Download or read book Processes Govering the Fate and Transport of Volatile Compounds VOCs from the Vadose Zone to Indoor Air written by Inán Liviano Lama and published by . This book was released on 2007 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mass Transport of Volatile Organic Compounds Between the Saturated and Vadose Zones written by Monte S. Harner and published by . This book was released on 1996-12-01 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volatile organic compounds (VOCs) dissolved in the saturated zone are transported into the vadose zone primarily by gaseous phase diffusion. If the saturated zone is remediated, VOCs present in the vadose zone may become a secondary source of contamination for the groundwater The amount of VOCs that remain in the vadose zone is dependent on site hydrology, soil properties, and the chemical properties of the contaminants. The purpose of this study was to determine what conditions caused VOC concentrations in the vadose zone to significantly recontaminate the saturated zone. A one-dimensional numerical model was developed to investigate the transport of a VOC, trichioroethylene, between the saturated and vadose zones under a variety of conditions. The model featured steady-state unsaturated water flow and transient contaminant transport Transport mechanisms included aqueous phase advection-dispersion and gaseous phase diffusion. Partitioning between the water, gas, and soil compartments were modeled as equilibrium processes. Sensitivity analyses were performed on several variables including soil type (homogeneous and heterogeneous profiles), water infiltration rate and vadose zone depth. Results indicated that recontamination was most significant rate, and vadose zone depth. Results indicated that recontamination was most significant in the presence of heterogeneous soils, low infiltration rates and deep vadose zones.

Download or read book Natural Attenuation Assessment of Multiple VOCs in a Deep Vadose Zone written by and published by . This book was released on 2000 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fate of six volatile organic compounds (VOC) in a 150-meter deep vadose zone was examined in support of a RCRA Corrective Measures Study of the Chemical Waste Landfill at Sandia National Laboratories, Albuquerque, New Mexico. The study focused on the modeling of potential future transport of the VOCs to exposure media upon the completion of two separate voluntary corrective measures--soil vapor extraction and landfill excavation--designed to significantly reduce contaminant levels in subsurface soils. modeling was performed with R-UNSAT, a finite-difference simulator that was developed by the U.S. Geological Survey. R-UNSAT facilitated a relatively unique and comprehensive assessment of vapor transport because it (1) simulated the simultaneous movement of all six VOCs, taking into account each constituent's diffusion coefficient as affected by its mole fraction within a mixture of chemicals, and (2) permitted simultaneous assessment of risk to human health via volatilization (air) and drinking water (groundwater) pathways. Modeling results suggested that monitored natural attenuation would represent a viable remedial alternative at the landfill after both voluntary corrective measures were completed.

Download or read book VOC Emissions from Wastewater Treatment Plants written by Prakasam Tata and published by CRC Press. This book was released on 2003-03-26 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: VOC Emissions from Wastewater Treatment Plants: Characterization, Control, and Compliance provides comprehensive information on the subject of Volatile Organic Compound (VOC) emissions from publicly owned treatment works (POTWs). It describes models of emission factors so that readers will know what to expect when models need to be used for the est

Download or read book Measurements of Indoor Toxic VOC Concentrations Attributed to the Residential Storage of Household Products written by and published by . This book was released on 1995 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coupled Processes Diffusive Transport and Biodegradation of Volatile Organic Compounds in Unsaturated Porous Media written by and published by . This book was released on 1998 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diffusive transport of volatile organic compounds (VOCs) and their degradation by bacteria in unsaturated soils are coupled by poorly understood mass transfer kinetics at the gas/water interface. The capability to predict the fate of VOCs in m saturated soil is necessary to evaluate the feasibility of natural attenuation as a VOC remediation strategy. The objective of this study was to develop a mechanistically based mathematical model that considered the interdependence of VOC diffusive transport, mass transfer at the gas/water interface, microbial activity, and sorptive interactions in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOC transport that is induced in engineered remediation processes such as vapor extraction was not considered. The utility of the model was assessed through its ability to describe experimental observations from well-defined experiments in which toluene was used as a representative VOC and diffused through soil columns that contained a toluene degrading bacterium, Pseudomonasputida. The coefficient for gas-liquid mass-transfer, KLa, was found to be a key parameter controlling the ability of bacteria to degrade VOCs. This finding indicates that soil size and geometry are likely to be dominant parameters in assessing the possible success of natural attenuation of VOCs in contaminated unsaturated soils.

