Estudo de material particulado fino utilizando ToF-ACSM no sítio ATTO na Bacia Central da Amazônia durante o período de janeiro a julho de 2017

Abstract

The Amazon Basin plays important roles in biogeochemical cycles, climate change, atmospheric chemistry and biodiversity. In addition, during the wet season it serves as an ideal place to study the formation of atmospheric particles, as it often represents quasi-natural, pre-industrial conditions, however, it can also experience long periods of anthropogenic and/or African Continent influence, range transport (LRT). This work aimed to analyze the chemical composition of the submicrometric aerosol (PM1) and identify the chemical classes present in the organic fraction of PM1, by means of positive matrix factorization (PMF) during the wet (WP) and transition (TP) period of 2017, in the central Amazon basin, at the ATTO observation site. In order to better understand the properties of aerosol particles, the Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) was used to characterize its non-refractory fraction of the submicrometer aerosol and the Multiangle Absorption Photometer (MAAP) was used to measure the concentration of equivalent black carbon (eBC). The chemical composition of submicron aerosol particles was mostly organic (67% and 81%), sulfate (9% and 8%) and eBC (14% and 4%) in the PC and PT periods, respectively. A good correlation was observed in the diurnal profile of organics, sulfate, eBC and nitrate, with a higher concentration around 15h00 (local time), which must be related to the photochemical production of secondary aerosol particles. Two factors were identified through the PMF in the organic fraction of the aerosol, namely, OOA and IEPOX-SOA. During the entire period (WP+TP) OOA presented the largest contribution (63%), followed by IEPOX-SOA (37%). However, when the periods were run separately (WP+TP, WP and TP), the WP presented a contribution of OOA and IEPOX-SOA distributed more homogeneously (55% and 45%), while the contribution during the TP was similar to the results of the PC+PT period (76% and 24%, respectively). In both cases (WP+TP and WP, TP) the number of factors for the solutions was the same (2) and the mass spectra found were similar, suggesting that the PC+PT solution is adequate