disease, was evaluated at 0 and 8 weeks. Continuous intake of GOS resulted in changes in fecal microbiota, with a particularly marked increase in the abundance of Megamonas, which produces propionic acid. Other findings included a significant increase in the fecal acetic, propionic, and n-butyric acid concentrations. Additionally, significant decreases in fecal odor, fecal phenol concentration, and serum indoxyl sulfate concentration. Intake of GOS was also associated with a significant decrease in N-benzoyl-DL-arginine peptidase activity in dental plaques. These results suggest that continuous intake of GOS may contribute to canine health.

Correlation between odour and hydrogen sulphide concentrations from municipal wastewater treatment plant immissions

The study focused on odours generated by hydrogen sulphide (H2S) immissions from a municipal wastewater treatment plant in a city of 2 million people. Odour awareness was vital to monitor environmental pollution and human’s safety. H2S was released from decomposition of organic matter, sulphites (SO32-) and sulphates (SO42-) by anaerobic microorganisms used in the biological stage of wastewater treatment. H2S was responsible for odours coming from the treatment plant. Long exposure (8 hours) to 2-5 ppm causes headaches and watery eyes, and 50 ppm irritates the airways. Maximum permissible concentrations for H2S are 0.006 ppm (24 hours) and 0.011 ppm (30 minutes). In Romania there are no limits on the concentration of odours. The sludge pumping station from the wastewater treatment plant registered the highest odour concentration at 36.000 OUE/m3, with significant levels of H2S primarily found there. Nevertheless, the activated sludge aeration system effectively eliminated around 99% of the H2S through degradation and absorption processes. The correlation between H2S and odour has been proved by a direct proportional relationship with a ratio of 25.000. Experimental determinations and mathematical modelling, using the Aermod View program, contributed to a deeper understanding of the impact of odours on the environment and on sensitive receptors, showed maximum odour concentrations of 38.8 ouE/m3 at the site of the municipal wastewater treatment plant and 5 ÷7 ouE/m3 at receptors, but without affecting residential areas.

Determination of odour emission rates emitted by active area sources and dispersion of odour concentration in the surrounding air

In this study, the area of a biofilter representing an active area source was sampled by taking 12 odour samples from the gaseous effluent and measuring the physical parameters of the source, so that we can obtain the odour emission rate (OER) specific to the source. The odour sampling process is a crucial step in the assessment and monitoring of odour pollution. Direct measurement of odour concentration in the ambient air is often not sufficient to determine whether an activity is responsible for producing olfactory discomfort to the receptors. To observe the contribution of the source to olfactory pollution and air quality by estimating the odour concentration in the ambient air, the odour emission rate (OER) was taken into account, which is expressed in odour units per second (ouE/s) and is obtained as the product of the odour concentration and the airflow rate associated with the source. The odour emission rate was entered into the dispersion program AERMOD for mathematical modeling. In order to estimate the odour concentration in the surrounding air in the adjacent areas to the sampled biofilter, 2 mathematical models were made to illustrate the odour concentration on the site and in its vicinity in the most unfavorable weather conditions „Highest values” and „98th Percentile” to illustrate the concentration in the surrounding air excluding the 2% unfavorable weather condition.

Assessing the spatial distribution of odor at an urban waterfront using AERMOD coupled with sensor measurements

ABSTRACT Impressions of a place are partly formed by smell. The urban waterfronts often leave a rather poor impression due to odor pollution, resulting in recurring complaints. The nature of such complaints can be subjective and vague, so there is a growing interest in quantitative measurements of emissions to explore the causes of malodorous influence. In the present work, an air quality monitor with an H2S sensor was employed to continuously measure emissions of malodors at 1-min resolution. H2S is often considered to be the predominant odorous substance from sludge and water bodies as it is readily perceptible. The integrated means of concentration from in situ measurements were combined with the AERMOD dispersion model to reveal the spatial distribution of odor concentrations and estimate the extent of odor-prone areas at a daily time step. Year-long observations showed that the diurnal profile exhibits a positively skewed distribution. Meteorology plays a vital role in odor dispersion; the degree of dispersion was explored on a case-by-case basis. There is a greater likelihood of capturing the concentration peaks at night (21:00 to 6:00) as the air is more stable then with less tendency for vertical mixing but favors a horizontal spread. This study indicates that malodors are changeable in time and space and establishes a new approach to using H2S sensor data and resolves a long-standing question about odor in Hong Kong. Implications: this study establishes a new approach combining dispersion model with novel H2S sensor data to understand the characteristics and pattern of odor emanated from the urban waterfront in Hong Kong. The sensor has dynamic concentration range to detect the episodic level of H2S and low level at background conditions. It provides more complete information in relation to odor annoyance, as well as quantitative information useful for odor regulation

