American Association for Aerosol Research - Abstract Submission

AAAR 36th Annual Conference
October 16 - October 20, 2017
Raleigh Convention Center
Raleigh, North Carolina, USA

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A Systematic Inter-Comparison of Black Carbon Measurement Techniques using Biomass Burning Smoke

HANYANG LI, Kara D. Lamb, Joshua P. Schwarz, Vanessa Selimovic, Robert J. Yokelson, Gavin McMeeking, Andrew May, The Ohio State University

     Abstract Number: 458
     Working Group: Carbonaceous Aerosols in the Atmosphere

Abstract
Black carbon (BC) plays a major role in the climate system due to its ability to absorb solar radiation. One major source of BC is open biomass burning, which contributes roughly 40% of global BC emissions. These emissions are estimated from BC emission factors (EFBC; e.g., g-BC per kg-dry-fuel-burned). However, uncertainties in these EFBC is quite large and propagate through the total BC emissions estimates to atmospheric model predictions.

One challenge in reducing the uncertainty in EFBC is the many different techniques that are used for BC measurement. These techniques can be broadly categorized as light absorption, laser-induced incandescence, or thermal-optical analysis; the BC mass quantified by each type is inherently different. These differences must be reconciled in order to reduce uncertainties in reported EFBC values. Because emission inventories are typically based on real-world measurements, which are limited in number, the value of our dataset is heightened.

To address this issue, we conducted a systematic inter-comparison of eight different instruments at the Fire Sciences Laboratory in Missoula, MT during Autumn 2016 as part of the Fire Influence on Regional and Global Environments Experiment (FIREX) campaign. In this effort, we sampled fires from North American biomass burning fuels, in which aerosol emissions were stored in a 55-gallon drum to allow simultaneous sampling of identical aerosol via different instruments. In our presentation, we will focus only on our real-time measurements of BC concentrations from a Droplet Measurement Techniques (DMT) Photoacoustic Extinctiometer, a DMT Single Particle Soot Photometer, and several filter-based light-absorption instruments.

We have derived EFBC for each instrument and observed that the ratios between techniques are often different from one, yet the correlations are generally good, considering the number of covariates (e.g., modified combustion efficiency, single scattering albedo, angstrom absorption exponent). Nevertheless, we are continuing to explore the role of these covariates on differences between instruments in order to provide a robust set of recommendations that can be used to constrain uncertainties between different measurement techniques and improve emission inventory EFBC values.