Quantification of Absorption Due to Black and Brown Carbon from Biomass Burning and Parameterizations for Comparison to Climate Models Result PDF Download
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Author: Rudra Prasad Pokhrel
Publisher:
ISBN: 9780355446234
Category : Absorption
Languages : en
Pages : 131
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Book Description
This dissertation examines the optical properties of fresh and aged biomass burning aerosols, parameterization of these properties, and development of new instrumentation and calibration techniques to measure aerosol optical properties. Data sets were collected from the fourth Fire Lab at Missoula Experiment (FLAME-4) that took place from October 15 to November 16, 2012. Biomass collected from the various parts of the world were burned under controlled laboratory conditions and fresh emissions from different stages of burning were measured and analyzed. Optical properties of aged aerosol under different conditions was also explored. A photoacoustic absorption spectrometer (PAS) was built and integrated with a newly designed thermal denuder to improve upon observations made during Flame-4. A novel calibration technique for the PAS was developed. Single scattering albedo (SSA) and absorption Angstrom exponent (AAE) from 12 different fuels with 41 individual burns were estimated and parameterized with modified combustion efficiency (MCE) and the ratio of elemental carbon (EC) to organic carbon (OC) mass. The EC / OC ratio has better capability to parameterize SSA and AAE than MCE. The simple linear regression model proposed in this study accurately predicts SSA during the first few hours of plume aging with the ambient data from a biomass burning event. In addition, absorption due to brown carbon (BrC) can significantly lower the SSA at 405 nm resulting in a wavelength dependence of SSA. Furthermore, smoldering dominated burns have larger AAE values while flaming dominated burns have smaller AAE values indicating a large fraction of BrC is emitted during the smoldering stage of the burn. Enhancement in BC absorption (E[superscript]A[superscript]b[superscript]s) due to coating by absorbing and non-absorbing substances is estimated at 405 nm and 660 nm. Relatively smaller values of E[superscript]A[superscript]b[superscript]s at 660 nm compared to 405 nm suggests lensing is a less important contributor to biomass burning aerosol absorption at lower wavelengths. Multiple burns of the same fuel produced significantly different E[superscript]A[superscript]b[superscript]s values at 405 nm, but show good correlation with the EC/OC ratio indicating less dependency on fuel type and more dependency on burn conditions. In addition, absorption due to BrC can contribute up to 92 % of the total biomass burning aerosol absorption at 405 nm and up to 58 % of the total absorption at 532 nm. Indicating BrC absorption in biomass burning emissions is equally or more important than the absorption due to BC at short wavelengths. Furthermore, fractional absorption due to BrC shows reasonably good correlation with EC/OC ratio and AAE.Primary organic aerosol is found to be more volatile than secondary organic aerosol and it is found that the thermal denuder deployed in this study removes less organic aerosol if secondary organic aerosol is present. SSA at 532 nm remains constant during different conditions of aging while SSA at 405 nm increases under certain conditions suggesting the degradation of BrC. Decreases in AAE under the same experiment further support the proposed BrC degradation. The novel thermal denuder designed completely removes non-refractory material and can be used under higher flow rates (maximum of 5 LPM) than the most commercially available thermal denuders. The new calibration techniques proposed for the photoacousitc absorption spectrometer will reduce uncertainty during calibration compared to the conventional calibration methods.