Wind Tunnels and Airflow-Driven Assays: Methods for Establishing the Cues and Orientation Mechanisms That Modulate Female Mosquito Attraction to Human Hosts.

Understanding how female mosquitoes find a prospective host is crucial to developing means that can interfere with this process. Many methods are available to researchers studying cues and orientation mechanisms that modulate female mosquito attraction to hosts. Behaviors that can be monitored with these assays include activation, taking flight, upwind flight along an odor plume (optomotor anemotaxis), close approach to the stimulus (including hovering), and landing. Video recording can three-dimensionally document flight tracks and can correlate overall distribution patterns and moment-to-moment movements with odor contact and the presence of nearby cues such as a visual target. Here, we introduce mosquito host-seeking behaviors and methods to study them: wind tunnels (which allow orientation in free-flight), airflow-driven assays (using either tethered mosquitoes or small assay chambers that permit flight but also often dictate walking orientation), and still-air assays (wherein in odor concentration and spatial distribution are the orientation cues). We also describe factors that affect the assays and provide assay design considerations.

Characterization of diffuse odorous emissions from lignocellulosic biomass storage

The use of lignocellulosic biomass for green energy production is increasing, but the wood storage may lead to ambient odor related issues. This study aims to assess the odor potential and to investigate the mechanisms that promote odorous emissions from wood chip heaps. To achieve this goal, four experimental campaigns were conducted in an Italian thermal power plant. During these campaigns, odor concentration and chemical-physical parameters, that should theoretically affect the odor potential of biomass heaps, were investigated. The first important outcome revealed a strong heterogeneity on the heaps surface, classified as dry or smoking according to the superficial humidity and smoke. Smoking areas proved to be much more emissive and at self-ignition risk than dry regions. Indeed, odor concentration on smoking regions reached values in the order of 105 ouE/m3, significantly higher than dry region ones (102 ouE/m3). In addition, the highest values of odor concentration have been detected in the first days of storage, when fatty acids are oxidized and terpenes are released. Again, after 30 ÷ 80 days, i.e. about 20 days after the temperature peak caused by biological activity, odor concentration increases, suggesting a possible cause-effect mechanism between biological processes and odor release. Unexpectedly, odor emissions decreased during summer, reasonably due to the high ambient temperature which reduces the moisture content limiting biological activity. However, after about 100 days of storage, smoking regions extent and odor emissions can be considered negligible.

A versatile odor detection system based on automatically trained rats for chemical sensing

We report a versatile odor detection system that employs rats trained through automated operant conditioning paradigms. While detection animals possess remarkable olfactory capabilities, their practical use has been limited by non-automated training methods, which involve lengthy training periods, high costs, handler dependency, and low reliability. Our primary research goal was to develop detection animals using a fully automated system. To achieve this, we employed four distinct operant conditioning approaches to train four rats (Numbers 3, 7, 10, and 12) in an automated apparatus for detecting 2,4-dinitrotoluene (DNT). Our system performed exceptionally well, with DNT-trained rats achieving a 95 % accuracy rate, 99 % sensitivity, 91 % specificity, 92 % positive predictive value (PPV), and 99 % negative predictive value (NPV) across 380 tests. Additionally, we observed a linear decrease in response time as DNT concentration increased from 20 parts per billion (ppb) to 1000 ppb, indicating the system's potential for quantitative odor concentration measurement. Impressively, the rats retained their odor discrimination skills for up to four months after their last training session, underscoring the durability of their olfactory memory. Our study introduces a novel, highly effective system for specific odorant component detection, offering a faster, more reliable, and accurate method for distinguishing between various odors.

