Headspace Air Research Articles

A comparison of linear and exponential regression for estimating diffusive CH4 fluxes by closed-chambers in peatlands

Abstract The closed-chamber method is the most common approach to determine CH4 fluxes in peatlands. The concentration change in the chamber is monitored over time, and the flux is usually calculated by the slope of a linear regression function. Theoretically, the gas exchange cannot be constant over time but has to decrease, when the concentration gradient between chamber headspace and soil air decreases. In this study, we test whether we can detect this non-linearity in the concentration change during the chamber closure with six air samples. We expect generally a low concentration gradient on dry sites (hummocks) and thus the occurrence of exponential concentration changes in the chamber due to a quick equilibrium of gas concentrations between peat and chamber headspace. On wet (flarks) and sedge-covered sites (lawns), we expect a high gradient and near-linear concentration changes in the chamber. To evaluate these model assumptions, we calculate both linear and exponential regressions for a test data set (n = 597) from a Finnish mire. We use the Akaike Information Criterion with small sample second order bias correction to select the best-fitted model. 13.6%, 19.2% and 9.8% of measurements on hummocks, lawns and flarks, respectively, were best fitted with an exponential regression model. A flux estimation derived from the slope of the exponential function at the beginning of the chamber closure can be significantly higher than using the slope of the linear regression function. Non-linear concentration-over-time curves occurred mostly during periods of changing water table. This could be due to either natural processes or chamber artefacts, e.g. initial pressure fluctuations during chamber deployment. To be able to exclude either natural processes or artefacts as cause of non-linearity, further information, e.g. CH4 concentration profile measurements in the peat, would be needed. If this is not available, the range of uncertainty can be substantial. We suggest to use the range between the slopes of the exponential regression at the beginning and at the end of the closure time as an estimate of the overall uncertainty.

Bacterial Kinetics of Sulfur Oxidizing Bacteria and Their Biodeterioration Rates of Concrete Sewer Pipe Samples

The importance of bacteria in catalyzing microbially induced concrete corrosion was evaluated. Experiments were conducted to determine the optimum pH and growth kinetics of four selected bacterial strains (Thiobacillus neapolitanus C2, Thiobacillus thioparus H1, Acidithiobacillus thiooxidans, and Acidiphilium cryptum LHET2). Combinations of these strains were inoculated into flasks containing ∼42 g concrete blocks half-submerged in 600 mL of synthetic wastewater with hydrogen sulfide in the headspace air. Controls not inoculated with bacteria lost 0–3 mg/g concrete over 227 days; in the aqueous phase the minimum pH was 6–6.7 and 19–23 mg of calcium/g concrete was released. Systems inoculated with two species of neutrophilic sulfur oxidizing microorganisms (SOM) lost 8 mg/g concrete; in the aqueous phase the minimum pH was 4.5 and 25 mg of calcium/g concrete was released. The concrete samples incubated with neutrophilic and acidophilic SOM and an acidophilic heterotroph experienced the greatest deterioration, with a total mass loss of 13 mg/g concrete, minimum aqueous pH of 3.0, 28 mg calcium/g concrete released, and 47 mg sulfate/g concrete produced.

Aerating Recycled Water on Mushroom Composting Sites Affects Its Chemical Analysis and the Characteristics of Odor Emissions

Recycled water (RW) containing compost leachate can be a potent source of foul odor on mushroom composting sites. Samples of RW were repeatedly collected from storage tanks and pits of 14 mushroom composting sites in England and Ireland. Relationships between the effects of submerged aeration of the RW, the chemical and microbial characteristics of the RW, and the odors emitted were investigated. Recycled water samples were analyzed for pH, electrical conductivity (EC), redox potential, and dissolved oxygen concentration after 7 to 14 d cold storage. Freeze-dried material from the RW samples was chemically profiled by pyrolysis gas chromatography-mass spectrometry (GC-MS), and the content of odor precursor compounds was determined by the ninhydrin colorimetric method. The headspace air of containerized RW samples was analyzed by thermal desorption GC-MS and with gas detection tubes and assessed for odor intensity (OI) and concentration by panelists and serial dilution olfactometry. The predominant odorants in the headspace and freeze-dried residues of RW samples were volatile sulfur-containing compounds and carboxylic acids. The headspace OI, EC, dry matter content, and redox potential of RW were interrelated. The headspace OI and combined concentration of hydrogen sulfide (H(2)S) + dimethyl sulfide of RW were correlated (R(2) = 0.635; P < 0.001). Prediction of the OI of RW by measuring RW EC and the concentration of headspace sulfides using gas detector tubes enables rapid and low-cost monitoring of RW from mushroom composting sites. Submerged aeration of RW in storage tanks or pits reduced the RW headspace air OI and the combined H(2)S + dimethyl sulfide concentration by 88%.

