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Nearly monodisperse Co3O4 nanocubes have been prepared by a microwave-assisted solvothermal (MS) method at 180 °C for 20 min. The samples are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD pattern and TEM images of the products illustrated that Co3O4 nanocubes had a cubic phase with a lateral size of ∼20 nm. The gas response of the Co3O4 nanocubes was studied to several typical organic gases. The Co3O4 nanocubes showed good gas sensing performance towards xylene and ethanol vapors with rapid and high responses at a low-operating temperature. The results showed that the Co3O4 nanocubes can be used to fabricate high performance gas sensors.

PurposeThe purpose of this paper is to explore the ability of capillary‐attached gas sensor (CGS) in detecting components of gas mixtures, including a volatile organic gas and hydrogen in a wide range of concentrations.Design/methodology/approachDiverse feature extraction and classification techniques were employed to analyze the response of CGS when applied to different mixtures.FindingsIt was observed that the response of CGS to the above gas mixtures could be distinguishable. While evaluating the results of the classification technique, it was implied that hydrogen, in the presence of the volatile organic gases, could be detected perfectly by analyzing the response of the CGS. Separating techniques, which yielded a high rate of classification, were used to separate mixtures containing hydrogen and organic gases from other organic gas mixtures without hydrogen.Originality/valueThe results presented in this paper prove the ability of CGS in fabricating an olfactory machine for analyzing the components of gas mixtures.

CdO–Fe2O3 precursors are prepared using co-precipitation method in the presence of PEG400. CdO–Fe2O3 nano-powders are obtained through heating the precursors under different conditions. CdO–Fe2O3 thick film sensors are fabricated using CdO–Fe2O3 nano-materials as sensing materials. The XRD analysis results reveal that CdO–Fe2O3 is mainly composed of CdFe2O4 when the precursor is heated at 700 °C for 2 h and the mole ratio of Cd/Fe is 1:2 in the starting materials. The TEM images show that the average particle sizes increase with heating temperature increasing, the particle sizes are in the range of 15–25 nm when heating temperature is 700 °C (2 h). The influence of the heating duration and heating temperature on the gas-sensing properties of the sensors based on CdO–Fe2O3 nano-materials are investigated. The responses to a few kinds of organic gases, such as (CH3)3N and C2H5OH are studied. It is found that the sensor based on CdO–Fe2O3 nano-material (700 °C, 2 h) exhibits high response to dilute trimethylamine when operating at 230 °C. The responses to 1000 ppm and 0.01 ppm (CH3)3N at 230 °C are 1527 and 2, respectively. The response time and recovery time for 1000 ppm trimethylamine are 70 and 170 s.

Methyl-3-pentane was irradiated with 60Co γ rays in the glassy state at 77 K with carbon tetrachloride and pentene-2 as solutes. The yields of the organic gases have been investigated as a function of the solute concentration (0 to 5 mole %). A pentene-2 concentration of 0,8 mole % reduces the yields of the organic gases by 40 % while CCl4 at a concentration of 2,5 mole % reduces these yields by 70 %. The diminution of the yields is explained by a scavenging of the positive charge in the case of pentene-2; carbon tetrachloride exhibits a more complex behaviour; it acts as an electron scavenger by dissociative electron attachment and also probably by absorbing the electronic excitation energy.

Hollow spheres of Fe2TiO5/alpha-Fe2O3 nanocomposite were prepared via a simple impregnating method using carbonaceous polysaccharide microspheres as hard templates. These hollow spheres possessed porous shells contributed by homogeneously arranged alpha-Fe2O3 a and Fe2TiO5 nanocrystals. With the higher specific-surface area provided by the porous spherical shells and lower grain boundary resistant between alpha-Fe2O3 and Fe2TiO5, these hollow spheres showed much improved gas-sensing properties for some organic gases. A sample with a Fe2TiO5/alpha-Fe2O3 ratio of about 1:1 showed the optimum gas-sensing value. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The UV irradiation enhanced ZnO fiber sensors for organic gas detection at room temperature are reported in this paper. It has been well-known that the conductivity of ZnO fibers will increase when they are exposed to UV irradiation. However, it was found in this study that the trend of the conductivity increase under UV irradiation could be reversed if the organic gases adsorbed on the ZnO fiber surface. It was found that a linear relationship exists between the current response and the concentration of the organic gas. The results exhibited simple maneuverability for detecting parts per million concentration of organic gases at room temperature. The possible mechanism of photoconduction sensing for detecting an organic gas under UV light irradiation at room temperature is also discussed.

We fabricated porous gas sensing films composed of TiO2 nanotubes prepared by a hydrothermal treatment for the detection of organic gases, such as alcohol and toluene. The morphology of the sensing films was controlled with a ball-milling treatment and calcination at high temperature to improve the sensitivity of the films. The sensor using nanotubes with the ball-milling treatment exhibited the improved sensor responses to toluene at 500oC. The results obtained indicated the importance of the microstructure control of sensing layers in terms of particle packing density, pore size distribution, and particle size and shape for detecting large sized organic gas molecules.