A perspective of randomness in a clinical test of olfactory performance

Random walks describe stochastic processes characterized by a sequence of unpredictable changes in a random variable with no correlation to past changes. This report describes the random walk component of a clinical sensory test of olfactory performance. The precise definition of this stochastic process allows the establishment of precise diagnostic cut-offs for the identification of olfactory loss. Within the Sniffin`Sticks olfactory test battery, odor discrimination (D) and odor identification (I) are assessed by four- and three-alternative forced-choice designs, respectively. Meanwhile, the odor threshold (T) test integrates a three-alternative forced-choice paradigm within a staircase paradigm with seven turning points. We explored this paradigm through computer simulations and provided a formal description. The odor threshold assessment test consists of two sequential components, the first of which sets the starting point for the second. Both parts can be characterized as biased random walks with significantly different probabilities of moving to higher (11%) or lower (89%) values. The initial odor concentration step for the first phase of the test and the length of the subsequent random walk in the second phase significantly affect the probability of randomly achieving high test scores. Changing the odor concentration from where the starting point determination for the second test part begins has raised the current cut-off for anosmia, represented as T + D + I < 16, from the 87th quantile of random test scores to the 97th quantile. Analogous findings are likely applicable to other sensory tests that use the staircase paradigm characterized as random walk.

Association of the AspP298Asn polymorphism in the MC4R gene with fattening productivity of immunologically castrated and uncastrated gilts

The study was aimed at establishing the presence of MC4R (c.1426 A&gt;G) gene polymorphism among the population of immunologically castrated and native gilts (Large White × Landrace) × Maxgro. Asp298Asn polymorphism affects the economic rate of growth and fattening productivity of commercial lines of pigs. Since the polymorphism of the MC4R gene correlates with the concentration of androstenone, skatole, and indole, the possible use of polymorphism as a molecular DNA marker MC4R for genetic selection in order to reduce the level of boar odor in gilts meat and fat. This will establish which alleles and genotypes in general will be determined as desirable in the marker dilution of hybrid pigs. With this in mind, the purpose of the study was to determine the effect of the MC4R genotype on fattening performance indicators and correlation with boar odor in hybrid gilts based on population-genetic variability. Genomic DNA was isolated from the ear hair follicle of native gilts (n=42) and epithelial tissue from the ear of immunologically castrated ones (n=52). Genotyping was performed using polymorphism of the lengths of restrictive fragments (RFLP). Genetic-correlation parameters for native and immunologically castrated gilts were evaluated by ADG/AGE30 and ADG/AGE100. However, the polymorphism of the c.1426 A&gt;G gene did not significantly affect the ADG/AGE100 performance of hybrid gilts. The predominance of the frequency of allele A (0.55) is established above the frequency of the allele G (0.45). Analysis of the frequency distribution of genotypes showed the saturation of micropopulation with heterozygotes AG (0.51) with a small proportion of GG carriers (0.19). Immunologically castrated and uncastrated gilts with an MC4RA allele are characterized by a sufficiently high ADG/AGE100 and are probably characterized by a high level of boar-specific odor compared to gilts with lower ADG/AGE100 with an MC4RG allele. According to the data obtained, the desired genotype for an equilibrium of the concentration of boar odor without compromising physiological development, growth rate, and productivity formation is heterozygous offspring with the MC4RAG genotype.

