Overview of the inorganic and organic composition of size-segregated aerosol in Rondônia, Brazil, from the biomass-burning period to the onset of the wet season

The aerosol characterization experiment performed within the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia–Smoke, Aerosols, Clouds, Rainfall and Climate (LBA‐SMOCC) field experiment carried out in Rondônia, Brazil, in the period from September to November 2002 provides a unique data set of...

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Published in:Journal of Geophysical Research - Atmospheres 2007-01, Vol.112 (D1), p.D01201-n/a
Main Authors: Fuzzi, Sandro, Decesari, Stefano, Facchini, Maria Cristina, Cavalli, Fabrizia, Emblico, Lorenza, Mircea, Mihaiela, Andreae, Meinrat O., Trebs, Ivonne, Hoffer, András, Guyon, Pascal, Artaxo, Paulo, Rizzo, Luciana V., Lara, Luciene L., Pauliquevis, Theotonio, Maenhaut, Willy, Raes, Nico, Chi, Xuguang, Mayol-Bracero, Olga L., Soto-García, Lydia L., Claeys, Magda, Kourtchev, Ivan, Rissler, Jenny, Swietlicki, Erik, Tagliavini, Emilio, Schkolnik, Gal, Falkovich, Alla H., Rudich, Yinon, Fisch, Gilberto, Gatti, Luciana V.
Format: Article
Language:English
Subjects:
aerosol chemical composition
Atmospheric Composition and Structure
biomass burning
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fysik
Global Change
Natural Sciences
Naturvetenskap
organic aerosol
Physical Sciences
Pollution
Remote sensing
Subatomic Physics
Subatomär fysik
urban and regional
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Summary:The aerosol characterization experiment performed within the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia–Smoke, Aerosols, Clouds, Rainfall and Climate (LBA‐SMOCC) field experiment carried out in Rondônia, Brazil, in the period from September to November 2002 provides a unique data set of size‐resolved chemical composition of boundary layer aerosol over the Amazon Basin from the intense biomass‐burning period to the onset of the wet season. Three main periods were clearly distinguished on the basis of the PM10 concentration trend during the experiment: (1) dry period, with average PM10 well above 50 μg m−3; (2) transition period, during which the 24‐hour‐averaged PM10 never exceeded 40 μg m−3 and never dropped below 10 μg m−3; (3) and wet period, characterized by 48‐hour‐averaged concentrations of PM10 below 12 μg m−3 and sometimes as low as 2 μg m−3. The trend of PM10 reflects that of CO concentration and can be directly linked to the decreasing intensity of the biomass‐burning activities from September through November, because of the progressive onset of the wet season. Two prominent aerosol modes, in the submicron and supermicron size ranges, were detected throughout the experiment. Dry period size distributions are dominated by the fine mode, while the fine and coarse modes show almost the same concentrations during the wet period. The supermicron fraction of the aerosol is composed mainly of primary particles of crustal or biological origin, whereas submicron particles are produced in high concentrations only during the biomass‐burning periods and are mainly composed of organic material, mostly water‐soluble, and ∼10% of soluble inorganic salts, with sulphate as the major anion. Size‐resolved average aerosol chemical compositions are reported for the dry, transition, and wet periods. However, significant variations in the aerosol composition and concentrations were observed within each period, which can be classified into two categories: (1) diurnal oscillations, caused by the diurnal cycle of the boundary layer and the different combustion phase active during day (flaming) or night (smouldering); and (2) day‐to‐day variations, due to alternating phases of relatively wet and dry conditions. In a second part of the study, three subperiods representative of the conditions occurring in the dry, transition, and wet periods were isolated to follow the evolution of the aerosol chemical composition as a function of changes in rainfall rate and in
ISSN:0148-0227
2156-2202
2156-2202
DOI:10.1029/2005JD006741