The analysis and useful gas sensing properties of capillary-attached gas sensor (CGS) have recently been investigated. The aim of the present work was to investigate the possibility of applying CGS as single selective sensor in detecting organic gases. A CGS samples were fabricated and tested by exposure to five different flammable target gases, hydrogen, methanol, ethanol, acetone and 1-butanol. Classic feature extraction and classifiers were employed to analyze the transient response of CGS. Extracted features of fabricated CGS could differentiate between the pure target gases (TG) perfectly. Results indicated this fact that CGS can be applied as a smart single sensor to diagnose TGs.

The atmospheric fluxes of methane (CH4), carbon dioxide (CO2), and reactive organic gases (ROGs) were determined for natural terrestrial petroleum seeps in the Upper Ojai Valley, California, by measuring the emission rates from five vents and scaling these measurements with the known distribution of seeps within the valley. The Upper Ojai Valley seeps emit about 55 m3/day (1942 ft3/day) of gas, of which about 15 m3/day (529 ft3/day; 3.6 Mg/yr) is CH4, about 40 m3/day (1412 ft3/day; 27 Mg/yr) is CO2, and less than 0.05 m3/day (1.765 ft3/day; 0.04 Mg/yr) are ROGs. CH4 and ROG fluxes in the Upper Ojai Valley are, respectively, three and five orders of magnitude less than at the well-characterized Coal Oil Point field, a large offshore seep field located approximately 70 km (43 mi) to the west of the valley. The CO2 flux from these two fields is about the same. The compositions and δ13C values of seep and reservoir gases were also quantified and indicate extensive biodegradation of gaseous hydrocarbons and the input of isotopically enriched CO2 during ascent from the reservoir. Unlike the nearby CH4-dominated marine seeps, the largest percentage of gas emitted by seeps in the Upper Ojai Valley is CO2. Copyright © 2007. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

Continued climate change could have widespread impacts on California’s economy and ecosystems, and on the health of its citizens. Climate change can impact meteorology, emissions, and chemical processing and thereby influence air quality and its associated effects on public health and welfare. Some mobile source emission control technologies in the distant future are likely to be very different than current ones; it is not possible to make quantitative predictions of California’s mobile source emissions inventory for 2050 and 2100. However, investigating the response of the current on-road mobile source inventory to possible future temperatures can provide insights for the near future and suggest actions which are needed to protect California’s air quality. The results of this study indicate that for California surface temperatures predicted by the B1 and A2 IPCC-carbon dioxide (CO2) emissions scenarios, summer-time on-road total (exhaust plus evaporative) reactive organic gases (ROG) emissions from the 2005 motor vehicle fleet will increase by 4 to 5% using temperature projections for mid-century and by 13 to 16% for end-of-century temperature projections. Increases of as much as 30% are seen in evaporative emissions in 2100. California Air Resources Board’s (CARB) mobile source emission factor model (EMFAC) predicts decreases of similar magnitudes for oxides of nitrogen (NOX) emissions. The medium-high emissions scenario results in a positive feedback loop for greenhouse gas (GHG) emissions from on-road motor vehicles, with 4 to 5% increase in methane and 8 to 9% increases in CO2 by 2100. These emissions estimates are strictly a test of the sensitivity of the current California mobile sources emission inventory model to temperature increases, as they do not take into account future growth in mobile source activity, new control regulations, or possible vehicle or fuel technological advances.

In der Troposphare werden infolge des stofflichen Eintrags aus naturlichen und anthropogenen Quellen mannigfaltige photochemische Reaktionen ausgelost. Insbesondere wird die Bildung von Photooxidantien, verursacht durch die Emission reaktiver organischer Gase und Stickoxide als Vorkaufersubstanzen fur Ozon, verandert. Einige grundlegende Reaktionsmechanismen fur den Abbau verschiedener Gruppen organischer Verbindungen werden diskutiert. Der wichtigste Oxidationsmechanismus verlauft uber OH-Reaktionen in einer Radikalkette, die sich vor allem tagsuber in der belasteten Luft bei Sonneneinstrahlung ausbildet. Da uber den Oxidationsmechanismus aromatischer Kohlenwasserstoffe die grosten Wissenslucken bestehen, werden die dafur verantwortlichen bekannten und vorgeschlagenen Reaktionsmechanismen ausfuhrlich erlautert. Schlieslich wird das Problem der steigenden NO2-Konzentrationen in urbaner Luft angesprochen. Emissions of compounds from the Earth's surface, of both natural and anthropogenic origin, initiate a complex series of photochemical reactions in the troposphere. Particular attention is given to the formation of photooxidants caused by the emissions of reactive organic gases and nitrogen oxides, which are precursor substances for ozone. Several fundamental reaction mechanisms are discussed for the degradation of different classes of organic substances. The most important mechanism proceeds by a radical chain involving OH radicals, which is extremely efficient in the polluted troposphere during the daytime. Since the state-of-knowledge on the photooxidation mechanisms for aromatic hydrocarbons is one of the areas of greatest uncertainty in atmospheric chemistry, the degradation pathways for this class of compounds are treated in more detail. Finally, problem of increasing NO2-concentrations in urban air is briefly discussed.