Download or read book Significance and Treatment of Volatile Organic Compounds in Water Supplies written by Neil M. Ram and published by CRC Press. This book was released on 1990-02-26 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: Significance and Treatment of Volatile Organic Compounds in Water Supplies reviews EPA-approved analytical methods for VOC analysis, QA/QC, data quality objectives and limits of detection. It covers current methods for the assessment of health effects, including toxicity and carcinogenicity. If you only purchase one book on VOCs-this should be it. Leading authorities present the latest essential information on VOCs in drinking water. This book will be a valuable resource to personnel involved with VOC contamination, treatment, costs, and regulation.

Download or read book Understanding Exposures to Volatile and Semivolatile Organic Compounds in Indoor Environments written by Srinandini Parthasarathy and published by . This book was released on 2016 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: Humans spend most of their time indoors, in residences and commercial buildings. In this thesis, I evaluate exposures to volatile (VOCs) and semivolatile organic compounds (SVOCs) in indoor environments. I use a combination of literature review and evaluation, mechanistic modeling, and skin-wipe collection and analysis to develop an understanding of the role of indoor air as an exposure medium for inhalation and passive dermal uptake of pollutants. This dissertation explores three related research topics on indoor environments and human exposures. In Chapter 2, I conduct a comprehensive review of reported measurements of pollutants found in commercial buildings. I used the literature review to estimate concentration ranges that can be compared to health-based exposure limits as basis for hazard assessment. I use the regulatory exposure limits set by government agencies to calculate hazard indices as the ratio of observed concentrations to regulatory standards. I also compare the odor and pungency thresholds of individual pollutants to observed concentrations to evaluate their potential to exceed odor thresholds. The hazard evaluation identifies the potential for health impacts at concentrations commonly found in commercial buildings. This analysis focuses exclusively on VOCs and SVOCs in commercial buildings and identified a limited set of pollutants that pose health concerns. I also characterize the selected pollutants in terms of the chemical properties that,affect partitioning to various indoor surfaces, and subsequently their fate and transport in indoor environments. Based on chemical properties and indoor fate, I grouped the pollutants into five groups. I use an hierarchical k-means analysis based on octanol-air partitioning coefficient, octanol-water partitioning coefficient, air-water partitioning coefficient, and molecular weight. The pollutants in each group are expected to behave similarly in indoor environments. In Chapter 3, I evaluate the role of buildings operation parameters such as ventilation and filtration in limiting exposures to pollutants originating from indoor and outdoor sources. I use a simple well-mixed-air model of an indoor space to study the impact of ventilation on concentrations of ozone, nitrogen dioxide, carbon monoxide, and radon. I employ a chemical-thermodynamics-(fugacity)-based mass balance model in conjunction with a particle mass balance to study the fate and transport of particulate matter, VOCs, and SVOCs. The fugacity mass balance model accounts for chemical partitioning among air, air-borne particles, and indoor surfaces. I ran the fugacity model with indoor and outdoor source of VOCs and SVOCs and indoor and outdoor sources of particulate matter. I evaluate the consequent inhalation exposures these sources with two outcome metrics, intake fraction (iF) for indoor sources and indoor/outdoor concentration ratio for outdoor sources. The exposure to particulate matter of indoor and outdoor origin was evaluated using the outcome metrics iF and the indoor proportion of outdoor particles (iPOP). The model evaluation shows that ventilation is most effective at controlling exposures to VOCs that have an indoor source. Filtration is seen to be effective at controlling exposures to particulate matter and SVOCs that partition preferentially onto particulate matter. In Chapter 4, I explore the role of indoor air in delivering SVOCs to human occupants through passive dermal uptake. I collected wipe samples from thirteen subjects who were randomly chosen. For each subject, I collected three sequential wipe samples from the forehead and one sample from the palm. I analyzed the samples for a suite of SVOCs and skin lipids (squalene and sapienic acid) in an analytical laboratory using gas chromatography and liquid chromatography. All forehead wipe samples contained SVOCs indicating that air to skin transfer of pollutants for passive dermal uptake could be a significant exposure pathway for SVOCs. Because skin lipid concentrations decrease with depth the quantitation of skin lipid concentrations from each wipe allowed me to estimate the depth of sampling by each skin wipe. This is the first study to quantitatively evaluate the depth of sampling by skin wipes. I use the experimental results together with a theoretical model to explore the potential role of skin as a passive sampler for short-term personal exposures, indoors. For this I develop a metric called the equivalent time of exposure (ETE) to study the usefulness of sequential skin wipe samples as a passive sampler. I used partitioning coefficients from air to skin surface, combined with a dynamic skin mass transport model, to study the theoretical transport of pollutant through the stratum corneum. I compare the modeled concentrations to measured concentrations, at comparable depths. The ETE is the amount of time to which the subject would have to be exposed to a constant air concentration to attain the observed skin-wipe concentration depth profile in the stratum corneum. Based on the ETE, I find that skin wipe samples could be indicative of exposures up to 6 hours prior to wipe sampling, depending on the diffusion coefficient of the pollutant. The overarching goal of this research is to evaluate the role of indoor air in mediating the transfer to human receptors of pollutants released indoors or brought indoors from outdoor sources. The indoor air mass controls the fate and transport of pollutants in indoor spaces, and the rate of delivery of pollutants for inhalation and dermal uptake. The research highlights the important role of air-to-surface and air-to-particle partitioning in facilitating or mitigating source-receptor relationships. The work illustrates future research opportunities for tracking the complex web of indoor/outdoor pathways that bring pollutants into the human environment and into the blood and other viable tissues of the human population.