Author: Rudra Prasad Pokhrel
Publisher:
ISBN: 9780355446234
Category : Absorption
Languages : en
Pages : 131
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Book Description
This dissertation examines the optical properties of fresh and aged biomass burning aerosols, parameterization of these properties, and development of new instrumentation and calibration techniques to measure aerosol optical properties. Data sets were collected from the fourth Fire Lab at Missoula Experiment (FLAME-4) that took place from October 15 to November 16, 2012. Biomass collected from the various parts of the world were burned under controlled laboratory conditions and fresh emissions from different stages of burning were measured and analyzed. Optical properties of aged aerosol under different conditions was also explored. A photoacoustic absorption spectrometer (PAS) was built and integrated with a newly designed thermal denuder to improve upon observations made during Flame-4. A novel calibration technique for the PAS was developed. Single scattering albedo (SSA) and absorption Angstrom exponent (AAE) from 12 different fuels with 41 individual burns were estimated and parameterized with modified combustion efficiency (MCE) and the ratio of elemental carbon (EC) to organic carbon (OC) mass. The EC / OC ratio has better capability to parameterize SSA and AAE than MCE. The simple linear regression model proposed in this study accurately predicts SSA during the first few hours of plume aging with the ambient data from a biomass burning event. In addition, absorption due to brown carbon (BrC) can significantly lower the SSA at 405 nm resulting in a wavelength dependence of SSA. Furthermore, smoldering dominated burns have larger AAE values while flaming dominated burns have smaller AAE values indicating a large fraction of BrC is emitted during the smoldering stage of the burn. Enhancement in BC absorption (E[superscript]A[superscript]b[superscript]s) due to coating by absorbing and non-absorbing substances is estimated at 405 nm and 660 nm. Relatively smaller values of E[superscript]A[superscript]b[superscript]s at 660 nm compared to 405 nm suggests lensing is a less important contributor to biomass burning aerosol absorption at lower wavelengths. Multiple burns of the same fuel produced significantly different E[superscript]A[superscript]b[superscript]s values at 405 nm, but show good correlation with the EC/OC ratio indicating less dependency on fuel type and more dependency on burn conditions. In addition, absorption due to BrC can contribute up to 92 % of the total biomass burning aerosol absorption at 405 nm and up to 58 % of the total absorption at 532 nm. Indicating BrC absorption in biomass burning emissions is equally or more important than the absorption due to BC at short wavelengths. Furthermore, fractional absorption due to BrC shows reasonably good correlation with EC/OC ratio and AAE.Primary organic aerosol is found to be more volatile than secondary organic aerosol and it is found that the thermal denuder deployed in this study removes less organic aerosol if secondary organic aerosol is present. SSA at 532 nm remains constant during different conditions of aging while SSA at 405 nm increases under certain conditions suggesting the degradation of BrC. Decreases in AAE under the same experiment further support the proposed BrC degradation. The novel thermal denuder designed completely removes non-refractory material and can be used under higher flow rates (maximum of 5 LPM) than the most commercially available thermal denuders. The new calibration techniques proposed for the photoacousitc absorption spectrometer will reduce uncertainty during calibration compared to the conventional calibration methods.
Author: Hunter Y. Brown
Publisher:
ISBN: 9780355324990
Category : Atmospheric aerosols
Languages : en
Pages : 61
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Book Description
A recent development in the representation of aerosols in climate models is the realization that some components of organic carbon (OC), emitted from biomass and biofuel burning, can have a significant contribution to short-wave radiation absorption in the atmosphere. The absorbing fraction of OC is referred to as brown carbon (BrC). This study introduces one of the first implementations of BrC into the Community Earth System Model (CESM), using a parameterization for BrC absorption described in Saleh et al. (2014). 9-year experiments are run (2003-2011) with prescribed emissions and sea surface temperatures to analyze the effect of BrC in the atmosphere. Model validation is conducted via model comparison to single-scatter albedo (SSA) and aerosol optical depth from the Aerosol Robotic Network (AERONET), as well as comparison with a laboratory derived parameterization for SSA dependent on the (black carbon (BC))/(BC+OC) ratio in biomass burning emissions. These comparisons reveal a model underestimation of SSA in biomass burning regions for both default and BrC model runs. Global annual average radiative effects are calculated due to aerosol-radiation interactions (REari; 0.13±0.021 W m−2), aerosol-cloud interactions (REaci; 0.07±0.056 W m -2), and surface albedo change (REsac; -0.06±0.035 W m−2). REari is similar to other studies’ estimations of BrC direct radiative effect, while REaci indicates a global reduction in low clouds due to the BrC semi-direct effect. REsac suggests increased surface albedo with BrC implementation due to modified snowfall, but does not take into account the warming effect of BrC on snow. Lastly, comparisons of BrC implementation approaches find that this implementation may do a better job of estimating BrC radiative effect in the Arctic regions than previous studies with CESM.