This project addressed the following research need in the Atmospheric System Research (ASR) Science and Program Plan: "Measurements downwind of urban sources of aerosol particles and precursor gases have shown that the mass concentration of secondary organic aerosol (SOA) can be several-fold greater than can be explained on the basis of current model calculations using observed precursor concentrations. ASR will continue conducting laboratory experiments on both gas-phase and aqueous-phase SOA formation to characterize the particle formation and the organic gases that react to form new organic aerosol material on aerosol seeds. ASR will use these experiments to guide the development of comprehensive chemical mechanisms... to guide the development of parameterizations that are simple enough to be applied to aerosol life cycle models."

This work investigated the formation and evolution of organic aerosols (OA) arising from anthropogenic and biogenic sources in a framework that combined state-of-the-science process and regional modeling, and their evaluation against advanced and emerging field measurements. Although OA are the dominant constituents of submicron particles, our understanding of their atmospheric lifecycle is limited, and current models fail to describe the observed amounts and properties of chemically formed secondary organic aerosols (SOA), leaving large uncertainties on the effects of SOA on climate. Our work has provided novel modeling constraints on sources, formation, aging and removal of SOA by investigating in particular (i) the contribution of trash burning emissions to OA levels in a megacity, (ii) the contribution of glyoxal to SOA formation in aqueous particles in California during CARES/CalNex and over the continental U.S., (iii) SOA formation and regional growth over a pine forest in Colorado and its sensitivity to anthropogenic NOx levels during BEACHON, and the sensitivity of SOA to (iv) the sunlight exposure during its atmospheric lifetime, and to (v) changes in solubility and removal of organic vapors in the urban plume (MILAGRO, Mexico City), and over the continental U.S.. We have also developed a parameterization of water solubilitymore » for condensable organic gases produced from major anthropogenic and biogenic precursors based on explicit chemical modeling, and made it available to the wider community. This work used for the first time constraints from the explicit model GECKO-A to improve SOA representation in 3D regional models such as WRF-Chem.« less

Henry’s law constants may usually be used to calculate solubilities of gases at low pressures. If experimental measurements are unavailable values of Henry’s law constants may be estimated by various methods. Several of these methods depend upon quantitative structure-property relationships. A method developed by Hine and Mookerjee depends on the assumption that each bond of a particular type makes approximately the same contribution to the molar free energy change when different organic gases are dissolved in water. The solubility of gases and also the rate at which gases dissolve in cloud droplets is important for the understanding of processes which occur in the atmosphere. A simple model for the uptake of gases by water is based on an analogy with the behaviour of an electric circuit containing resistances in series and in parallel. This model is important for the interpretation of experimental measurements of rates of gas uptake.

One of the most commonly used LED packages on market is the mid-power LED in a lead-frame package, because of its low cost and high lumen efficiency. However, as the lead-frame package consists silver plated copper and white plastic housing, both for increased light reflection; it can gradually become yellowing or darkening when reacting with certain organic gases or chemical compounds when accelerated by high temperature and light radiation. As a result, light decay or lumen reduction can occur in LED lightings. This paper presents an overview on light decay failure modes of commonly used lead-frame LED package. Four types of failure root cause will be discussed: 1) sulfur induced silver darkening; 2) Halogen (Br, Cl) induced silver and silicone encapsulation yellowing; 3) incompatible volatile organic compounds (VOCs) resulted darkening on or around of LED chips; 4) plastic housing material yellowing.

Aerosol liquid water (ALW) influences aerosol radiative properties and the partitioning of gas-phase water-soluble organic compounds (WSOC_g) to the condensed phase. A recent modeling study drew attention to the anthropogenic nature of ALW in the southeastern United States, where predicted ALW is driven by regional sulfate. Herein, we demonstrate that ALW in the Po Valley, Italy, is also anthropogenic but is driven by locally formed nitrate, illustrating regional differences in the aerosol components responsible for ALW. We present field evidence for the influence of controllable ALW on the lifetimes and atmospheric budgets of reactive organic gases and note the role of ALW in the formation of secondary organic aerosol (SOA). Nitrate is expected to increase in importance due to increased emissions of nitrate precursors, as well as policies aimed at reducing sulfur emissions. We argue that the impacts of increased particulate nitrate in future climate and air quality scenarios may be under predicted because they do not account for the increased potential for SOA formation in nitrate-derived ALW, nor do they account for the impacts of this ALW on reactive gas budgets and gas-phase photochemistry.

