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Author: Alan J.. Kwan
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 370
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Book Description
Secondary organic aerosol (SOA) are important components in atmospheric processes and significantly impact human health. The complexity of SOA composition and formation processes has hampered efforts to fully characterize their impacts, and to predict how those impacts will be affected by changes in climate and human activity. Here, we explore SOA formation in the laboratory by coupling an environmental chamber with a suite of analytical tools, including a gas-phase mass spectrometry technique that is well suited for tracking the hydrocarbon oxidation processes that drive SOA formation. Focusing on the oxidation of isoprene by the nitrate radical, NO3, we find that reactions of peroxy radicals (RO2) to form ROOR dimers is an important process in SOA formation. The other gas-phase products of these RO2 reactions differ from what is expected from studies of simpler radicals, indicating that more studies are necessary to fully constrain RO2 chemistry. Finally, we examine the role of heterogeneous oxidation as a sink of organic aerosol and a source of oxygenated volatile organic compounds in the free troposphere.
Author: Alan J.. Kwan
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 370
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Book Description
Secondary organic aerosol (SOA) are important components in atmospheric processes and significantly impact human health. The complexity of SOA composition and formation processes has hampered efforts to fully characterize their impacts, and to predict how those impacts will be affected by changes in climate and human activity. Here, we explore SOA formation in the laboratory by coupling an environmental chamber with a suite of analytical tools, including a gas-phase mass spectrometry technique that is well suited for tracking the hydrocarbon oxidation processes that drive SOA formation. Focusing on the oxidation of isoprene by the nitrate radical, NO3, we find that reactions of peroxy radicals (RO2) to form ROOR dimers is an important process in SOA formation. The other gas-phase products of these RO2 reactions differ from what is expected from studies of simpler radicals, indicating that more studies are necessary to fully constrain RO2 chemistry. Finally, we examine the role of heterogeneous oxidation as a sink of organic aerosol and a source of oxygenated volatile organic compounds in the free troposphere.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
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 solubility 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.
Author: Arsineh N. Hecobian
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages :
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Book Description
An existing method for the measurement of atmospheric gaseous species was modified to collect data on aerosol concentrations. Data from biomass burning events in different regions (Canada, the Arctic and California) were collected during April to July, 2008 and the concentrations and evolution of secondary organic aerosols were discussed. And finally, data on the light absorbing properties of water soluble organic aerosols were collected in Atlanta, GA and compared with filter data for the same properties. The results presented in this thesis showed that a negative ion chemical ionization mass spectrometer (CIMS), can be modified by the addition of a thermally denuded inlet to measure aerosol phase sulfuric acid. This system can also be used to measure other aerosol phase organic acids. In the biomass burning plumes studied in the second part, no clear indication of formation of secondary aerosol or gaseous species was observed, except for peroxyacetyl nitrate (PAN). Filter data collected from FRM sites in the Southeastern U.S. showed that biomass burning is the most dominant source of water soluble light absorbing carbonaceous aerosol in this region. The data from a study in Atlanta, GA showed that the online PILS-LWCC-WSOC system might be used for measurements of light absorbing properties of aerosols and WSOC.
Author: Yue Zhang
Publisher: American Chemical Society
ISBN: 0841299293
Category : Science
Languages : en
Pages : 176
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Book Description
The uncertainties in the aerosol effects on radiative forcing limit our knowledge of climate change, presenting us with an important research challenge. Aerosols in Atmospheric Chemistry introduces basic concepts about the characterization, formation, and impacts of ambient aerosol particles as an introduction to graduate students new to the field. Each chapter also provides an up-to-date synopsis of the latest knowledge of aerosol particles in atmospheric chemistry.
Author: Amy Patricia Sullivan
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages :
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Book Description
This thesis characterizes the ambient fine organic carbon aerosol and investigates its sources through the development and deployment of new measurement techniques. The focus is on organic compounds that are soluble in water (WSOC), which comprise a large fraction of the organic aerosol, yet little has been known about its chemical nature. A method was developed for quantitative on-line measurements of WSOC by using a Particle-into-Liquid Sampler (PILS) to capture ambient particles into a flow of purified water, which is then forced through a liquid filter and the carbonaceous content quantified by a Total Organic Carbon (TOC) analyzer. This system allows for a continuous 6 minute (ground-based) or 3 s integrated measurement (airborne) with a limit of detection of 0.1 microgramsC/m3 and uncertainty of 10%. Furthermore, a new quantitative method was developed to group speciate the WSOC. In the first step, WSOC is separated by use of XAD-8 resin into its hydrophilic (WSOCxp) and hydrophobic (WSOCxr) fractions. This separation can be performed on-line by coupling the XAD-8 column with the PILS-TOC or off-line on WSOC extracted from integrated filter samples. If off-line, a second step involving size-exclusion chromatography (SEC) is used to chromatographically separate by organic functional groups the WSOCxp and recovered hydrophobic fraction (WSOCxrr). During this step, the WSOCxp is further separated into aliphatic acids with less than four carbons, neutrals, and bases. The WSOCxrr can be separated into acids and neutrals. Results showing the capabilities of the PILS-TOC both on the ground at the St. Louis Midwest Supersite and when airborne during the New England Air Quality Study/Intercontinental Transport and Chemical Transformation 2004 mission conducted in the northeastern U.S. will be presented. Ambient results from urban sites where a PILS-TOC was coupled with a XAD-8 column will be discussed. Data from the two-step speciation performed on samples collected from urban Atlanta summer and winter, and biomass burning in rural Georgia in a region of prescribed burning are presented. Finally, WSOC measurements obtained in Atlanta and its surrounding regions from both the speciation measurements and PILS-TOC will be used to investigate the sources of WSOC in the southeastern U.S.
