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Author: Philip Rund Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Improvements in organic aerosol (OA) source apportionment techniques are investigated based on field measurements made in the Southeast US by a Chemical Ionization Mass Spectrometer (CIMS) equipped with a custom Filter Inlet for Gases and AEROsols (FIGAERO), as part of the Southern Oxidant and Aerosol Study (SOAS). Non-Negative Matrix Factorisation (NNMF) is applied to the particulate data in the form of both resolved thermograms and concentration timeseries. Assessments of the variance explained in the input data sets by the NNMF reconstructed approximation are used as a statistical tool for a less subjective choice of the number of factors. Linear correlation coefficients and vector phase angle are also used to produce a quantitative measure of the relative similarity between the output factors both temporally and in regards to composition. Each factor contains specific thermogram behavior (from which volatility information can be derived), unique weights for individual ions corresponding to individual molecular components of measured OA, and diurnal cycles. All three pieces of information were used to assign a specific source to each factor, ultimately showing that the dominant component of OA captured by the FIGAERO-CIMS stems from the oxidation of monoterpenes. Individual molecular components were permitted to belong to multiple and potentially all groupings of OA determined by NNMF, revealing certain factors with similar composition but remarkably different volatility and temporal trends. The median mass contribution determined from each factor produced by this factorisation routine, with no a priori information used as input, align well with those determined by an independent study of particle data during SOAS using a spectral basis set produced from several laboratory chamber experiments. The factorisation routine is shown to be more robust using resolved thermograms as input rather than the concentration timeseries. Of the seven factors given for the thermogram data, three were attributed to monoterpene-derived OA with respective extremely low, low, and semi-volatile behavior. These factors combined represent 68% of the total organic aerosol mass examined. Additionally, two factors were sourced to isoprene chemistry, one correlating with IEPOX-derived SOA, and the other likely relating to photochemistry and exhibiting relatively low volatility. The isporene-related factors accounted for 22% of OA mass. Notably absent in the factorisation of OA is a category exclusively capturing the behavior of particulate organic nitrates (PON). While this may be consistent with relatively low local concentrations of this class of particles, a separate factorisation was performed on only the PON in order to examine the volatility and temporal trends of these potentially important compounds. The added layer of volatility information and molecular level identification of OA composition provided by the FIGAERO-CIMS shows potential with the NNMF algorithm to reproduce atmospherically relevant sources from observations as well as providing framework to further identify chemical processes that lead to these categories based on volatility.
Author: Philip Rund Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Improvements in organic aerosol (OA) source apportionment techniques are investigated based on field measurements made in the Southeast US by a Chemical Ionization Mass Spectrometer (CIMS) equipped with a custom Filter Inlet for Gases and AEROsols (FIGAERO), as part of the Southern Oxidant and Aerosol Study (SOAS). Non-Negative Matrix Factorisation (NNMF) is applied to the particulate data in the form of both resolved thermograms and concentration timeseries. Assessments of the variance explained in the input data sets by the NNMF reconstructed approximation are used as a statistical tool for a less subjective choice of the number of factors. Linear correlation coefficients and vector phase angle are also used to produce a quantitative measure of the relative similarity between the output factors both temporally and in regards to composition. Each factor contains specific thermogram behavior (from which volatility information can be derived), unique weights for individual ions corresponding to individual molecular components of measured OA, and diurnal cycles. All three pieces of information were used to assign a specific source to each factor, ultimately showing that the dominant component of OA captured by the FIGAERO-CIMS stems from the oxidation of monoterpenes. Individual molecular components were permitted to belong to multiple and potentially all groupings of OA determined by NNMF, revealing certain factors with similar composition but remarkably different volatility and temporal trends. The median mass contribution determined from each factor produced by this factorisation routine, with no a priori information used as input, align well with those determined by an independent study of particle data during SOAS using a spectral basis set produced from several laboratory chamber experiments. The factorisation routine is shown to be more robust using resolved thermograms as input rather than the concentration timeseries. Of the seven factors given for the thermogram data, three were attributed to monoterpene-derived OA with respective extremely low, low, and semi-volatile behavior. These factors combined represent 68% of the total organic aerosol mass examined. Additionally, two factors were sourced to isoprene chemistry, one correlating with IEPOX-derived SOA, and the other likely relating to photochemistry and exhibiting relatively low volatility. The isporene-related factors accounted for 22% of OA mass. Notably absent in the factorisation of OA is a category exclusively capturing the behavior of particulate organic nitrates (PON). While this may be consistent with relatively low local concentrations of this class of particles, a separate factorisation was performed on only the PON in order to examine the volatility and temporal trends of these potentially important compounds. The added layer of volatility information and molecular level identification of OA composition provided by the FIGAERO-CIMS shows potential with the NNMF algorithm to reproduce atmospherically relevant sources from observations as well as providing framework to further identify chemical processes that lead to these categories based on volatility.