Se evaluó el impacto de las posibles medidas para reducir las emisiones generadas por fuentes móviles en Costa Rica para ser ejecutadas en el periodo 2010-2015. La estimación de las emisiones se realizó utilizando los factores de emisión obtenidos del modelo Mobile 6 y los datos de actividad distribuidos por tipo de vehículo y combustible. El estudio determinó que la sustitución del 50% de las unidades de transporte público por vehículos más eficientes resulta ser la medida más eficaz para contrarrestar el incremento de las emisiones de NOx y GOT, cercanas al 14,3% y 11,7% anual respectivamente. The impacts of the possible strategies to reduce the emissions from mobile sources in Costa Rica were evaluated for the 2010-2015 period. The total emissions were estimated using emission factors obtained from Mobile 6 model and activity data like fuel and vehicle type distribution. This study found that 50% substitution of public transport vehicles was the most effective measure to lower the anual rate increase for NOx and Total Organic Gases (TOG). Both around 14,3% and 11,7% anually, respectively.

Carbon fiber reinforced plastics (CFRP) show high potential for use in lightweight applications not only in aircraft design, but also in the automotive or wind energy industry. However, processing of CFRP is complex and expensive due to their outstanding mechanical properties. One possibility to manufacture CFRP structures flexibly at acceptable process speeds is high-power laser cutting. Though showing various advantages such as contactless energy transfer, this process is connected to potentially hazardous emission of respirable dust and organic gases. Moreover, the emitted particles may be fibrous, thus requiring particular attention. Here, a systematic analysis of the hazardous substances emitted during laser cutting of CFRP with thermoplastic and thermosetting matrix is presented. The objective is to evaluate emission rates for the total particulate and gaseous fractions as well as for different organic key components. Furthermore, the influence of the laser process conditions shall be assessed, and first proposals to handle the emissions adequately are made.

This paper describes the experiences and insights gained from inventory preparation and emissions processing for the Seasonal Model for Regional Air Quality (SMRAQ) project. The emission inventory was derived from the 1990 and 1995 Ozone Transport Assessment Group (OTAG) inventories. Here we outline the emissions processing strategy used for the May-to-September simulation, summarize the inventory characteristics and corrections made on the OTAG inventories, and describe the quality assurance steps taken as part of the processing. We then provide spatial maps and daily total time series charts of the hourly, gridded emissions of nitrogen oxides (NOx), reactive organic gases (ROG), and carbon monoxide (CO). Large peaks from electric utility point sources and urban mobile sources characterize the NOx emissions, and the NOx emissions in nonpeak regions are primarily mobile-source emissions. ROG emissions are dominated by biogenic isoprene production in the southern United States, and they have a strong seasonal variability. CO emissions are characterized by less variability, with area and mobile sources dominating the inventory. We compare ratios of season-average nonmethane organic gases to NOx between the emission inventory and the Photochemical Assessment Monitoring Stations (PAMS) data, and these comparisons show poor correlation between the inventory and ambient ratios.

The most serious problem in multivariate calibration analysis is that the prediction samples may contain the interferents which are not modeled in the calibration step. Then how to detect the interferents and eliminate their influence is significantly important in order to obtain the correct compositional analysis results. The so-called residual spectra library search is supplied and an iterative loop regression algorithm to successfully correct the spectrum containing two interferents is developed in this paper. Three groups of which each sample contains no, one or two interferents are supplied to amplify the above method. The mean relative standard deviation (RSD) for the three groups are 0.163, 0.375, 0.355%, respectively. There are no comparable difference among these RSDs, which proves the validation of the method provided in this paper. The results specify that PLS with FTIR spectroscopy is a powerful tool to resolve both the multicomponent simultaneous determination and the identification ...

Asphalts are widely used in paving of roads, and water-proof sealing of building roofs, tanks and containers. This study evaluated the qualitative and quantitative characteristics of emissions from hot asphalts and bitumen that included reactive organic gases (ROGs) and particulate matter (PM). The ROGs consisted of several volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs) of environmental concern. The latter included several polynuclear aromatic hydrocarbons (PAHs) and alkanes. An experimental laboratory testing, sampling and analysis protocol was developed for obtaining efficient and cost-effective a priori estimates of asphalt emissions. The investigation identified and quantified the emissions of organics and evaluated the magnitudes as well as particle size distributions of PM emissions. The study demonstrated that the asphalt type and temperature greatly affected the emission characteristics, and that several organic compounds emitted were partitioned between gaseous and...

[1] The dry deposition of volatile organic compounds (VOCs) and its impact on secondary organic aerosols (SOA) are investigated in the Mexico City plume. Gas-phase chemistry and gas-particle partitioning of oxygenated VOCs are modeled with the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) from C3 to C25 alkanes, alkenes, and light aromatics. Results show that dry deposition of oxidized gases is not an efficient sink for SOA, as it removes

In this work, we have implemented a wearable device for detecting the body odor of wearer. The sensing unit of this device consists of four fabric based gas sensors based on nanocomposite between polymers and carboxylic-functionalized single-walled carbon nanotubes (SWNT-COOH) simply fabricated by embroidering on textile. The communication between smelling shirt and computer is based on a serial communication using ZigBee wireless network. We have tested the performance of these sensors with eight types of volatile organic gases. Based on principal component analysis (PCA), it was found that this device is able to track change in the human body odor, thereby showing a potential for application in real-time health status monitoring.

