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Title: Loading Effect Correction for Real-time Aethalometer Measurementsof Fresh Diesel Soot

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
COLLABORATION - U.Concepcion/Chile
OSTI Identifier:
925588
Report Number(s):
LBNL-62736
R&D Project: E41301
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the Air and Waste ManagementAssociation; Journal Volume: 57; Related Information: Journal Publication Date: 07/2007
Country of Publication:
United States
Language:
English
Subject:
54

Citation Formats

Jimenez, Jorge, Claiborn, Candis, Larson, Timothy, Gould,Timothy, Kirchstetter, Thomas W., and Gundel, Lara. Loading Effect Correction for Real-time Aethalometer Measurementsof Fresh Diesel Soot. United States: N. p., 2007. Web.
Jimenez, Jorge, Claiborn, Candis, Larson, Timothy, Gould,Timothy, Kirchstetter, Thomas W., & Gundel, Lara. Loading Effect Correction for Real-time Aethalometer Measurementsof Fresh Diesel Soot. United States.
Jimenez, Jorge, Claiborn, Candis, Larson, Timothy, Gould,Timothy, Kirchstetter, Thomas W., and Gundel, Lara. Sun . "Loading Effect Correction for Real-time Aethalometer Measurementsof Fresh Diesel Soot". United States. doi:.
@article{osti_925588,
title = {Loading Effect Correction for Real-time Aethalometer Measurementsof Fresh Diesel Soot},
author = {Jimenez, Jorge and Claiborn, Candis and Larson, Timothy and Gould,Timothy and Kirchstetter, Thomas W. and Gundel, Lara},
abstractNote = {},
doi = {},
journal = {Journal of the Air and Waste ManagementAssociation},
number = ,
volume = 57,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}
  • In this study, a correction was developed for the aethalometer to measure real-time black carbon (BC) concentrations in an environment dominated by fresh diesel soot. The relationship between the actual mass-specific absorption coefficient for BC and the BC-dependent attenuation coefficients was determined from experiments conducted in a diesel exposure chamber that provided constant concentrations of fine particulate matter (PM; PM(2.5); PM < 2.5 microm in aerodynamic diameter) from diesel exhaust. The aethalometer reported BC concentrations decreasing with time from 48.1 to 31.5 microg m(-3) when exposed to constant PM(2.5) concentrations of 55 +/- 1 microg m(-3) and b(scat) = 95more » +/- 3 Mm(-1) from diesel exhaust. This apparent decrease in reported light-absorbing PM concentration was used to derive a correction K(ATN) for loading of strong light-absorbing particles onto or into the aethalometer filter tape, which was a function of attenuation of light at 880 nm by the embedded particles.« less
  • Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IRmore » vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.« less
    Cited by 4
  • Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IRmore » vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA:BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. As a result, this demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.« less
  • In this work, the uncatalysed and catalysed combustion of two commercial carbon blacks and three diesel soot samples were analysed and related to the physico-chemical properties of these carbon materials. Model soot samples are less reactive than real soot samples, which can be attributed, mainly, to a lower proportion in heteroatoms and a higher graphitic order for the case of one of the carbon blacks. Among the diesel soot samples tested, the most relevant differences are the volatile matter/fixed carbon contents, which are directly related to the engine operating conditions (idle or loaded) and to the use of an oxidationmore » catalyst or not in the exhaust. The soot collected after an oxidation catalyst (A-soot) is more reactive than the counterpart virgin soot obtained under the same engine operating modes but before the oxidation catalyst. The reactivity of the different soot samples follows the same trend under uncatalysed and catalysed combustion, the combustion profiles being always shifted towards lower temperatures for the catalysed reactions. The differences between the soot samples become less relevant in the presence of a catalyst. The ceria-zirconia catalysts tested are very effective not only to oxidise soot but also to combust the soluble organic fraction emitted at low temperatures. The most reactive soot (A-soot) exhibits a T{sub 50%} parameter of 450 C when using the most active catalyst. (author)« less
  • The microtransport of polycyclic aromatic hydrocarbons (PAHs) in airborne diesel soot particles over time scales ranging from 0.18 s to 11.9 h was studied via a smog chamber experiment and simulated using radial diffusion models. The sorption of the PAHs by particles over long time periods was studied by monitoring the gas and particle-phase concentrations in the chamber over the course of the experiment. Additionally, the desorption of PAHs from particles over short time scales was observed by passing the aerosol through a large gas-phase stripping device and a sampling denuder to remove the aerosol`s gas phase thus causing themore » PAHs to desorb from the particles. The results of each experimental test were compared to simulation results using a one-layer model and four dual-impedance radial diffusion models. The dual-impedance models were able to closely reproduce the experimental results of each test, while the one-layer model produced poor fits to the experimental data, especially for the rapid desorption tests. The low values of the resulting optimized apparent diffusion coefficients indicate significant impedance to microtransport beyond simple free-liquid diffusion. The mechanisms responsible for these impedances are explored. The results of this study indicate that a dual-impedance radial diffusion model is a useful tool for predicting the microtransport of PAHs in diesel soot particles over a wide range of time scales.« less