Effect of peat moss as a feed additive on odorous compound concentration and odor contribution in stored pig slurry

Effect of peat moss as a feed additive on odorous compound concentration and odor contribution in stored pig slurry

SENSORIAL TECHNIQUES OF ODOUR MEASUREMENTS – A RELATIONSHIP BETWEEN ODOUR CONCENTRATION AND ODOUR INTENSITY FOR A SELECTED WASTE MANAGEMENT FACILITY

Sensory analyses are one of the most frequently used odour research methods that allowestablishing the most important odour characteristics, i.e. odour concentration and odourintensity, characterised by a high degree of interrelationship. During an11-month study odourconcentration and intensity were measured at selected mechanical-biological solid municipalwaste treatment plant at 35 measuring locations to assess the degree of correlation between thosetwo parameters. Commonly used Weber-Fechner law was applied to assess the correlation. Resultsindicate a high degree of correlation between odour concentration and intensity, for example, R2valued for two different approaches at 0.87, and 0.95, while Pearson’s r valued at 0.93, and 0.97.Following the results this proves that odour concentration and odour intensity could potentially beused interchangeably for odour assessment. However, applying Weber-Fechner law for predictionof odour concentration based on odour intensity measurements gives imprecise results. Suchapproach could be potentially applied when limited measurements of odour concentration areavailable as determination of odour intensity that could be performed even by Facility employees.

Implementation of an electronic nose for real -time identification of odour emission peaks at a wastewater treatment plant

This paper proposes a novel approach for the real-time monitoring of odour emissions from a WasteWater Treatment Plant (WWTP) using an Instrumental Odour Monitoring System (IOMS). The plant is characterized by unpredictable odour peaks at its arrival tank (AT), generating nuisance and complaints in the population living nearby the plant. Odour peaks are most likely due to the conferment of non-identified and malodorous wastewaters coming from various industrial activities. Due to the high variability of sources collecting their wastewaters to the WWTP, a new methodology to train the IOMS, based on the use of a one-class classifier (OCC), has been exploited. The OCC enables to detect deviations from a “Normal Operating Region” (NOR), defined as to include odour concentrations levels unlikely to cause nuisance in the citizenship. Such deviations from the NOR thus should be representative of the odour peaks. The results obtained prove that the IOMS is able to detect real-time alterations of odour emissions from the AT with an accuracy on independent validation data of about 90% (CI95% 55–100%). This ability of detecting anomalous conditions at the AT of the WWTP allowed the targeted withdrawal of liquid and gas samples in correspondence of the odour peaks, then subjected to further analyses that in turn enabled to investigate their origin and take proper counteractions to mitigate the WWTP odour impact.

QPCR-Based Monitoring of 2-Methylisoborneol/Geosmin-Producing Cyanobacteria in Drinking Water Reservoirs in South Korea.

Cyanobacteria can exist in water resources and produce odorants. 2-Methylisoborneol (2-MIB) and geosmin are the main odorant compounds affecting the drinking water quality in reservoirs. In this study, encoding genes 2-MIB (mic, monoterpene cyclase) and geosmin (geo, putative geosmin synthase) were investigated using newly developed primers for quantitative PCR (qPCR). Gene copy numbers were compared to 2-MIB/geosmin concentrations and cyanobacterial cell abundance. Samples were collected between July and October 2020, from four drinking water sites in South Korea. The results showed similar trends in three parameters, although the changes in the 2-MIB/geosmin concentrations followed the changes in the mic/geo copy numbers more closely than the cyanobacterial cell abundances. The number of odorant gene copies decreased from upstream to downstream. Regression analysis revealed a strong positive linear correlation between gene copy number and odorant concentration for mic (R2 = 0.8478) and geo (R2 = 0.601). In the analysis of several environmental parameters, only water temperature was positively correlated with both mic and geo. Our results demonstrated the feasibility of monitoring 2-MIB/geosmin occurrence using qPCR of their respective synthase genes. Odorant-producing, gene-based qPCR monitoring studies may contribute to improving drinking water quality management.