Author: Eric R. Beamesderfer
Publisher:
ISBN: 9781321886702
Category : Atmospheric aerosols
Languages : en
Pages : 85
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Book Description
Emissions from biomass burnings are thought to be responsible for over half of the black carbon aerosol present in the atmosphere. Black carbon, or soot, absorbs significant amounts of solar radiation, and is estimated to be the second most important individual climate-warming agent after CO2 . Organic coatings can significantly increase the absorption of black carbon cores by focusing more light onto the core. Shorter wavelengths of light can also be absorbed by the organic material itself, in which case it is referred to as brown carbon. There remains significant uncertainty concerning the amount of absorption enhancement by organic coatings and the importance of brown carbon in biomass burning emissions. This work presents results from multi-wavelength absorption measurements made during the 2012 FLAME-IV experiment at the Missoula Fire Laboratory that address these uncertainties for a variety of globally important biomass fuels. Absorption was measured with a multi-wavelength (405, 532, 660 nm) Photo-Acoustic Absorption Spectrometer (PAS). Two additional channels at 405 and 660 nm measured particles that had been heated to 250°C and run through a carbon denuder. This study presents observations of absorption enhancement (E [subscript]Abs), which we define to be the ratio of the magnitude of absorption caused by non-altered particles to the magnitude of absorption caused by denuded particles. E[subscript]Abs results presented were compared to the modified combustion efficiency (MCE), absorption angstrom exponent (AAE), and the black carbon to organic aerosol mass ratio for two different experimental setups and a variety of fuels. For the 21 room burn experiments, the average 405 nm E [subscript]Abs was estimated to be 2.19 ± 0.13, while the average 660 nm E[subscript]Abs was 1.18 ± 0.10. Results indicate an EAbs due to lensing at 660 nm for the majority of the burns, with E[subscript]Abs values as high as 1.52 ± 0.20 observed. Brown carbon is a significant source of absorption at 405 nm where E[subscript]Abs values for non-peat fuels range from 1.26 ± 0.02 to 3.87 ± 0.48. Peat burns had the largest 405 nm E[subscript]Abs , as they are clear sources of brown carbon, with little to no absorption recorded on the 405 nm denuded and 660 nm dry and denuded channels. The BC:OA mass for peat was estimated at 0.0028, an order of magnitude lower than any other fuel.
Author: Apoorva Pandey
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 153
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Book Description
Atmospheric aerosols directly affect the Earth's radiative budget by absorbing and scattering solar radiation. Carbonaceous aerosols constitute 20-90% of the global aerosol mass burden and are recognized by the Intergovernmental Panel on Climate Change as important drivers of direct radiative forcing (DRF). Aerosol radiative impacts have been implicated in regional atmospheric warming in South Asia: changing Indian monsoon patterns, and accelerating melting of the Himalayan glaciers. There are systematic global discrepancies between estimates of aerosol absorption optical depths derived from observations and those from climate models. Over South Asia, models predict six times lower aerosol absorption than ground-based observations, leading to a low bias in modeled DRF. To resolve this bias, there is a need to (1) account for relevant emission source types, and associated emission rates, and (2) constrain aerosol optical properties: mass absorption cross-sections (MAC), single scattering albedo (SSA) and scattering directionality parameters (asymmetry parameter or upscatter fraction). To that end, two broad classes of light absorbing carbonaceous aerosols need to be separately dealt with: black carbon (BC) and brown carbon (BrC).BC is known to strongly absorb visible solar radiation and its optical properties have been characterized using both direct measurements and optical models. BC aerosols exhibit aggregate morphologies, with fractal dimensions of 1.8 and 2.6 for fresh and aged particles, respectively. As a simplification, current climate models usually approximate BC aerosols as volume-equivalent spheres and use analytical solutions (known as the Lorenz-Mie theory) of Maxwell's equations for estimating their optical properties. Recent modeling studies employed the numerically-exact superposition transition-matrix method to compute optical cross-sections of fractal aggregates of varying sizes and fractal dimensions. These studies highlight the effect of morphology on BC optical behavior soot but their findings (expressed in terms of fractal properties) cannot be used directly by aerosol experimentalists and climate modelers. Exploiting the theoretical bases of aerosol sizing techniques, I determined empirical relationships between numerically-exact optical properties of fractal BC particles and their equivalent diameters, that can be measured by common aerosol instrumentation. In a related study, I reported improved relationships between scattering directionality parameters of BC aggregates, and compared them with the canonical equations which did not allow for treatment of particle morphology.The second