Using Aerosol Light Absorption Measurements for the Quantitative Determination of Wood Burning and Traffic Emission Contributions to Particulate Matter

Abstract

A source apportionment study was performed for particulate matter in the small village of Roveredo, Switzerland, where more than 70% of the households use wood burning for heating purposes. A two-lane trans-Alpine highway passes through the village and contributes to the total aerosol burden in the area. The village is located in a steep Alpine valley characterized by strong and persistent temperature inversions during winter, especially from December to February. During two winter and one early spring campaigns, a seven-wavelength aethalometer, high volume (HIVOL) samplers, an Aerodyne quadrupole aerosol mass spectrometer (AMS), an optical particle counter (OPC), and a Sunset Laboratory OCEC analyzer were deployed to study the contribution of wood burning and traffic aerosols to particulate matter. A linear regression model of the carbonaceous particulate mass in the submicrometer size range CM(PM1) as a function of aerosol light absorption properties measured by the aethalometer is introduced to estimate the particulate mass from wood burning and traffic (PM(wb), PM(traffic)). This model was calibrated with analyses from the 14C method using HIVOL filter measurements. These results indicate that light absorption exponents of 1.1 for traffic and 1.8-1.9 for wood burning calculated from the light absorption at 470 and 950 nanometers should be used to obtain agreement of the two methods regarding the relative wood burning and traffic emission contributions to CM(PM1) and also to black carbon. The resulting PM(wb) and PM(traffic) values explain 86% of the variance of the CM(PM1) and contribute, on average, 88 and 12% to CM(PM1), respectively. The black carbon is estimated to be 51% due to wood burning and 49% due to traffic emissions. The average organic carbon/total carbon (OC/TC) values were estimated to be 0.52 for traffic and 0.88 for wood burning particulate emissions.

Amplification of light absorption of black carbon associated with air pollution

“…The AE33 can measure the 27 absorption coefficient (σab) of sampled aerosols in seven spectral regions (370, 470, 520, 590, 660, 880 and 950 n m). At a 28 wavelength of 880 n m, the absorption of aerosol particles is dominated by BC because the light absorbed by other aerosol 29 components is significantly less (Drinovec et al, 2015;Sandradewi et al, 2008). In this study, the σab at 880 nm measured by 30 the AE33 was used to characterize the light absorption of the BC-containing particles.…”

The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

“…At this wavelength, other aerosol particles (carbonaceous or mineral) absorb significantly less and absorption can be attributed to BC alone (Sandradewi et al, 2008a and b;Fialho et al, 2005;Yang et al, 2009;and references therein). Measurements at distinct spectral regions (370,470,520,590,660,880 and 950 nm) allow for spectral analysis of the data -the analysis of the dependence of absorption on the wavelength can be of importance for research on direct effects of aerosol BC, climate forcing (Bond et al, 2013;IPCC, 2013) or mineral dust detection (Collaud Coen et al, 2004), through the determination of the single scattering albedo dependence on the wavelength, or source apportionment (Sandradewi et al, 2008b). When the attenuation reaches a certain threshold, a tape advance is induced so that measurements start on a clean spot.…”

“…Source apportionment of ambient BC concentrations is based on the Sandradewi et al (2008b) model. Briefly, the twocomponent model considers the aerosol optical absorption coefficient as a sum of biomass burning and fossil fuel combustion fractions and takes advantage of the difference in the wavelength dependence of absorption: since fossil fuel and biomass contributions to aerosol absorption feature specific values of the absorption Ångström exponent, it is possible to construct a source specific two-component model.…”

“…The compensation parameters depend on the wavelength of light used in the analysis (Weingartner et al, 2003). Accurate compensation of absorption measurements is essential if the spectral measurements are used for source apportionment of BC or carbonaceous aerosols (Sandradewi et al, 2008b).…”

Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

“…Several studies have used the absorption spectral dependence to apportion the fossil fuel and BB contributions to total absorption (Favez et al, 2010;Massabò et al, 2015;Sandradewi et al, 2008). However, the å abs values do not always reflect the combustion type and using it as a source apportionment parameter could lead to erroneous results (Garg et al, 2016;Lewis et al, 2008;Wang et al, 2016b).…”