Author: Caroline Parworth Publisher: ISBN: 9780355594157 Category : Languages : en Pages : 0
Book Description
Aerosols, or particulate matter (PM), can affect climate through scattering and absorption of radiation and influence the radiative properties, precipitation efficiency, thickness, and lifetime of clouds. Aerosols are one of the greatest sources of uncertainty in climate model predictions of radiative forcing. To fully understand the sources of uncertainty contributing to the radiative properties of aerosols, measurements of PM mass, composition, and size distribution are needed globally and seasonally. To add to the current understanding of the seasonal and temporal variations in aerosol composition and chemistry, this study has focused on the quantification, speciation, and characterization of atmospheric PM in urban and rural regions of the United States (US) for short and long periods of time. In the first two chapters, we focus on 1 month of aerosol and gas-phase measurements taken in Fresno, CA, an urban and agricultural area, during the National Aeronautics and Space Administration's (NASA) field study called DISCOVER-AQ. This air quality measurement supersite included a plethora of highly detailed chemical measurements of aerosols and gases, which were made at the same time as similar aircraft column measurements of aerosols and gases. The goal of DISCOVER-AQ is to improve the interpretation of satellite observations to approximate surface conditions relating to air quality, which can be achieved by making concurrent ground- and aircraft-based measurements of aerosols and gases. We begin in chapter 2 by exploring the urban aerosol and gas-phase dataset from the NASA DISCOVER-AQ study in California. Specifically, we discuss the chemical composition and mass concentration of water-soluble PM2.5 that were measured using a particle-into-liquid sampler with ion chromatography (PILS-IC) in Fresno, California from January 13–February 10, 2013. This data was analyzed for ionic inorganic species, organic acids and amines. Gas-phase species including HNO3 and NH3 were collected with annular denuders and analyzed using ion chromatography. Using the thermodynamic E-AIM model, inorganic particle water mass concentration and pH were calculated for the first time in this area. Organic particle water mass concentration was calculated from [kappa]-Köhler theory. In chapter 3 further analysis of the aerosol- and gas-phase data measured during DISCOVER-AQ was performed to determine the effectiveness of a local residential wood burning curtailment program in improving air quality. Using aerosol speciation and concentration measurements from the 2013 winter DISCOVER-AQ study in Fresno, CA, we investigate the impact of residential wood burning restrictions on fine particulate mass concentration and composition. Key species associated with biomass burning in this region include K+, acetonitrile, black carbon, and biomass burning organic aerosol (BBOA), which represents primary organic aerosol associated with residential wood burning. Reductions in acetonitrile associated with wood burning restrictions even at night were not observed and most likely associated with stagnant conditions during curtailment periods that led to the buildup of this long-lived gas. In chapter 4 we transition to the rural aerosol dataset from the DOE SGP site. We discuss the chemical composition and mass concentration of non-refractory submicron aerosols (NR-PM1) that were measured with an aerosol chemical speciation monitor (ACSM) at the DOE SGP site from November 2010 through June 2012. Positive matrix factorization (PMF) was performed on the measured organic aerosol (OA) mass spectral matrix using a newly developed rolling window technique to derive factors associated with distinct sources, evolution processes, and physiochemical properties. The rolling window approach captured the dynamic variations of the chemical properties of the OA factors over time. Three