Bad indoor environment is often the reason for health impairment of people who spend most of their time indoors. Modern buildings are almost air tight and air exchange is too low. This problem often occurs in retrofitted buildings. A long time result can be mold formation in buildings. To get early information about bad indoor climate or mold formation, sensor systems which detect volatile organic compounds (VOC) are needed. The biggest challenge in measuring VOC gases in this scenario are the small concentrations. We present a miniaturized preconcentrating gas sensor system with two chambers for measuring organic gases. Preconcentration is realized with a thermoelectric element to activate sampling and desorption process in one chamber, delivering temperature gradients to a highly porous surface. The second chamber consists of a gas detecting element to indicate the preconcentrated VOC. By driving a temperature cycle with longtime cooling and fast heating the gas is preconcentrated and then desorbed quickly. Furthermore an electronic circuit board has been developed to control the complete system. The result is a complete sensor system with mechanical setup, electronic control, measurement, analyzation and peripheral communication. Measurements regarding temperature behavior of the system are performed, as measurements with VOC.

The impacts of home-based telecommuting on travel behavior and personal vehicle emissions for participants in the State of California Telecommuting Pilot Project are analyzed using the most advanced emissions modeling tools currently available. A comparison of participants' telecommuting day travel behavior with their before-telecommuting behavior shows a 27% reduction in the number of personal vehicle trips, a 77% decrease in vehicle-miles traveled (VMT), and 39% (and 4%) decreases in the number of cold (and hot) engine starts. These decreases in travel translate into emissions reductions of: 48% for total organic gases (TOG), 64% for carbon monoxide (CO), 69% for nitrogen oxide (NOx), and 78% for particulate matter (PM). Although the authors developed the methodology to investigate the emissions impacts of telecommuting, the analysis technique can be applied to any demand management or other transportation strategy where all of the necessary model inputs are available. An analysis of the number of personal vehicle trips and VMT partitioned into commute-related and non-commute-related purposes revealed that non-commute personal vehicle trips increased by 0.5 trips per person-day on average, whereas the non-commute VMT decreased by 5.3 miles. This important finding supports (for one indicator, the number of trips) the hypothesis that non-commute travel generation is a potential negative impact of telecommuting. This finding demonstrates the need to monitor these changes as telecommuting moves into the mainstream. In this study, however, the small increase in non-commute trips has a negligible impact compared to the overall travel and emissions savings.

QSPR correlation equations were developed for the prediction of the solubilities of organic gases and vapors in water. A two-parameter correlation with the squared correlation coefficient R2 = 0.977 gives excellent predictions for 95 alkanes, cycloalkanes, alkenes, alkylarenes, and alkynes. A satisfactory description (R2 = 0.941) of the gas solubilities of 406 organic compounds with a large structural variablity was obtained using a five-parameter QSPR equation. Notably, all the parameters involved in these equations can be derived solely from the chemical structure of the compounds which makes them very useful for the prediction of the solubilities of unknown or unavailable compounds.

The chemical mass balance (CMB) receptor model was applied to the nonmethane organic gas (NMOG) database acquired during the San Joaquin Valley Air Quality Study (SJVAQS)/Atmospheric Utility Signatures—Predictions and Experiment (AUSPEX) Regional Model Adaptation Project (SARMAP). During SARMAP, the major contributors to NMOG were vehicle exhaust, liquid gasoline, gasoline vapor, oil production, acetone and unidentified organic compounds. Oil production was the major contributor to NMOG in the southern SJV during the morning hours, ranging from about one-third to one-half of the total NMOG. Contributions of oil production were lower during the afternoon due to increased ventilation, and larger contributions from secondary organic compounds. In the afternoon, the combined fraction of acetone and unidentified or unexplained (difference between calculated and measured mass) NMOG, which is mostly of secondary origin, accounted for about half of the total NMOG at receptor sites. Only the Yosemite and Giant Forest sites showed significant contributions from biogenic emissions. The fact that CMB did not detect significant contributions from biogenic sources in samples collected from sites in the SJV where estimated biogenic emission rates exceed those of either Yosemite or Giant Forest, suggests that biogenic emissions are overestimated in the SARMAP inventory. Source contribution estimates for total motor vehicle emissions averaged 75 and 70% of the total measured NMOG in urban areas during the 0800–1000 and 1200–1400 sampling periods, respectively, compared to the average daily emission inventory contribution of 44%. These results support recent studies which indicate that motor vehicle emissions have been seriously underestimated.

Control strategies for urban ozone traditionally have been based on mass reductions in volatile organic compounds (VOCs). Studies show, however, that some organic gas species (such as alkanes and alcohols) form an order of magnitude less ozone than equal mass emissions of others (such as alkenes and aldehydes). Chemically detailed photochemical models are used to assess uncertainty and variability in reactivity quantification. VOC control strategies based on relative reactivity appear to be robust with respect to nationwide variations in environmental conditions and uncertainties in the atmospheric chemistry. Control of selective organic gas species on the basis of reactivity can offer cost savings over traditional strategies.