Relationship between human behavior and indoor air quality of private room in a care facility for the elderly in Japan

In Japan, the number of elderly people in need of nursing care is increasing while the population of young people is decreasing, and the potential for labor shortages in the field of elder care is of great concern. This study aimed to estimate the behavior of the elderly by using sensors to monitor indoor air quality (IAQ), without placing undue burden on the elderly or their caregivers. Odor and carbon dioxide (CO2) concentrations were monitored in a private room of a nursing home in the Kanto Region of Japan, the behaviors of the resident and staff members were recorded, and the relationship between the two was analyzed. Both odor and CO2 concentrations were higher when the resident was present than when absent, indicating that the resident was one of the main sources of indoor odor and CO2. In addition, after the resident entered the room, the CO2 concentration increased and remained stable, whereas the odor concentration tended to vary after the resident entered the room, first increasing and later decreasing. This suggested that the increase or decrease in odor could be used to monitor the behavior of the resident and staff members. The relationship between the slopes of odor and CO2 in typical behavioral events suggest that if only odor increases and CO2 does not change, the likelihood of the event in which feces were observed during diaper changes is high. In addition, based on the behavior near the sensor, the rate of CO2 and odor emissions differed between the elderly resident and the younger staff members, suggesting that the ratio of odor slope to CO2 slope may be greater in the elderly than in younger people. Furthermore, the repeated number of increases and decreases in odor and CO2 suggested that multiple events could be distinguished. These results suggest that IAQ can be utilized to estimate the behavior of residents and staff in nursing care facilities for the elderly.

Modeling of olfactory transduction in AWCON neuron via coupled electrical-calcium dynamics.

Amphid wing "C" (AWC) neurons are among the most important and studied neurons of the nematode Caenorhabditis elegans. In this work, we unify the existing electrical and intracellular calcium dynamics descriptions to obtain a biophysically accurate model of olfactory transduction in AWCON neurons. We study the membrane voltage and the intracellular calcium dynamics at different exposure times and odorant concentrations to grasp a complete picture of AWCON functioning. Moreover, we investigate the complex cascade of biochemical processes that allow AWC activation upon odor removal. We analyze the behavior of the different components of the models and, by suppressing them selectively, we extrapolate their contribution to the overall neuron response and study the resilience of the dynamical system. Our results are all in agreement with the available experimental data. Therefore, we provide an accurate mathematical and biophysical model for studying olfactory signal processing in C. elegans.

ODOUR EMISSIONS FROM A MUNICIPAL SOLID WASTE DUMPING AREA THAT ARE AT THE MODERATE STAGE OF DISINTEGRATION

&lt;p&gt;Odour is a major concern as they are termed hazardous to the surroundings as well as life forms when they are exposed to the environment. Odour emission is also one of the indicators of environmental changes that impact the environment. Among the different sources of odour emission, in the dumping yard itself, different types and ages of waste are dumped in the municipal solid waste (MSW) dumping yards. This study aims to relate odour emission and concentration changes caused by different weather patterns. Different periods of waste (fresh waste, moderate waste, and ripened waste) and weather seasons (summer and winter) affect the odour concentrations. Mixtures of gases and intolerable odours are major components of the MSW dumping yard. The odour concentration was monitored in the different periods of waste (moderate wastes) at different locations in the MSW dumping yard. In this study, it was found that meteorological conditions are also one of the main influences on odour concentrations in the environment. In this study, a comprehensive investigation of odour pollution from a local MSW dumping yard has been performed. The odour concentration indicates that the maximum range of aromatic hydrocarbon chemical compounds (volatile organic compounds) reported was T-butylbenzene at 1.41µg/m3 and the minimum range was Sec-butylbenzene at 0.07µg/m3. This study will provide information on odour emissions in urban areas and how VOC (Volatile Organic Compounds) components are present and affect the dumping yards surrounding those areas&lt;/p&gt;&#x0D;

Odour Perception Using a Sniffing Team at a Municipal Solid Waste Treatment Plant: A Case Study

The monitoring of odour intensity, generated by a landfill area, is a difficult activity since it is a multi-source problem with discontinuous odour emissions. A modified sniffing team method is described here and applied to determine the main odour sources in a landfill located in Pomerania, Poland. Four consecutive test sessions were performed during the following months: August, December, April, and June. It was found that the main odour sources are as follows: a closed-chamber composting facility for leach storage; the site wherein technological operations associated with compost turn-over during open-air aeration processes are performed; and the landfill site. The results of the sniffing team method present the indicative values of sensory testing. The application of the presented method was limited by disturbances due to changing atmospheric conditions. The calculated odour intensities and concentrations correspond with real sensitive perceptions of the tested environment.

