B116-0028
FINE PARTICULATED MATERIAL USING TOF-ACSM AT ATTO STATION IN THE CENTRAL AMAZON BASIN: WET AND TRANSITION SEASONS 2017

Wednesday, 16 December 2020
Poster
Lucas Chiari1, Bruna A. Holanda2, Christopher Pöhlker2, Paulo Artaxo3 and Samara Carbone4, (1)Federal University of Uberlândia, Institute of Agrarian Sciences, Uberlândia, Brazil, (2)Max Planck Institute for Chemistry, Multiphase Chemistry Department, Mainz, Germany, (3)University of São Paulo, Physics Institute, São Paulo, Brazil, (4)Federal University of Uberlândia, Uberlândia, Brazil
Abstract:
The Amazon rainforest region has undergone changes in land use patterns due to human occupation. This study aims to analyze the chemical composition of the submicrometric aerosol particles (PM1) during the wet season (January to April) and transition (May to June) of 2017, in the central basin of the Amazon rainforest, at the ATTO site (The Amazon Tall Tower Observatory). The chemical composition of the PM1 was measured by the time-of-flight aerosol chemical speciation monitor (ToF-ACSM) and Multi-Angle Absorption Pothotometer (MAAP) from January to June of 2017. The wet season was defined based on the accumulated rainfall (Pac) from January to April (Pac = 2400 mm), the dry season from August to November (Pac = 407 mm) and the months left were defined as transition from May to June and December. It was observed that the organic, sulfate and eBC components represented the major PM1 fraction. On average the organic, sulfate and eBC fractions comprised 60, 12 and 18% of the PM1, respectively, during the wet and 76, 13 and 3% during the transition in 2017. These values are in line with previous studies for a central Amazon rainforest basin. In addition, the IEPOX-SOA tracer (f82) was clear and represented on average 0.95% of the organic aerosol (OA). In the wet season the average f82 was 0.91% with maximum reaching 6.5% of the OA. While in the transition the average f82 was 1.1% with maximum of 3.3%. The reason why f82 was higher in the transition is not clear, however it could be related to the sulfate mass concentration, which was 3 times higher in the transition (0.3 µg.m-3) than in wet season (0.3 µg.m-3), even though no significant mass fraction change was observed. The values of f82 as a proxy for IEPOX-SOA were higher during the transition season than in wet season. This difference in f82 values and the degree of oxidation of PM1 will be further studied through the PMF analysis.
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