 |
| Titel |
Evaluation of the carbon content of aerosols from the burning of biomass in the Brazilian Amazon using thermal, optical and thermal-optical analysis methods |
| VerfasserIn |
L. L. Soto-García, M. O. Andreae, T. W. Andreae, P. Artaxo, W. Maenhaut, T. Kirchstetter, T. Novakov, J. C. Chow, O. L. Mayol-Bracero |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 9 ; Nr. 11, no. 9 (2011-05-12), S.4425-4444 |
| Datensatznummer |
250009712
|
| Publikation (Nr.) |
 copernicus.org/acp-11-4425-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
Aerosol samples were collected at a pasture site in the Amazon Basin as part
of the project LBA-SMOCC-2002 (Large-Scale Biosphere-Atmosphere Experiment
in Amazonia – Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass
Burning Perturb Global and Regional Climate). Sampling was conducted during the late dry
season, when the aerosol composition was dominated by biomass burning
emissions, especially in the submicron fraction. A 13-stage Dekati
low-pressure impactor (DLPI) was used to collect particles with nominal
aerodynamic diameters (Dp) ranging from 0.03 to 0.10 μm.
Gravimetric analyses of the DLPI substrates and filters were performed to
obtain aerosol mass concentrations. The concentrations of total, apparent
elemental, and organic carbon (TC, ECa, and OC) were determined using
thermal and thermal-optical analysis (TOA) methods. A light transmission
method (LTM) was used to determine the concentration of equivalent black
carbon (BCe) or the absorbing fraction at 880 nm for the size-resolved
samples.
During the dry period, due to the pervasive presence of fires in the region
upwind of the sampling site, concentrations of fine aerosols (Dp<2.5 μm:
average 59.8 μg m−3) were higher than coarse aerosols
(Dp> 2.5 μm: 4.1 μg m−3). Carbonaceous matter,
estimated as the sum of the particulate organic matter (i.e., OC × 1.8) plus
BCe, comprised more than 90% to the total aerosol mass.
Concentrations of ECa (estimated by thermal analysis with a correction
for charring) and BCe (estimated by LTM) averaged 5.2 ± 1.3 and
3.1 ± 0.8 μg m−3, respectively. The determination of EC was
improved by extracting water-soluble organic material from the samples,
which reduced the average light absorption Ångström exponent of
particles in the size range of 0.1 to 1.0 μm from >2.0 to
approximately 1.2. The size-resolved BCe measured by the LTM showed a
clear maximum between 0.4 and 0.6 μm in diameter. The concentrations of
OC and BCe varied diurnally during the dry period, and this variation
is related to diurnal changes in boundary layer thickness and in fire
frequency. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|