Maximized PUFA measurements improve insight in changes in fatty acid composition in response to temperature

A general mechanism underlying the response of ectotherms to environmental changes often involves changes in fatty acid composition. Theory predicts that a decrease in temperature causes an increase in unsaturation of fatty acids, with an important role for long-chain poly-unsaturated fatty acids (PUFAs). However, PUFAs are particularly unstable and susceptible to peroxidation, hence subtle differences in fatty acid composition can be challenging to detect. We determined the fatty acid composition in springtail (Collembola) in response to two temperatures (5 degrees C and 25 degrees C). First, we tested different sample preparation methods to maximize PUFAs. Treatments consisted of different solvents for primary lipid extraction, mixing with antioxidant, flushing with inert gas, and using different temperature exposures during saponification. Especially slow saponification at low temperature (90 min at 70 degrees C) in combination with replacement of headspace air with nitrogen during saponification and methylation maximized PUFAs for GC analysis. Applying these methods to measure thermal responses in fatty acid composition, the data showed that the (maximized) proportion of C(20) PUFAs increased at low acclimation temperature. However, C(18) PUFAs increased at high acclimation temperature, which is contrary to expectations. Our study illustrates that PUFA levels in lipids may often be underestimated and this may hamper a correct interpretation of differential responses of fatty acid composition.

A prediction system of oxidation reaction as a solid-state stress condition: Applied to a pyrrole-containing pharmaceutical compound

Stress conditions for predicting oxidative degradation products in solid-state pharmaceutical compounds were investigated. 4-Methyl-2-(3,4-dimethylphenyl)-1-(4-sulfamoylphenyl)pyrrole, Compound A, was used as the model compound for this study and its four main degradation products were due to oxidation, as identified by LC–MS and LC- 1H NMR. In order to develop a prediction system for the oxidation reaction, solid-state Compound A was stored under moisture-saturated conditions. Hydrogen peroxide was added to the solution used to saturate the headspace with moisture and oxygen was substituted for the headspace air, in order to stimulate the oxidation reaction. After optimizing the conditions, a similar degradation product profile to that actually observed in the stability studies was obtained in only 3 days under conditions using 3% hydrogen peroxide at 40 °C. The prediction of the oxidative degradation products in a solid-state pharmaceutical compound was successfully achieved in a short term utilizing this newly developed prediction system.

Influence of ultra‐high pressure sterilization on the structure of polymer films

AbstractThe effect of ultra‐high‐pressure processing on the structure of polymer film pouches, commonly used in food packaging, has been studied. In particular, the effect of an air headspace on the polypropylene heat‐sealing inner layer is reported. With increasing pressure, both nitrogen and oxygen gases become increasingly soluble in the polymer layer. If the pressure is rapidly released, this causes voids and pits to form in the inner layer. An estimate of the increased solubility (70‐fold) is calculated from regular solution theory. Copyright © 2009 John Wiley &amp; Sons, Ltd.