OA factors were obtained including two oxygenated OA (OOA) factors, differing in degrees of oxidation, and a BBOA factor. Sources of NR-PM1 species at the SGP site were determined from back trajectory analyses. NR-PM1 mass concentration was dominated by organics for the majority of the study with the exception of winter, when NH4N33 increased due to transport of precursor species from surrounding urban and agricultural regions and also due to cooler temperatures. Chapter 5 is a continuation of chapter 4, where we will explore the use of the multilinear engine (ME-2) as a factor analysis technique, which is an algorithm used for solving the bilinear model called positive matrix factorization (PMF). The importance of ME-2 and its potential application on the long-term aerosol chemical speciation monitor (ACSM) data collected from the Department of Energy (DOE) Southern Great Plains (SPG) site will be discussed. ME-2 was performed on 19 months of OA mass spectral data obtained from the ACSM at the SGP site. Evaluation of ME-2 results are presented, followed by comparison of ME-2 factor results with corresponding OACOMP factor results reported in chapter 4. We show that ME-2 can determine a biomass burning organic aerosol (BBOA) factor during periods when OACOMP cannot. (Abstract shortened by ProQuest.)
Author: Jeffrey S. Gaffney Publisher: ISBN: Category : History Languages : en Pages : 392
Book Description
Urban aerosols have been identified as important species of concern due to their potential health and environmental impacts. This symposium series book will describe the basic chemistry and physics determining the impacts of aerosol species and will highlight the research results from the measurements that were taken following the collapse of the World Trade Center (WTC) on 9/11/01. The WTC tragedy led to the release of millions of pounds of debris aside from the structural steel, part of which was widely dissipated as aerosols and particulates in the debris cloud over lower Manhattan. Additionally, continuing fires under the debris led to the release of fine combustion related aerosols for a considerable time period in this urban environment. Held during the week of the second anniversary of the WTC tragedy in NYC, the symposium book will describe various aspects of the event, aerosol and gas exposures, and the related impacts of these aerosols. The book contributions will highlight efforts work from atmospheric chemists, meteorologists, health workers, and biologists for a timely compilation of what is known and not known about the composition and transport of tropospheric aerosols in urban environs, particularly those from the WTC collapse. Particular interest is in the acute and chronic environmental effects of these aerosols as they impact human health. Chapters included in the book will also address aerosol lifetimes, aerosol transport and removal processes, acute and chronic health effects to fine aerosol and particulate exposures, and the environmental impacts of aerosols.
Author: András Gelencsér Publisher: Springer Science & Business Media ISBN: 1402028873 Category : Science Languages : en Pages : 357
Book Description
The concept of carbonaceous aerosol has only recently emerged from atmospheric pollution studies; even standard nomenclature and terminology are still unsettled. This monograph is the first to offer comprehensive coverage of the nature and atmospheric role of carbonaceous aerosol particles. Atmospheric chemists, physicists, meteorologists, and modellers will find this a thought-inspiring and sometimes provocative overview of all global phenomena affected by or related to carbonaceous aerosol.
Author: Philip Rund
Author: Philip Rund
Author: Fred Warren McLafferty (Chemiker, USA)
Author: Francesco Canonaco
Author: Kaspar Rudolf Dällenbach
Author: Caroline Parworth
Author: Jeffrey Michael Jaeckels
Author: Philip Joseph Silva
Author: Jeffrey S. Gaffney
Author: András Gelencsér
Author: Rachelle Monique Duvall