Impact of biomass burning on aerosol physical-chemical properties in the Brazilian Pantanal

Abstract:

The Brazilian Pantanal is a complex landscape of great importance for the control of water flow in the Paraguay River Basin with growing agricultural and livestock production. The region has been impacted by deforestation and fires, emitting a crescent amount of biomass burning aerosols to the atmosphere with health and climate negative consequences. Aerosols collected with filters in the North Pantanal were analyzed chemically with Energy Dispersive X-Ray Fluorescence, and equivalent black carbon was quantified with a reflectometer. AERONET products such as Angstrom Exponents and Volumetric Size distribution were used to optically characterize aerosols over a seven month period during the dry season. Aerosols were also classified optically using Angström Matrix cluster analysis, that plots Absorption Angstrom Exponent (AAE) versus and Scattering Angstrom Exponent (SAE), and chemically relating their probable sources to verify the relation between chemical and optical characteristics. Results indicate a dominance of coarse particles related to biogenics (P, K and Mg at coarse mode) and crustal elements (Al, Si, Ca and Fe) at the beginning of the dry season, and finer elemental carbon and biomass burning elements (S, Zn and K at fine mode) at the end of the season. The optical classification shows a seasonally variation of more frequent groups, at the early dry season, species at low AAE e SAE were predominant has been labeled as Coated Large Particles and Biogenic, and in the advanced winter and beginning of Spring, the classes related to the elemental carbon as EC, EC/OC and Dust/EC with higher AAE and SAE. This is consequence of reduction of particle size and increase of organic and elemental carbon in the aerosols microstructure. There is a qualitatively relation between the optical and chemical classification, and the frequency of elemental and organic carbon groups was related qualitatively to the black carbon concentration at the filters. These results indicate that the aerosol composition and optical properties of the atmosphere during the dry season were impacted by land cover change, biomass burning, and fossil fuel emissions from Cuiaba, located more than 100 km away. These data highlight the importance of human impacts and long-range transport to the regional haze measured in the Northern Pantanal.