8-2 Fluorotelomer alcohol aerobic soil biodegradation: Pathways, metabolites, and metabolite yields

The biodegradation pathways and metabolite yields of [3- 14C] 8-2 fluorotelomer alcohol [8-2 FTOH, F(CF 2) 7 14CF 2CH 2CH 2OH) in aerobic soils were investigated. Studies were conducted under closed (static) and continuous headspace air flow to assess differences in degradation rate and metabolite concentrations in soil and headspace. Aerobic degradation pathways in soils were in general similar to those in aerobic sludge and bacterial culture. 14C mass balance was achieved in soils incubated for up to 7 months. Up to 35% 14C dosed was irreversibly bound to soils and was only recoverable by soil combustion. The average PFOA yield was approximately 25%. Perfluorohexanoic acid (PFHxA) yield reached approximately 4%. 14CO 2 yield was 6.8% under continuous air flow for 33 days. Three metabolites not previously identified in environmental samples were detected: 3- OH-7-3 acid [F(CF 2) 7CHOHCH 2COOH], 7-2 FT ketone [F(CF 2) 7COCH 3] and 2 H-PFOA [F(CF 2) 6CFHCOOH]. No perfluorononanoic acid (PFNA) was observed. The formation of 2 H-PFOA, PFHxA, and 14CO 2 shows that multiple –CF 2– groups were removed from 8-2 FTOH. 7-3 Acid [F(CF 2) 7CH 2CH 2COOH] reached a yield of 11% at day 7 and did not change thereafter. 7-3 Acid was incubated in aerobic soil and did not degrade to PFOA. 7-2 sFTOH [F(CF 2) 7CH(OH)CH 3], a transient metabolite, was incubated and degraded principally to PFOA. 7-3 Acid may be a unique metabolite from 8-2 FTOH biodegradation. The terminal ratio of PFOA to 7-3 acid ranged between 1.8–2.5 in soils and 0.6–3.2 in activated sludge, sediment, and mixed bacterial culture. This ratio may be useful in evaluating environmental samples to distinguish the potential contribution of 8-2 FTOH biodegradation to PFOA observed versus PFOA originating from other sources.

Nitric oxide gas phase release in human small airway epithelial cells

BackgroundAsthma is a chronic airway inflammatory disease characterized by an imbalance in both Th1 and Th2 cytokines. Exhaled nitric oxide (NO) is elevated in asthma, and is a potentially useful non-invasive marker of airway inflammation. However, the origin and underlying mechanisms of intersubject variability of exhaled NO are not yet fully understood. We have previously described NO gas phase release from normal human bronchial epithelial cells (NHBEs, tracheal origin). However, smaller airways are the major site of morbidity in asthma. We hypothesized that IL-13 or cytomix (IL-1β, TNF-α, and IFN-γ) stimulation of differentiated small airway epithelial cells (SAECs, generation 10–12) and A549 cells (model cell line of alveolar type II cells) in culture would enhance NO gas phase release.MethodsConfluent monolayers of SAECs and A549 cells were cultured in Transwell plates and SAECs were allowed to differentiate into ciliated and mucus producing cells at an air-liquid interface. The cells were then stimulated with IL-13 (10 ng/mL) or cytomix (10 ng/mL for each cytokine). Gas phase NO release in the headspace air over the cells was measured for 48 hours using a chemiluminescence analyzer.ResultsIn contrast to our previous result in NHBE, baseline NO release from SAECs and A549 is negligible. However, NO release is significantly increased by cytomix (0.51 ± 0.18 and 0.29 ± 0.20 pl.s-1.cm-2, respectively) reaching a peak at approximately 10 hours. iNOS protein expression increases in a consistent pattern both temporally and in magnitude. In contrast, IL-13 only modestly increases NO release in SAECs reaching a peak (0.06 ± 0.03 pl.s-1.cm-2) more slowly (30 to 48 hours), and does not alter NO release in A549 cells.ConclusionWe conclude that the airway epithelium is a probable source of NO in the exhaled breath, and intersubject variability may be due, in part, to variability in the type (Th1 vs Th2) and location (large vs small airway) of inflammation.