In response to increasing regulatory scrutiny related to sources of hazardous air pollutants and reactive organic gases, several recent studies have addressed the characterization and control of volatile organic compound (VOC) emissions from municipal and industrial wastewater treatment plants. VOC emissions from wastewater collection systems have received much less attention. A naturally well-ventilated municipal sewer interceptor that receives significant quantities of VOC-laden industrial wastewater was studied to quantify VOC emissions. Headspace outgassing rates, when summed across four manhole covers, were as high as 2300 m3/h, far exceeding headspace turnover rates previously estimated and published in the technical literature. Individual concentrations of five target VOCs (benzene, toluene, ethylbenzene, total xylenes, and tetrachloroethene) in the sewer headspace ranged from 0 to 46 ppm during three daytime monitoring events and one 24-hour event. Emissions were greatest for toluene, app...

In order to reduce emission of pollutants, regulations such as Clean Air Act in the United States of America or the Integrated Pollution Prevention and Control (IPPC) and the Industrial Emission Directive (IED) in Europe have been voted. On sites like refineries, the end users have implemented systematic control of Volatile Organic Compounds (COV) in the atmosphere, on their equipments (valves, flanges, pump, compressor…). These controls involve methods of detection such as sniffing with a Flame Ionization Detector (FID) managed by an operator according to EPA21 method. This method is time-consuming and exposes operators to hazardous situations when statistical counting shows that the global emission are often connected with few equipments in refineries. Thus, the use of specific IR imaging with a camera as a remote control method sensible to selected organic gases seems a very attractive alternative, even if this method does not able to quantify very accurate leakage rates. This study presented here investigates the influence of several parameters on the detection of COV with IR camera, under controlled laboratory conditions. External parameters such as distance of view, type of gas, wind, and camera configuration parameters are investigated. The measurement enables definition of the limits of the IR imaging method. If the study shows that the camera must be operated by skilled and trained personal to camera tuning and image analyzing, it remains a very interesting alternative method to sniffing in many cases. The next step of the study will involve the use of the camera on various kind of sites using organic gases.

Organic gas is easy to generate from the mold materials of relay parts when relay is used in high ambient temperature, and the contact resistance tends to increase due to the adhesion of this organic gas on the contact, which would be the reason of contact failure. In this paper the electrical life tests with the combination of mold materials have been carried out, the constituents of organic gases which generated from the mold materials and the organic ingredients of adhesion on the contact have been investigated. The research results of organic gas which can affect contact resistance and the discussions of optimum materials have been reported.

The functional relationships of minimum ozone levels to non-methane organic gases (NMOG) and NO x concentrations (and emissions), which are relevant to urban ozone issues, have been investigated using data generated by a single-cell trajectory model as well as outdoor smog chamber data. A general relationship is shown to exist, at least approximately, for outdoor smog chamber simulations with initial precursors and for air masses which have initial input and continuous emissions of precursors and are diluted

An integrated theory is developed to describe the steadystate operation of a suspended-growth bioscrubber for the control of biodegradable, volatile organic gases. The bioscrubber consists of an N-stage absorber and an oxidation reactor. A biomass slurry is circulated between the absorber and the oxidation reactor, t he pollutant is absorbed and partially oxidized in the absorber. Oxidation is completed in the oxidation reactor. Predictions of the theory show that the removal efficiency is a function of Henry's Law constant for the pollutant, the ratio of the liquid flow rate to the gas flow rate, and the number of stages. Since high efficiencies can be achieved for soluble, biodegradable, volatile organic compounds, such systems have the potential to be a low-cost control method.

Spectral interferometry is presented as a tool to monitor the swelling of polymers caused by organic gases or hydrocarbons in waste water as well as the adsorption and interaction of antigens and antibodies in immunoreactions. Modern diode-array technology allows the consequent observation of changes in optical pathlength on a fractional nanometer scale with subsecond repetition times. The theory of multiple-reflection principles in white-light interferometry determines the possibilities and limitations of this method. The optical set-up and some applications in gas sensing and label-free immunosensing are discussed with respect to the sensitivity, selectivity and limits of detection at present.

The Southern California Air Quality Study (SCAQS) provides detailed experimental observations that can be used to explore the causes of the Los Angeles smog problem. In the present study, the CIT photochemical airshed model is updated and then applied to the August 27-29, 1987, SCAQS intensive monitoring period. Using measured meteorological parameters, measured initial and boundary conditions, and the official emission inventory prepared by the government, ozone concentrations are underpredicted by 23% on average. Recent field experiments suggest that emissions of organic gases and carbon monoxide are understated in the official emission inventory. When the organic gas emissions from on-road vehicle engine exhaust are increased as suggested by emission rate measurements made in a Los Angeles area roadway tunnel during SCAQS, ozone predictions match the observed concentrations more closely (the mean normalized bias in ozone predictions for this case is +1%). Reactive hydrocarbon concentrations are underpredicted by 35% in the base case calculation, but are underpredicted by only 12% in the increased emission case. Results of this study thus support prior estimates that the organic gas emissions in Los Angeles have been understated in recent years.

[1] Oceanic emissions of gaseous organic iodine-atom precursors have the potential to significantly affect atmospheric chemistry and climate, however there is currently considerable uncertainty associated with quantifying their sources. We present sea-air fluxes calculated from simultaneous air and seawater measurements of a comprehensive range of volatile organic iodine compounds (VOICs), including CH3I and the less commonly reported dihalomethanes CH2ICl, CH2IBr and CH2I2, made during two cruises in the Atlantic Ocean between 15–58°N. The combined dihalomethane flux provides a global iodine source (∼0.33 ± 0.19 Tg I y−1) comparable to that of CH3I, and a surface iodine atom source 3–4 times higher. However, a 1D atmospheric model reveals that, in the tropical east Atlantic Ocean in the vicinity of Cape Verde, even these combined VOIC fluxes are capable of supporting only ∼10–25% of the observed IO levels, and suggests that a substantial (340–640 nmol I m−2 d−1) additional photochemical source of iodine is required.

Particles suspended in the air can constitute a potential risk for human health and ecosystems (Pope and Dockery, 2006), specially the finest fraction. Although PM10 (particles with a maximum diameter of 10 m) have been included in European directives for a longer time (Directive 1999/30/EC) air quality objectives for finer particles have been just very recently established. For particles with a mean diameter lower than 2.5 m (PM2.5) the UE Directive 2008/50/EC has set a 25 m/m3 threshold for the annual mean concentration. Although the term aerosol includes the particles and the gas in which they are suspended, commonly both terms, particles and aerosols, refer to particles in the atmosphere. A variety of inorganic and organic chemical compounds can be present in the particulate phase. The organic fraction can account for a 20 90 % of the finest fraction, according to some authors, such as (Kanakidou et al., 2005) and, therefore, the knowledge of this fraction is important to prevent human health risks. Both inorganic and organic aerosols can be directly emitted (primary aerosols) or can be formed in the atmosphere as a consequence of multiple physical and chemical processes (secondary aerosols). The presence of secondary organic aerosols (SOA) is specially relevant in urban areas (Zhang et al., 2007). SOA is mainly produced from the oxidation of volatile organic compounds (VOCs), whose products present a sufficiently low volatility to partition into the particle phase according to the gas-particle partitioning theory (Odum et al., 1996) and then nucleate and grow to form organic particles. Presently, SOA is thought to be mainly constituted by polymers, formed through particle phase heterogeneous reactions (Kalberer et al., 2004). Other main components include organic nitrates, such as peroxynitrates and peroxyacylnitrates (Camredon et al., 2007; Kroll and Seinfeld, 2008), and carboxylic acids (Barsanti and Pankow, 2006). In spite of the fact that SOA formation has been the focus of many recent studies, some aspects continue to be not well understood. Simulation chambers represent an ideal vehicle to evaluate SOA formation potential by emitting selected VOCs in the presence of an oxidant under controlled conditions. Many studies in chambers have contributed to increase the knowledge of the oxidation processes of individual organic gases or simple mixes of them. VOCs related to anthropogenic emissions, such as substituted aromatics 12

The effect of air flow rate and prior conditioning of soil on the removal of contaminant organic gases from air by soil bed reactors (SBRs) was experimentally tested in closed systems. Removal rates of methane, ethane and propane were not significantly different from controls indicating that no net removal of these gases occurred during the experiments. Carbon monoxide removal was complete and rapid, while the removal of ethylene appeared to be accelerated with prior exposure of the soil to ethylene (conditioning), suggesting that the induction of microbial populations may be involved. The amount of contaminant gases removed from the air did not significantly change with changes in air flow rate.

Proton-transfer reaction mass spectrometry (PTR-MS) is a technique developed almost exclusively for the detection of gaseous organic compounds in air. Volatile organic compounds (VOCs) in air have both natural and anthropogenic sources. Natural sources include the emission of organic gases by living objects, both plants and animals. A well-known example, which is discussed later in this review, is the emission of a variety of gaseous organic compounds in the breath of animals, which are released from both the digestive system and the lungs. Plants are major sources of organic gases, as is the decay of dead animal and plant matter. Subsequent photochemistry can add further compounds to the mixture. Consequently, even without contributions from humans, ambient air from the Earth’s atmosphere would consist of a complex mixture of VOCs.

Proton-transfer reaction mass spectrometry (PTR-MS) is a technique developed almost exclusively for the detection of gaseous organic compounds in air. Volatile organic compounds (VOCs) in air have both natural and anthropogenic sources. Natural sources include the emission of organic gases by living objects, both plants and animals. A well-known example, which is discussed later in this review, is the emission of a variety of gaseous organic compounds in the breath of animals, which are released from both the digestive system and the lungs. Plants are major sources of organic gases, as is the decay of dead animal and plant matter. Subsequent photochemistry can add further compounds to the mixture. Consequently, even without contributions from humans, ambient air from the Earth’s atmosphere would consist of a complex mixture of VOCs.