branch of my thesis is concerned with light absorbing organic carbon (OC). OC is conventionally modeled as purely light scattering in radiative transfer calculations. However, this approach has been challenged by mounting observational evidence of a class of OC aerosols exhibiting strong absorption in the near ultra-violet wavelengths and little to no absorption in the near-infrared region. This wavelength dependence of absorption leads to a brownish appearance, hence the name brown carbon. Absorption properties of BrC depend on fuel properties and combustion phase (flaming/smoldering): their observed values are source-specific, spanning an order of magnitude in literature. The focus of this part of my research is on the largest source of OC emissions in South Asia: household biomass cookstoves. I conducted a field study in a household in central India in December 2015 and developed a dataset of emission rates for commonly used biomass fuels from various regions of India, which showed that (1) laboratory cookstove tests underestimated particulate mass emission factors by 2-4 times and (2) cookstove aerosol emissions were dominated by thermally stable OC, which is linked with stronger light absorption than volatile OC.To constrain the MAC values for cookstove OC emissions, I performed optical (transmission and reflection) measurements on filter samples of aerosols collected during the field study. Filter optical measurements are associated with artifacts arising from the interaction of the filter medium with light. Through a laboratory study of a wide variety of combustion aerosols, I developed correction schemes for estimating aerosol-phase light absorption from filter-based measurements. This aided the estimation of absorption characteristics of cookstove particulate emissions and their OC components. We found that light absorbing OC contributes roughly as much as BC to total absorption cross-sections of cookstove emissions at 550 nm wavelength, enhancing their direct forcing efficiency. We proposed values for key absorption characteristics of cookstove OC emissions for use within climate impact assessment and mitigation efforts.
Author: Benjamin Jeffrey Sumlin
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Atmospheric processing of brown carbon (BrC) -- a class of spherical, internally-mixed, light-absorbing organic aerosol -- emitted from smoldering biomass combustion is an understudied phenomenon with implications for climate science, air quality models, and satellite retrieval algorithms. BrC aerosols have received significant attention as a strong contributor to atmospheric light absorption in the shorter visible wavelengths and a driver of UV photochemistry. Their complex refractive indices (m=n+ik), size distributions, and carbon oxidation states dictate their optical properties, atmospheric residence times, and chemical interactions, respectively. There is currently a gap in our understanding of these fundamental particle properties and their evolution with atmospheric processing. Long-range transport and oxidation by O3, OH, and other atmospheric oxidants, as well as exposure to UV light present significant challenges when parameterizing these complex processes.This dissertation is broadly divided into three parts. The first part is a series of laboratory studies and the development of novel mathematical tools to provide a foundational understanding of chemical, physical, and optical properties of BrC aerosol and their evolution upon simulated atmospheric aging. The properties of primary BrC were studied as functions of moisture content, fuel source depth, geographic origin, and fuel packing density. No clear functionality in moisture content, source depth, or geographic origin were observed, however, the fuel packing density was found to have a significant impact on the resulting BrC optical properties. Additionally, the morphology and internal structure of BrC was studied using a centrifugal particle mass analyzer, and the long-standing assumption that BrC is spherical and homogeneous was rigorously verified. This result justifies the application of a new Mie Theory inversion algorithm to obtain the aerosol complex refractive index from laboratory measurements, which serves as an important input parameter in climate models and atmospheric remote sensing. The second part identifies the need for compact, robust, high-sensitivity aerosol instrumentation suitable for laboratory or field studies, and communicates the design, construction, and revision of a new multiwavelength integrated photoacoustic-nephelometer (MIPN). This new instrument is a field-portable instrument that directly measures the aerosol absorption and scattering coefficients at four wavelengths. The final part of this dissertation brings closure to the insights gained in laboratory studies by applying the MIPN to a series of real-world wildfires during FIREX-AQ, a large multiagency field campaign that took place in 2019. Daytime (OH-driven) and nighttime (NO3-driven) oxidation was performed on biomass burning aerosol using a Potential Aerosol Mass reactor aboard the Aerodyne Mobile Laboratory as it sampled wildfire events in Arizona and Oregon. The knowledge gained during these studies will help inform more accurate climate models and satellite remote sensing algorithms to better attribute the effects of atmospherically-processed BrC to global radiative transfer and climate change.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 16
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Book Description
One of the major issues confronting aerosol climate simulations of the Arctic and Antarctic cryospheres is the lack of detailed data on the vertical and spatial distribution of aerosols with which to test these models. This is due, in part, to the inherent difficulty of conducting such measurements in extreme environments. However given the pronounced sensitivity of the polar regions to radiative balance perturbations, it is incumbent upon our community to better understand and quantify these perturbations, and their unique feedbacks, so that robust model predictions of this region can be realized. One class of under-measured radiative forcing agents in the polar region is the absorbing aerosol--black carbon and brown carbon. Black carbon (BC; also referred to as light-absorbing carbon [LAC], refractory black carbon [rBC], and soot) is second only to CO2 as a positive forcing agent. Roughly 60% of BC emissions can be attributed to anthropogenic sources (fossil fuel combustion and open-pit cooking), with the remaining fraction being due to biomass burning. Brown carbon (BrC), a major component of biomass burning, collectively refers to non-BC carbonaceous aerosols that typically possess minimal light absorption at visible wavelengths but exhibit pronounced light absorption in the near-ultraviolet (UV) spectrum. Both species can be sourced locally or be remotely transported to the Arctic region and are expected to perturb the radiative balance. The work conducted in this field campaign addresses one of the more glaring deficiencies currently limiting improved quantification of the impact of BC radiative forcing in the cryosphere: the paucity of data on the vertical and spatial distributions of BC. By expanding the Gulfstream aircraft (G-1) payload for the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility-sponsored ACME-V campaign to include the Single-Particle Soot Photometer (SP2)) and leveraging the ACME-V campaign's deployment within the Arctic Circle during the summer of 2015 (Deadhorse, Alaska [70° 12' 20" N, 148° 30' 42" W]), the truly unique opportunity presented itself to acquire profile data on BC loading at little additional cost. Since the SP2 is a particle-resolved measurement, the resulting data set provides refractory black carbon (rBC) mass loadings, size and mass distributions, and rBC-containing particle mixing state, all of which are expected to readily find value in the modeling community. As part of the ACME-V (http://www.arm.gov/campaigns/aaf2014armacmev) campaign, CO, CO2, and CH4 were also measured, providing the unique opportunity for carbon closure. We will also work closely with modelers who require such data and expect this collaboration will lead directly to a better understanding of the climate impacts of BC in the Arctic. The primary measurement objective was to acquire airborne data on the vertical and spatial distributions of refractory black carbon (rBC) loading, size and mass distribution, and particle mixing state. The primary scientific objective was to provide a targeted data set of rBC particle distributions to better understand and constrain the impact of black carbon radiative forcing in the cryosphere. The SP2-based data set during this campaign is available in the DOE-ARM archive (http://www.arm.gov/campaigns/aaf2015abclp).
Author: Rong Wang
Publisher: Springer
ISBN: 3662464799
Category : Science
Languages : en
Pages : 160
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Book Description
This thesis presents research focusing on the improvement of high-resolution global black carbon (BC) emission inventory and application in assessing the population exposure to ambient BC. A particular focus of the thesis is on the construction of a high-resolution (both spatial and sectorial) fuel consumption database, which is used to develop the emission inventory of black carbon. Above all, the author updates the global emission inventory of black carbon, a resource subsequently used to study the atmospheric transport of black carbon over Asia with the help of a high-resolution nested model. The thesis demonstrates that spatial bias in fuel consumption and BC emissions can be reduced by means of the sub-national disaggregation approach. Using the inventory and nested model, ambient BC concentrations can be better validated against observations. Lastly, it provides a complete uncertainty analysis of global black carbon emissions, and this uncertainty is taken into account in the atmospheric modeling, helping to better understand the role of black carbon in regional and global air pollution.
Author: Jeffrey S. Gaffney
Publisher:
ISBN:
Category : History
Languages : en
Pages : 392
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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: Lynn M. Russell
Publisher:
ISBN:
Category : Air
Languages : en
Pages : 428
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Book Description
Author: András Gelencsér
Publisher: Springer Science & Business Media
ISBN: 1402028873
Category : Science
Languages : en
Pages : 357
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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.