Download or read book VOCS in Non arid Soils Integrated Demonstration written by United States. Department of Energy and published by . This book was released on 1994 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Control of Volatile Organic Compound Emissions written by Paige Hunter and published by Wiley-Interscience. This book was released on 2000-03-27 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: The complete guide to the control of volatile organic compound (VOC) emissions. With increased regulatory pressures on air pollution emissions, there is a growing need for innovative control technologies in a wide range of industries. This timely and authoritative book explores the science, technology, economics, and applications specific to the control of volatile organic compound (VOC) emissions. Engineer Paige Hunter joins forces with S. Ted Oyama, an expert in VOC control and a renowned ozone chemist, to present a thorough review of both conventional and emerging techniques for the treatment of VOC-containing streams. They provide detailed technical descriptions, up-to-date cost data on processes, and practical information for industry professionals on how to apply the techniques in diverse fields. Coverage includes: * Comparisons of the major conventional control methods for the treatment of VOC-containing streams * The new technologies of membrane filtration, ultraviolet oxidation, and corona destruction * The cutting-edge technology of catalytic ozonation, suitable for retrofitting existing processes or control systems * International aspects of air pollution and VOC control * A comprehensive listing of hazardous air pollutants (HAPSs) and VOCs * Dozens of illustrations and photographs as well as references to Internet resources

Download or read book Thermal Desorption VOC Sampler written by and published by . This book was released on 1998 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Volatile Organic Compounds VOC in the Cloudy Atmosphere written by Miao Wang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volatile Organic Compounds (VOC), including saturated, unsaturated, and other substituted hydrocarbons, play a major role in atmospheric chemistry. They are primarily emitted by anthropogenic and biogenic sources into the atmosphere; they are also transformed in situ by chemical reactions, and more specifically, by photo-oxidation leading to the formation of ozone (O3) and Secondary Organic Aerosol (SOA). By altering the organic fraction of aerosol particles, VOC modify the Earth's radiative balance through a direct effect (absorption and scattering of solar radiation) or through indirect effect by altering cloud microphysical properties. They also present a direct effect on human health and on the environment.During their atmospheric transport, VOC and their oxidation products, Oxygenated Volatile Organic Compounds (OVOC), may partition between the gaseous and aqueous phases depending on their solubility. Clouds have a significant effect on tropospheric chemistry by redistributing trace constituents between phases and by providing liquid water in which aqueous phase chemistry can take place. Indeed, during the cloud lifetime, chemical compounds and particularly VOC are efficiently transformed since clouds favor the development of complex “multiphase chemistry”. The latter presents several particularities. First, photochemical processes inside the droplets are important in the transformation of chemical compounds. Second, aqueous chemical reactions are efficient and can be faster than the equivalent reactions in the gas phase. This can be related to the presence of strong oxidants such as hydrogen peroxide H2O2 or Transition Metal Ions (TMI), which participate in the formation of radicals such as hydroxyl radicals (HO•) that favor oxidation processes. Furthermore, the presence of viable microorganisms has been highlighted and shown to participate in transformations of the chemical species. Finally, these transformations in clouds are also strongly perturbed by microphysical processes that control formation, lifetime and dissipation of clouds. These processes will redistribute the chemical species between the different reservoirs (cloud water, rain, particle phase, gaseous phase, and solid ice phase). In this frame, the transformation of VOC in the cloud medium can lead to the production of secondary compounds contributing to SOA formation, reported as “cloud aqSOA”. This secondary organic aerosol mass produced during the cloud lifetime could explain in part the ubiquity of small dicarboxylic and keto acids and high molecular-weight compounds measured in aerosol particles, fog water, cloud water, or rainwater at many locations, as they have neither substantial direct emission sources nor any identified important source in the gas phase. This aqSOA mass stays in the particle phase after cloud evaporation implying a modification of the (micro)physical and chemical properties of aerosol particles (particle size, chemical composition, morphology). This leads to modifications of their impacts on consecutive cloud or fog cycles (aerosol indirect effects) and of their interactions with incoming radiation by scattering/absorbing (aerosol direct effect). (...).