We examined the products which resulted from the pyrolysis of halons in a running dieselmotor. Particles were separated by an appropriate filter. The remaining organic gases were bound to modified charcoal and sorbing polymers and analyzed by means of automatic thermo-desorption (ATD). When using a Flame-Ionisation-Detector the gas-chromatograms showed a significant better combustion in case of the halon loaded fluegases compared to the blanks. Likewise one found several new peaks in the chromatograms that result from an Electron-Capture-Detector after halon application.

Using differential electrochemical mass spectrometry, we determined the amount of H2-evolution occuring during formaldehyde oxidation as a function in the potential region of the first oxidation wave. In the second wave, the oxidation product is CO2 in pH 8 solution, as opposed to more alcaline solutions where only formiate is formed. Formaldehyde is reduced to methanol at potentials negative of the RHE.—An electrochemical formaldehyde sensor was built with a sensitivity below 1 ppm. Cross sensitivities towards alcohols can be lowered by UPD of Ag or Hg.

[1] Semi-empirical secondary organic aerosol (SOA) models typically assume a well-mixed organic aerosol phase even in the presence of hydrophobic primary organic aerosols (POA). This assumption significantly enhances the modeled SOA yields as additional organic mass is made available to absorb greater amounts of oxidized secondary organic gases than otherwise. We investigate the applicability of this critical assumption by measuring SOA yields from ozonolysis of a-pinene (a major biogenic SOA precursor) in a smog chamber in the absence and in the presence of dioctyl phthalate (DOP) and lubricating oil seed aerosol. These particles serve as surrogates for urban hydrophobic POA. The results show that these POA did not enhance the SOA yields. If these results are found to apply to other biogenic SOA precursors, then the semiempirical models used in many global models would predict significantly less biogenic SOA mass and display reduced sensitivity to anthropogenic POA emissions than previously thought. Citation: Song, C., R. A. Zaveri, M. L. Alexander, J. A. Thornton, S. Madronich, J. V. Ortega, A. Zelenyuk, X.-Y. Yu, A. Laskin, and D. A. Maughan (2007), Effect of hydrophobic primary organic aerosols on secondary organic aerosol formation from ozonolysis of a-pinene, Geophys. Res. Lett., 34, L20803

[1] We appreciate the opportunity to reply to comments and concerns raised by Tanner and Eatough [2007, hereinafter referred to as TE] on our paper [Novakov et al., 2005]. In the following we address the ‘‘major flaws’’ that they assert. [2] 1. TE state that our work was motivated by a need to reduce OC/EC ratios to match predominantly urban-based emissions inventories. [3] Our objective was to analyze a large number of measured OC/BC values, obtained at different locations and published in a variety of contexts. Our main finding is that ambient OC/BC ratios, taken at face value as published, decrease with BC mass concentrations for all locations. [4] 2. TE claim that we do not consider negative artifact. [5] We concluded that the positive sampling artifact may, at least qualitatively, explain the OC/BC versus BC trend. We provide proof of this explanation using data from SAFARI 2000, which unequivocally show that the OC/BC dependence on BC concentration observed with uncorrected data is removed with positive artifact-corrected values. Regarding the negative artifact, we stated that the data considered are insufficient to evaluate the effect of a negative sampling artifact on OC/BC ratios. [6] 3. TE comment that we used predominantly urban emission data for global estimates of the artifact-induced errors in reported OC/EC ratios. This, they think, implicitly assumes that the correction for gaseous organics adsorbed on the filter is the same for urban as for rural. [7] This inference is incorrect. After saturation of the filter material with organic gases is achieved, the positive artifact diminishes with continued sampling of carbonaceous particles. Thus the magnitude of the positive artifact may tend to be smallest in (urban) areas where carbon particle concentrations are highest, and is certainly not ‘‘clearly dependent of the relative amounts. . .of gaseous organics vis a vis particulate carbon’’ as TE assert. [8] 4. TE state that we have made the extraordinary assumption that OC/EC ratios should remain constant during aerosol transport from urban or source-rich regions to rural and background locations. [9] We make no assumption that OC/BC ratios are constant during aerosol transport from urban to rural areas, nor do we ignore the frequently large contribution of secondary organic aerosols. In the GISS model we account for most secondary OC, which is derived from natural biogenic emissions by assuming it to be proportional to terpene emissions. We report ratios for a variety of locations, both urban and rural, but we do not report data as a function of time after emission. Thus inferences regarding transport or changes of the OC/BC ratio as a function of time since emission cannot be made. [10] We have shown that OC/BC ratios that can be ‘‘substitutes’’ for the artifact-corrected values. We compared these values with OC/BC ratios calculated from published OC and BC emission inventories. This is important because compiled OC and BC emission inventories and, therefore, OC/BC ratios may be significantly uncertain especially for some global regions.