Multivariate characterisation and quantitative structure–property relationship modelling of nitroaromatic compounds

A multivariate model to characterise nitroaromatics and related compounds based on molecular descriptors was calculated. Descriptors were collected from literature and through empirical, semi-empirical and density functional theory-based calculations. Principal components were used to describe the distribution of the compounds in a multidimensional space. Four components described 76% of the variation in the dataset. PC1 separated the compounds due to molecular weight, PC2 separated the different isomers, PC3 arranged the compounds according to different functional groups such as nitrobenzoic acids, nitrobenzenes, nitrotoluenes and nitroesters and PC4 differentiated the compounds containing chlorine from other compounds. Quantitative structure–property relationship models were calculated using partial least squares (PLS) projection to latent structures to predict gas chromatographic (GC) retention times and the distribution between the water phase and air using solid-phase microextraction (SPME). GC retention time was found to be dependent on the presence of polar amine groups, electronic descriptors including highest occupied molecular orbital, dipole moments and the melting point. The model of GC retention time was good, but the precision was not precise enough for practical use. An important environmental parameter was measured using SPME, the distribution between headspace (air) and the water phase. This parameter was mainly dependent on Henry's law constant, vapour pressure, log P, content of hydroxyl groups and atmospheric OH rate constant. The predictive capacity of the model substantially improved when recalculating a model using these five descriptors only.

Hazardous Off-Gassing of Carbon Monoxide and Oxygen Depletion during Ocean Transportation of Wood Pellets

Five ocean vessels were investigated for the characterization and quantification of gaseous compounds emitted during ocean transportation of wood pellets in closed cargo hatches from Canada to Sweden. The study was initiated after a fatal accident with several injured during discharge in Sweden. The objective with the investigation was to better understand the off-gassing and issues related to workers' exposure. Air sampling was done during transport and immediately before discharge in the undisturbed headspace air above the wood pellets and in the staircase adjacent to each hatch. The samples were analyzed with Fourier transform infrared spectroscopy and direct reading instruments. The following compounds and ranges were detected in samples from the five ships: carbon monoxide (CO) 1460–14650 ppm, carbon dioxide (CO2) 2960–21570 ppm, methane 79.9–956 ppm, butane equivalents 63–842 ppm, ethylene 2–21.2 ppm, propylene 5.3–36 ppm, ethane 0–25 ppm and aldehydes 2.3–35 ppm. The oxygen levels were between 0.8 and 16.9%. The concentrations in the staircases were almost as high as in the cargo hatches, indicating a fairly free passage of air between the two spaces. A potentially dangerous atmosphere was reached within a week from loading. The conclusions are that ocean transportation of wood pellets in confined spaces may produce an oxygen deficient atmosphere and lethal levels of CO which may leak into adjacent access spaces. The dangerous combination of extremely high levels of CO and reduced oxygen produces a fast-acting toxic combination. Measurement of CO in combination with oxygen is essential prior to entry in spaces having air communication with cargo hatches of wood pellets. Forced ventilation of staircases prior to entry is necessary. Redesign, locking and labeling of access doors and the establishment of rigorous entry procedures and training of onboard crew as well as personnel boarding ocean vessels are also important.

Ammonia Emissions Affected by Airflow in a Model Pig House: Effects of Ventilation Rate, Floor Slat Opening, and Headspace Height in a Manure Storage Pit

Laboratory experiments were performed to study the influence of airflow on ammonia emissions from pig house slurry in a model growing/finishing pig house with slurry in the pit and a clean slatted floor with various opening areas, 100%, 33.3%, and 16.7%. The 100% opening area meant that the headspace was an integral part of the room air space, and this configuration was used as the reference treatment. The pig house model had two sidewall inlets and exhaust in the middle of the ceiling. The liquid slurry used was from a growing/finishing pig building and consisted of 1% to 2% dry matter, had pH of 8.05, and TAN (total ammonia nitrogen) of 2.38 g/L. Experiments in a model growing/finishing swine barn were conducted to determine the effects of room ventilation rate, slurry pit air exchange rates, slatted floor openings, and pit headspace on ammonia emissions. The results showed that ammonia emission rate increased as ventilation rate increased with a constant inlet opening. Increase in the slatted floor opening ratio increased the air exchange rate in the slurry pit, resulting in a higher ammonia emission rate. Different correlations between the ammonia emission rate and the air headspace height in the slurry pit caused by the type of flow in the boundary layer influenced the ammonia transport from the slurry surface to the ventilation air. A statistical model was developed to calculate the ammonia emission rate as a function of ventilation rate, slatted floor opening ratio, and slurry pit headspace (R2 = 0.93). It was found that the NH3 emission rate was more sensitive to the ventilation rate than to the slatted floor opening ratio and air headspace height in the pit. In addition, the NH3 emission rate was much more sensitive to variations in the ventilation rate at low ventilation rates than at high ventilation rates. Similar sensitivity responses were obtained for both slatted floor opening ratio and air headspace height.