Continuous odor profile monitoring to study olfactory navigation in small animals.

Olfactory navigation is observed across species and plays a crucial role in locating resources for survival. In the laboratory, understanding the behavioral strategies and neural circuits underlying odor-taxis requires a detailed understanding of the animal's sensory environment. For small model organisms like Caenorhabditis elegans and larval Drosophila melanogaster, controlling and measuring the odor environment experienced by the animal can be challenging, especially for airborne odors, which are subject to subtle effects from airflow, temperature variation, and from the odor's adhesion, adsorption, or reemission. Here, we present a method to control and measure airborne odor concentration in an arena compatible with an agar substrate. Our method allows continuous controlling and monitoring of the odor profile while imaging animal behavior. We construct stationary chemical landscapes in an odor flow chamber through spatially patterned odorized air. The odor concentration is measured with a spatially distributed array of digital gas sensors. Careful placement of the sensors allows the odor concentration across the arena to be continuously inferred in space and monitored through time. We use this approach to measure the odor concentration that each animal experiences as it undergoes chemotaxis behavior and report chemotaxis strategies for C. elegans and D. melanogaster larvae populations as they navigate spatial odor landscapes.

Comparison of Flavor Profile Relationship of Soy Sauce under Different Storage Conditions.

To elucidate the relation of flavor in soy sauce (SS) kept at room temperature (SSAT) and SS kept under accelerated aging condition (SSAA), four analytical instruments, including electronic nose (E-nose), electronic tongue (E-tongue), gas chromatography-mass spectrometry-olfactory combined with solvent assisted flavor evaporation, and amino acid analyzer, were applied for analyzing the overall flavor profiles and flavor constituents in SSAT and SSAA. The results of E-nose and E-tongue showed overall flavor profile in SSAT for 3 weeks was similar to that of SSAA for 1 week, and 6 weeks (SSAT) was similar to 2 weeks (SSAA). In SS, a total of 35 odor-active compounds were identified and quantitated, and 22 compounds with odor activity value ≥1 were determined as key odorants. The compounds with the highest concentration were 4-hydroxy-2,5-dimethyl-3(2H)-furanone (28,756 μg/mL), followed by acetic acid (8838 μg/mL) and maltol (7984 μg/mL). The heatmap and hierarchical cluster analysis indicated that the concentrations of key odorants and amino acids in SSAT for 3 weeks was close to those of SSAA for 1 week, and 6 weeks (SSAT) was similar to 2 weeks (SSAA). Based on the results obtained above, it was concluded that the flavor changes in SSAA for 1 week were equivalent to those in SSAT for 3 weeks.

Gain control in olfactory receptor neurons and the detection of temporal fluctuations in odor concentration.

The ability of the cockroach to locate an odor source in still air suggests that the temporal dynamic of odor concentration in the slowly expanding stationary plume alone is used to infer odor source distance and location. This contradicts with the well-established view that insects use the wind direction as the principle directional cue. This contribution highlights the evidence for, and likely functional relevance of, the capacity of the cockroach's olfactory receptor neurons to detect and process-from one moment to the next-not only a succession of odor concentrations but also the rates at which concentration changes. This presents a challenge for the olfactory system because it must detect and encode the temporal concentration dynamic in a manner that simultaneously allows invariant odor recognition. The challenge is met by a parallel representation of odor identity and concentration changes in a dual pathway that starts from olfactory receptor neurons located in two morphologically distinct types of olfactory sensilla. Parallel processing uses two types of gain control that simultaneously allocate different weight to the instantaneous odor concentration and its rate of change. Robust gain control provides a stable sensitivity for the instantaneous concentration by filtering the information on fluctuations in the rate of change. Variable gain control, in turn, enhances sensitivity for the concentration rate according to variations in the duration of the fluctuation period. This efficiently represents the fluctuation of concentration changes in the environmental context in which such changes occur.