Download or read book VOC Emissions from Building Products written by Chuck Yu and published by . This book was released on 2002 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Digest describes sources of VOCs in indoor environments, methods to control the amount of emissions from building products and the available VOC guideline values for assessing indoor air quality in buildings. Part 1 of this Digest summarises the VOCs and the range of TVOC emission rates from some typical wall and flooring materials used in buildings. Environmental chamber test methods for measuring VOC emissions from building materials were briefly described. Part 2 describes the air quality guidelines and the emission databases used for assessing the impact of VOC emissions in the indoor environment; also labelling schemes for controlling VOC emissions from building materials.

Download or read book Volatile Organic Compounds VOCs In Indoor Air written by Todd A. Wetzel and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Indoor air concentrations of volatile organic compounds (VOCs), including many with documented adverse health effects, vary widely but are generally higher than found outdoors. Volatile organic compounds can enter indoor environments via internal (e.g. paints, paint strippers, fuels, cleaning supplies, pesticides, building materials, adhesives) and external sources (e.g. vapor intrusion (VI) from contaminated soil and/or groundwater and ambient air from automobiles and industrial facilities). Since many consumer products contain volatile organic compounds (VOCs) that are also the focus of soil and groundwater cleanup projects, emissions of these VOCs can lead to false source identifications during VI investigations. Laboratory-measured emissions of VOCs from several consumer products were used with a standard box model to predict indoor air concentrations. The predicted concentrations were compared to measured values generated by introducing the same consumer products into an actual residence. The screening level agreement between measured and estimated air concentrations suggests that a standard box model can be used with laboratory measured emission rates to show if an emission source can cause a potential health risk or lead to false assumption during VI investigations. The use of plant leaves as a simple, cost-effective and sustainable approach to sampling indoor air concentrations of VOCs was also investigated in three studies: 1) a headspace approach; 2) a flow-through glass and stainless steel plant growth chamber, and 3) a house-scale study where plant leaf and air concentrations of VOC were simultaneously measured. Similar relationships between the leaf and air concentrations observed in the three studies suggest that plant leaf concentrations can be used as a surrogate for indoor air concentrations of VOCs.

Download or read book Volatile Organic Compounds written by Peder Wolkoff and published by . This book was released on 1996 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Volatile Organic Compounds in the Atmosphere written by R M Harrison and published by Royal Society of Chemistry. This book was released on 2007-10-31 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interest in volatile organic compounds (VOCs) as air pollutants has increased dramatically in recent years. This book covers a number of very topical issues concerning VOCs, including stratospheric ozone depletion due to CFCs, and the properties of alternative substances; the role of VOCs in the photochemical formation of lower atmosphere (tropospheric) ozone; and the problem of the direct toxicity of VOCs such as benzene and formaldehyde. This Issue reviews our current knowledge of VOCs, drawing upon the expertise of renowned experts and major national and international research programmes. It examines man-made and natural sources, as well as pathways and chemical reactions in the atmosphere. It also looks closely at the sources and concentrations of VOCs indoors, where humans are most likely to be exposed to them. Volatile Organic Compounds in the Atmosphere describes techniques used for the calculation of emissions inventories and strategies for control, and explores the many Government policy matters relating to VOCs. It provides readers with in-depth, clearly explained coverage of the many complex scientific and policy issues surrounding VOCs in the atmosphere.

Download or read book Volatile Organic Compounds written by and published by . This book was released on 2016-09-01 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: