scholarly journals Single particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium

2015 ◽  
Vol 15 (22) ◽  
pp. 32157-32183 ◽  
Author(s):  
A. K. Y. Lee ◽  
M. D. Willis ◽  
R. M. Healy ◽  
J. M. Wang ◽  
C.-H. Jeong ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Black Carbon ◽  
High Molecular Weight ◽  
Biomass Burning ◽  
Single Particle ◽  
Critical Role ◽  
Organic Aerosol ◽  
Mixing State ◽  
Particle Measurements ◽  
Near Ultraviolet

Abstract. Biomass burning is a major source of black carbon (BC) and primary organic aerosol globally. In particular, biomass burning organic aerosol (BBOA) is strongly associated with atmospheric brown carbon (BrC) that absorbs near ultraviolet and visible light, resulting in significant impacts on regional visibility degradation and radiative forcing. The mixing state of BBOA can play a critical role in the prediction of aerosol optical properties. In this work, single particle measurements from a soot-particle aerosol mass spectrometer coupled with a light scattering module (LS-SP-AMS) were performed to examine the mixing state of BBOA, refractory black carbon (rBC) and potassium (K+, a tracer for biomass burning aerosol) in an air mass influenced by aged biomass burning. Cluster analysis of single particle measurements identified five BBOA-related particle types. rBC accounted for 3–14 w.t. % of these particle types on average. Only one particle type exhibited a strong ion signal for K+, with mass spectra characterized by low molecular weight organic species. The remaining four particle types were classified based on the apparent molecular weight of the BBOA constituents. Two particle types were associated with low potassium content and significant amounts of high molecular weight (HMW) organic compounds. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and illustrate that HMW BBOA can be a key contributor to low-volatility BrC observed in BBOA particles.

scholarly journals Single-particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium

2016 ◽  
Vol 16 (9) ◽  
pp. 5561-5572 ◽  
Author(s):  
Alex K. Y. Lee ◽  
Megan D. Willis ◽  
Robert M. Healy ◽  
Jon M. Wang ◽  
Cheol-Heon Jeong ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Biomass Burning ◽  
Single Particle ◽  
Radiative Forcing ◽  
Critical Role ◽  
Organic Aerosol ◽  
Mixing State ◽  
Particle Measurements ◽  
Near Ultraviolet

Abstract. Biomass burning organic aerosol (BBOA) can be emitted from natural forest fires and human activities such as agricultural burning and domestic energy generation. BBOA is strongly associated with atmospheric brown carbon (BrC) that absorbs near-ultraviolet and visible light, resulting in significant impacts on regional visibility degradation and radiative forcing. The mixing state of BBOA can play a critical role in the prediction of aerosol optical properties. In this work, single-particle measurements from a Soot-Particle Aerosol Mass Spectrometer coupled with a light scattering module (LS-SP-AMS) were performed to examine the mixing state of BBOA, refractory black carbon (rBC), and potassium (K, a tracer for biomass burning aerosol) in an air mass influenced by wildfire emissions transported from northern Québec to Toronto, representing aged biomass burning plumes. Cluster analysis of single-particle measurements identified five BBOA-related particle types. rBC accounted for 3–14 wt % of these particle types on average. Only one particle type exhibited a strong ion signal for K+, with mass spectra characterized by low molecular weight organic species. The remaining four particle types were classified based on the apparent molecular weight of the BBOA constituents. Two particle types were associated with low potassium content and significant amounts of high molecular weight (HMW) organic compounds. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and illustrate that HMW BBOA can be a key contributor to low-volatility BrC observed in BBOA particles. The average mass absorption efficiency of low-volatility BBOA is about 0.8–1.1 m2 g−1 based on a theoretical closure calculation. Our estimates indicate that low-volatility BBOA contributes ∼ 33–44 % of thermo-processed particle absorption at 405 nm; and almost all of the BBOA absorption was associated with low-volatility organics.

scholarly journals Single particle diversity and mixing state measurements

2014 ◽  
Vol 14 (12) ◽  
pp. 6289-6299 ◽  
Author(s):  
R. M. Healy ◽  
N. Riemer ◽  
J. C. Wenger ◽  
M. Murphy ◽  
M. West ◽  
...  
Keyword(s):  
Species Diversity ◽  
Ammonium Nitrate ◽  
Black Carbon ◽  
Mass Spectrometer ◽  
Single Particle ◽  
Organic Aerosol ◽  
Particle Mass ◽  
Mixing State ◽  
Mass Fractions ◽  
State Index

Abstract. A newly developed framework for quantifying aerosol particle diversity and mixing state based on information-theoretic entropy is applied for the first time to single particle mass spectrometry field data. Single particle mass fraction estimates for black carbon, organic aerosol, ammonium, nitrate and sulfate, derived using single particle mass spectrometer, aerosol mass spectrometer and multi-angle absorption photometer measurements are used to calculate single particle species diversity (Di). The average single particle species diversity (Dα) is then related to the species diversity of the bulk population (Dγ) to derive a mixing state index value (χ) at hourly resolution. The mixing state index is a single parameter representation of how internally/externally mixed a particle population is at a given time. The index describes a continuum, with values of 0 and 100% representing fully external and internal mixing, respectively. This framework was applied to data collected as part of the MEGAPOLI winter campaign in Paris, France, 2010. Di values are low (~ 2) for fresh traffic and wood-burning particles that contain high mass fractions of black carbon and organic aerosol but low mass fractions of inorganic ions. Conversely, Di values are higher (~ 4) for aged carbonaceous particles containing similar mass fractions of black carbon, organic aerosol, ammonium, nitrate and sulfate. Aerosol in Paris is estimated to be 59% internally mixed in the size range 150–1067 nm, and mixing state is dependent both upon time of day and air mass origin. Daytime primary emissions associated with vehicular traffic and wood-burning result in low χ values, while enhanced condensation of ammonium nitrate on existing particles at night leads to higher χ values. Advection of particles from continental Europe containing ammonium, nitrate and sulfate leads to increases in Dα, Dγ and χ. The mixing state index represents a useful metric by which to compare and contrast ambient particle mixing state at other locations globally.

scholarly journals Single particle diversity and mixing state measurements

2014 ◽  
Vol 14 (3) ◽  
pp. 3973-4005 ◽  
Author(s):  
R. M. Healy ◽  
N. Riemer ◽  
J. C. Wenger ◽  
M. Murphy ◽  
M. West ◽  
...  
Keyword(s):  
Species Diversity ◽  
Ammonium Nitrate ◽  
Black Carbon ◽  
Mass Spectrometer ◽  
Single Particle ◽  
Organic Aerosol ◽  
Particle Mass ◽  
Mixing State ◽  
Mass Fractions ◽  
State Index

Abstract. A newly developed framework for quantifying aerosol particle diversity and mixing state based on information-theoretic entropy is applied for the first time to single particle mass spectrometry field data. Single particle mass fraction estimates for black carbon, organic aerosol, ammonium, nitrate and sulphate, derived using single particle mass spectrometer, aerosol mass spectrometer and multi-angle absorption photometer measurements are used to calculate single particle species diversity (Di). The average single particle species diversity (Dα) is then related to the species diversity of the bulk population (Dγ) to derive a mixing state index value (χ) at hourly resolution. The mixing state index is a single parameter representation of how internally/externally mixed a particle population is at a given time. The index describes a continuum, with values of 0% and 100% representing fully external and internal mixing, respectively. This framework was applied to data collected as part of the MEGAPOLI winter campaign in Paris, France 2010. Di values are low (∼2) for fresh traffic and woodburning particles that contain high mass fractions of black carbon and organic aerosol but low mass fractions of inorganic ions. Conversely, Di values are higher (∼4) for aged carbonaceous particles containing similar mass fractions of black carbon, organic aerosol, ammonium, nitrate and sulphate. Aerosol in Paris is estimated to be 59% internally mixed in the size range 150–1067 nm, and mixing state is dependent both upon time of day and air mass origin. Daytime primary emissions associated with vehicular traffic and woodburning result in low χ values, while enhanced condensation of ammonium nitrate on existing particles at night leads to higher χ values. Advection of particles from continental Europe containing ammonium, nitrate and sulphate leads to increases in Dα, Dγ and χ. The mixing state index represents a useful metric by which to compare and contrast ambient particle mixing state at other locations globally.

Derivation of the material models for ultra-high molecular-weight polyethylene fiber-reinforced armor-grade composites with different architectures

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Mica Grujicic ◽  
Jennifer Snipes ◽  
S. Ramaswami ◽  
Vasudeva Avuthu ◽  
Chian-Fong Yen ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Design Methodology ◽  
Critical Role ◽  
Fiber Reinforcement ◽  
Mechanical Tests ◽  
Transverse Impact ◽  
Material Models ◽  
Polyethylene Fiber ◽  
Ultra High Molecular Weight

Purpose To overcome the problem of inferior through-the-thickness mechanical properties displayed by armor-grade composites based on 2-D reinforcement architectures, armor-grade composites based on 3D fiber-reinforcement architectures have recently been investigated experimentally. Design/methodology/approach The subject of the present work is armor-grade composite materials reinforced using ultra-high-molecular-weight polyethylene fibers and having four (two 2D and two 3D) prototypical architectures, as well as the derivation of the corresponding material models. The effect of the reinforcement architecture is accounted for by constructing the appropriate unit cells (within which the constituent materials and their morphologies are represented explicitly) and subjecting them to a series of virtual mechanical tests. The results obtained are used within a post-processing analysis to derive and parameterize the corresponding homogenized-material models. One of these models (specifically, the one for 0°/90° cross-collimated fiber architecture) was directly validated by comparing its predictions with the experimental counterparts. The other models are validated by examining their physical soundness and details of their predictions. Lastly, the models are integrated as user-material subroutines, and linked with a commercial finite-element package, in order to carry out a transient non-linear dynamics analysis of ballistic transverse impact of armor-grade composite-material panels with different reinforcement architectures. Findings It is found that the reinforcement architecture plays a critical role in the overall ballistic limit of the armor panel, as well as in its structural and damage/failure response. Originality/value To the authors’ knowledge, the present work is the first reported attempt to assess, computationally, the utility and effectiveness of 3D fiber-reinforcement architectures for ballistic impact applications.

scholarly journals The single-particle mixing state and cloud scavenging of black carbon at a high-altitude mountain site in southern China

2017 ◽  
Author(s):  
Guohua Zhang ◽  
Qinhao Lin ◽  
Long Peng ◽  
Xinhui Bi ◽  
Duohong Chen ◽  
...  
Keyword(s):  
Black Carbon ◽  
Single Particle ◽  
Southern China ◽  
Climate Impacts ◽  
Limited Information ◽  
Mixing State ◽  
Cloud Droplets ◽  
Mountain Site ◽  
Cloud Scavenging ◽  
Scavenging Efficiency

Abstract. In the present study, a ground-based counterflow virtual impactor (GCVI) was used to sample cloud droplet residual (cloud RES) particles, while a parallel PM2.5 inlet was used to sample cloud-free or cloud interstitial (cloud INT) particles. The mixing state of black carbon (BC)-containing particles in a size range of 0.1–1.6 µm and the mass concentrations of BC in the cloud-free, RES and INT particles were investigated using a single particle aerosol mass spectrometer (SPAMS) and two aethalometers, respectively, at a mountain site (1690 m a.s.l.) in southern China. The measured BC-containing particles were internally mixed extensively with sulfate, and were activated into cloud droplets to the same extent as all the measured particles. The results indicate the preferential activation of larger particles and/or that the production of secondary compositions shifts the BC-containing particles towards larger sizes. BC-containing particles with an abundance of both sulfate and organics were activated less than those with sulfate but limited organics, implying the importance of the mixing state on the incorporation of BC-containing particles into cloud droplets. The mass scavenging efficiency of BC with an average of 33 % was similar for different cloud events independent of the air mass. This is the first time that both the mixing state and cloud scavenging of BC in China have been reported. Since limited information on BC-containing particles in the free troposphere is available, the results also provide an important reference for the representation of BC concentrations, properties, and climate impacts in modeling studies.

High-Molecular-Weight, High-Unsaturation Copolymers of Isobutylene and Conjugated Dienes. I. Synthesis

1976 ◽  
Vol 49 (4) ◽  
pp. 960-966 ◽  
Author(s):  
W. A. Thaler ◽  
D. J. Buckley
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cationic Polymerization ◽  
Critical Role ◽  
Conjugated Dienes ◽  
Solution Properties ◽  
Insight Into

Abstract This investigation has provided insight into the critical role of solution properties on the course of cationic polymerization and has led to a technique for reconciling the opposing demands for synthesis of isoolefin-diene copolymers both free from gel and high in molecular weight. By this technique, the synthesis of a broad range of intermediate-unsaturation elastomers of quality has been realized.

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