Author: Guenter Engling
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 128
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Book Description
Author: Guoshun Zhuang
Publisher: Springer
ISBN: 9789811029806
Category : Science
Languages : en
Pages :
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Book Description
This book systematically investigates the characteristics, distribution, transformation, source and sink of aerosols over typical regions in China based on long-term observations, revealing that the secondary aerosol, dust, and biomass burning are the main causes of widespread smog. It proposes that organic aerosol, sulfate, nitrate and black carbon are the main extinction components in smog. In addition it quantitatively determines the influence of transport on local and regional air quality, and argues that traffic emissions are the triggering factor for the wide range of smog in China. It also demonstrates the mixing and interaction mechanism of dust with anthropogenic pollutants in long-distance transport and the air-sea exchange. The research findings and the large number of first-hand data provided make this a valuable reference resource for those involved in atmospheric science, especially basic atmospheric chemistry and aerosol science research.
Author: Mark E. Erupe
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages :
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Book Description
The research in this dissertation explored the sources and chemistry of organic nitrogen aerosols in the atmosphere. Two approaches were employed: field measurements and laboratory experiments. In order to characterize atmospheric aerosol, two ambient studies were conducted in Cache Valley in Northern Utah during strong winter inversions of 2004 and 2005. The economy of this region is heavily dependent on agriculture. There is also a fast growing urban population. Urban and agricultural emissions, aided by the valley geography and meteorology, led to high concentrations of fine particles that often exceeded the national ambient air quality standards. Aerosol composition was dominated by ammonium nitrate and organic species. Mass spectra from an aerosol mass spectrometer revealed that the organic ion peaks were consistent with reduced organic nitrogen compounds, typically associated with animal husbandry practices. Although no direct source characterization studies have been undertaken in Cache Valley with an aerosol mass spectrometer, spectra from a study at a swine facility in Ames, Iowa, did not show any evidence of reduced organic nitrogen species. This, combined with temporal and diurnal characteristics of organic aerosol peaks, was a pointer that the organic nitrogen species in Cache Valley likely formed from secondary chemistry. Application of multivariate statistical analyses to the organic aerosol spectra further supported this hypothesis. To quantify organic nitrogen signals observed in ambient studies as well as understand formation chemistry, three categories of laboratory experiments were performed. These were calibration experiments, smog chamber studies, and an analytical method development (ion chromatographic method).
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309175917
Category : Science
Languages : en
Pages : 179
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Book Description
This book recommends the initiation of an "integrated" research program to study the role of aerosols in the predicted global climate change. Current understanding suggest that, even now, aerosols, primarily from anthropogenic sources, may be reducing the rate of warming caused by greenhouse gas emissions. In addition to specific research recommendations, this book forcefully argues for two kinds of research program integration: integration of the individual laboratory, field, and theoretical research activities and an integrated management structure that involves all of the concerned federal agencies.
Author: Xiaolu Zhang
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages :
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Book Description
900 archived FRM filters from 15 sites over the southeast during 2007 were analyzed for PM2.5 chemical composition and physical properties. Secondary components (i.e. sulfate aerosol and SOA) were the major contributors to the PM2.5 mass over the southeast, whereas the contribution from biomass burning varied with season and was negligible (2%) during summer. Excluding biomass burning influence, FRM WSOC was spatially homogeneous throughout the region, similar to sulfate, yet WSOC was moderately enhanced in locations of greater predicted isoprene emissions in summer. On smaller spatial scale, a substantial urban/rural gradient of WSOC was found through comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008, indicating important contribution from anthropogenic emissions. A comparative study between Atlanta and LA reveals a number of contrasting features between two cities. WSOC gas-particle partitioning, investigated through the fraction of total WSOC in the particle phase, Fp, exhibited differing relationships with ambient RH and organic aerosols. In Atlanta, both particle water and organic aerosol (OA) can serve as an absorbing phase. In contrast, in LA the aerosol water was not an important absorbing phase, instead, Fp was correlated with OA mass. Fresh LA WSOC had a consistent brown color and a bulk absorption per soluble carbon mass at 365 nm that was 4 to 6 times higher than freshly-formed Atlanta soluble organic carbon. Interpreting soluble brown carbon as a property of freshly-formed anthropogenic SOA, the difference in absorption per carbon mass between the two cities suggests most WSOC formed within Atlanta is not from an anthropogenic process similar to LA.