Qualitative and quantitative characterization of living bacteria by dynamic response parameters of gas sensor array

Dynamic response of an array of metal oxide gas sensors to volatile products of wound infectious agents is experimentally studied. The transients of the response are generated by abrupt exposure of the sensors to the headspace air of the culture with single type of bacteria. The kinetics of each sensor response is described by a limited number of specific parameters used as a set of the sensor outputs. It is experimentally demonstrated that the outputs of the two types, namely the time constants and the weight coefficients, closely correlate with the properties of volatile products of living bacteria and are related to the amount and the type of bacteria by individual proportions. Theoretical aspects of description of the amount and the type of living bacteria by individual sub-sets of the same database of the outputs are analyzed. Principles that allow a gas sensor based system to identify the wound contamination type (qualitative characteristics) and the stage of the infection (quantitative characteristics) by the dynamic response analysis are discussed.

Methane Oxidation in Termite Hindguts: Absence of Evidence and Evidence of Absence

A steep oxygen gradient and the presence of methane render the hindgut internal periphery of termites a potential habitat for aerobic methane-oxidizing bacteria. However, methane emissions of various termites increased, if at all, only slightly when termites were exposed to an anoxic (nitrogen) atmosphere, and (14)CH(4) added to the air headspace over live termites was not converted to (14)CO(2). Evidence for the absence of methane oxidation in living termites was corroborated by the failure to detect pmoA, the marker gene for particulate methane monooxygenase, in hindgut DNA extracts of all termites investigated. This adds robustness to our concept of the degradation network in the termite hindgut and eliminates the gut itself as a potential sink of this important greenhouse gas.

Compositae dermatitis from airborne parthenolide

Compositae dermatitis confined to exposed skin has often been considered on clinical grounds to be airborne. Although anecdotal clinical and plant chemical reports suggest true airborne allergy, no proof has been procured. Feverfew (Tanacetum parthenium) is a European Compositae plant suspected of causing airborne contact allergy, and its most important allergen is the sesquiterpene lactone (SQL) parthenolide (PHL). The aims of this study were to (i) assess the allergenicity of feverfew-derived monoterpenes and sesquiterpenes and their oxidized products in feverfew-allergic patients and (ii) re-assess the role of PHL and other SQLs in airborne contact allergy. Feverfew-allergic patients were patch tested with extracts and fractions containing volatile monoterpenes and sesquiterpenes as well as extracts of airborne particles from flowering feverfew plants, obtained by fractionation of ether extracts, dynamic headspace and high-volume air sampler (HIVAS) technique, respectively. Among 12 feverfew-allergic patients, eight had positive patch-test reactions to a HIVAS filter extract, while two tested positive to a headspace extract. Subsequent analysis of the HIVAS extract by gas chromatography and mass spectrometry detected PHL in a concentration of 510 ng mL(-1) in the HIVAS extract. Testing with a dilution series of PHL showed positive reactions down to 8.1 ng in selected patients. None of the 12 patients tested positive to monoterpenes or sesquiterpenes, whether they were oxidized or not. The clinical results have proved that some feverfew-allergic patients are sensitive to airborne particles released from the plant, and isolation of PHL from the particle-containing HIVAS extract in allergenic amounts is strong evidence of PHL as the responsible allergen.

Low-temperature aeration to control Indianmeal moth, Plodia interpunctella (Hübner), in stored grain in twelve locations in the United States: a simulation study

Aeration management strategies were developed to control cold-acclimated and diapausing Indianmeal moth, Plodia interpunctella (Hübner), larvae in grain bins during winter in north- and east-central regions of the US. The application in this study focuses on corn because it is the dominant crop in these regions, but we believe that the analyses can be applied to other grains as well. Contour maps for hours below −10 °C for the months of December, January, and February were developed to help effective planning and management of aeration to control overwintering stored-grain insects. Two cumulative lethality index (CLI) models were developed to estimate mortality of laboratory-reared (diapausing without cold-acclimation) and field-collected (cold-acclimated, and diapausing with cold-acclimation) P. interpunctella larvae under changing temperature conditions. The CLI models were used for evaluating aeration management strategies. Simulation studies were conducted using 30 years of weather data for 12 locations in north- and east-central regions of the US to evaluate different aeration management strategies for controlling P. interpunctella larvae. For each strategy, temperatures of headspace air and grain in the top meter of the grain mass were simulated using an existing model for the period of December–February. The tested management strategies included no aeration, continuous aeration, and intermittent aeration by controlling fan operation. During aeration, air was pulled from the headspace downward through the grain with an airflow rate of 0.11 m 3/min-t (0.1 cfm/bu). Simulation results indicated that a fan control strategy that turned the aeration fan on when the grain temperature at 0.4-m depth was greater than the headspace-air temperature was the best strategy for managing P. interpunctella larvae in all tested locations. For this strategy, the CLI model indicated that 100% mortality of P. interpunctella larvae could be achieved at a grain depth of 0.4 m from the top grain surface in all locations. For this strategy, the aeration fan operated about 10% of the time from December to February. The average cost of electrical energy required for aeration fan operation with this strategy for all locations was 1.3 ¢/t (0.033 ¢/bu) based on an electrical energy cost of 7 ¢/kWh.

Rapid detection of toxicity in wastewater: Recent developments with manometric respirometry

Manometric respirometry can be used for the direct toxicity assessment (DTA) of wastewater. A first prototype portable system for field use as well as the principle of operation has been reported previously [A. Tzoris, D. Cane, P. Maynard, E.A.H. Hall, Anal. Chim. Acta 460 (2002) 257; A. Tzoris, D. Fearnside, M. Lovell, E.A.H. Hall, Environ. Toxicol. 17 (2002) 284; A. Tzoris, V. Fernandez-Perez, E.A.H. Hall, Sens. Actuators B 105 (2005) 39]. In this report we examine the simple mathematical derivation of the principle and identify some design parameters that could be altered or improved. Hence by changing the geometry of the respiration chamber aiming at a larger surface area and smaller air headspace volume combined with sample stirring for improved aeration, the response of the instrument was improved by at least 50%. Data obtained from real samples as well as data from a comparative study with a lab-based respirometer routinely used in toxicity assessment is presented. Correlation was excellent with the advantage that a test could be completed in 6 min or with five repeat measurements the data could be collected within a 10 min measurement period. Using a 25% inhibition threshold, all samples found toxic by the standard method were also found toxic by the Baroxymeter method and dilution factors could be estimated for pretreatment of the toxic waste prior to release to a processing plant.

Volatile Sulfur Compounds Produced by Helicobacter pylori

To assess the volatile sulfur compounds produced by three strains of Helicobacter pylori in broth cultures mixed with sulfur-containing amino acids. Halitosis has been reported in H. pylori-positive patients, and volatile sulfur compounds such as hydrogen sulfide and methyl mercaptan are known to be responsible for inducing oral malodor. Whether H. pylori produces these volatile sulfur compounds has yet to be established. Three strains of H. pylori (ATCC 43504, SS 1, DSM 4867) were cultured with 5 mM cysteine and methionine. After 72 hours of incubation, the headspace air was aspirated and injected directly into a gas chromatograph. The concentrations of hydrogen sulfide and methyl mercaptan were analyzed and compared between experimental and control cultures In broth containing 5 mM cysteine, hydrogen sulfide was increased by ATCC 43504 (P < 0.01) and SS 1 (P < 0.05), while methyl mercaptan was elevated only by SS 1 (P < 0.05). In broth containing 5 mM methionine, methyl mercaptan increases were significant for SS 1 (P < 0.05) and DSM 4867 (P < 0.05). In broth containing 5 mM cysteine and 5 mM methionine, the concentration of hydrogen sulfide was higher than in controls for all three strains (P < 0.01); that of methyl mercaptan was higher only for SS 1 (P < 0.01). Cysteine addition to cultures containing methionine increased hydrogen sulfide and methyl mercaptan for ATCC 43504 (P < 0.05) and SS 1 (P < 0.05). Conversely, addition of methionine to cultures containing cysteine increased methyl mercaptan only for DSM 4867 (P < 0.01). The production of volatile sulfur compounds by H. pylori is not only very complicated but also strain-specific. Nevertheless, H. pylori was shown to produce hydrogen sulfide and methyl mercaptan, which suggests that this microorganism can contribute to the development of halitosis.

Numerical Simulations of Non-Isothermal Flow in Off-Axis Rotation of a Can Containing a Headspace Bubble

This paper describes numerical simulations of the non-isothermal, laminar flow of Newtonian and non-Newtonian liquids inside rotating cylindrical cans containing a headspace air bubble. Two modes of rotation are considered: axial rotation about a horizontal axis and end-over-end rotation. The rotational speed is held constant so that once initial transients have decayed the flow field in both cases is periodic. The aim of the numerical simulations, carried out using the ANSYS CFX computational fluid dynamics software, is to compare liquid heating times for different flow conditions. To reduce computational run times the calculations are carried out for a liquid with an artificially high value of thermal diffusivity. For axial rotation the simulations have been carried out using 2D and 3D models and it is shown that a 2D model can identify trends in heating times. In both end-over-end and axial modes, rotational speeds and radii of rotation are identified which minimize the heating time. The conditions are shown to correspond closely to those which maximize a measure of mixing in previous studies of isothermal flow.

Discriminant Analysis of Volatile Organic Compounds data related to a new location method of entrapped people in collapsed buildings of an earthquake

Discriminant Analysis is used as a part of a research, which aims at using expired air analysis for the early location of entrapped people under the ruins of collapsed buildings in an earthquake. This work focuses on the possibility of distinguishing Volatile Organic Compounds (VOCs) in the entrapment area which originate from different sources. Five categories of samples were analyzed by Thermal Desorption-Gas Chromatography–Mass Spectrometry (TD-GC–MS). Expired air samples from healthy humans (Category 1) and fasting people (Category 2) were analyzed for studying the VOCs attributed to entrapped people. Headspace air of urban waste disposal bins (Category 3), headspace air of bags with decaying human bodies (Category 4) and urban air samples (Category 5) were analyzed for studying the VOCs attributed to background sources. Discriminant Rotation, a specific type of Discriminant Analysis was applied on the VOCs concentration matrix of the five categories. Combinations of VOCs that best discriminated each category were determined. Cluster Analysis was used to validate the results of Discriminant Analysis. The advantages and limitations of the method are presented and discussed.

Sewer Siphon Assessment and Air Jumper Design

In response to customer complaints about sewer odor, Orange County Sanitation District (OCSD), California launched a project to investigate the ventilation requirements of existing sewer siphons, to verify adequacy of existing air jumper operation, and determine the need for new air jumpers or additional air jumper capacity. The challenge was assessing sewer siphon air jumper adequacy without clear industry standards or guidance for comparison and to then develop air jumper sizing guidelines and recommendations for retrofit replacement or addition of air jumpers at 17 of the existing 87 OCSD sewer siphon locations. A literature search for sewer siphon air jumper sizing guidance was conducted. For each of the 17 sewer siphons studied: siphon inlet and outlet structures were inspected; sewer flow was measured; headspace air pressure or vacuum was measured; air flow into or out of the upstream and downstream siphon structures was measured; and dissolved and headspace hydrogen sulfide levels were measured. Relationships were theorized and developed between: depth of wastewater flow in the sewers; velocity of wastewater flow; sewer headspace airflow rates; and sewer headspace pressure or vacuum with manhole covers in place. General design guidelines for sewer siphon air jumpers were developed and recommended and these guidelines were applied to the field data for each of the studied 17 siphons. Sewer siphon air jumper retrofit replacement or additions are currently in the final design phase with construction scheduled to start in February 2007.