Contributions of biomass-burning, urban, and biogenic emissions to the concentrations and light-absorbing properties of particulate matter in central Amazonia during the dry season

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de Sa, Suzane S. ^[1] ; Rizzo, Luciana V. ^[2] ; Palm, Brett B. ^{[3, 4, 5]} ; Campuzano-Jost, Pedro ^{[3, 5]} ; Day, Douglas A. ^{[3, 5]} ; Yee, Lindsay D. ^[6] ; Wernis, Rebecca ^[7] ; Isaacman-VanWertz, Gabriel ^{[6, 8]} ; Brito, Joel ^{[9, 10]} ; Carbone, Samara ^{[9, 11]} ; Liu, Yingjun J. ^{[1, 12]} ; Sedlacek, Arthur ^[13] ; Springston, Stephen ^[13] ; Goldstein, Allen H. ^[6] ; Barbosa, Henrique M. J. ^[9] ; Alexander, M. Lizabeth ^[14] ; Artaxo, Paulo ^[9] ; Jimenez, Jose L. ^{[3, 5]} ; Martin, Scot T. ^{[1, 15]}

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^[1] Harvard Univ, John A Paulson Sch Engn & Appl Sci, Cambridge, MA 02138 - USA

^[2] Univ Fed Sao Paulo, Dept Environm Sci, Diadema, SP - Brazil

^[3] Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 - USA

^[4] Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 - USA

^[5] Univ Colorado, Dept Chem, Boulder, CO 80309 - USA

^[6] Univ Calif Berkeley, Dept Environm Sci Policy & Management, Berkeley, CA 94720 - USA

^[7] Univ Calif Berkeley, Dept Civil & Environm Engn, Berkeley, CA 94720 - USA

^[8] Virginia Tech, Dept Civil & Environm Engn, Blacksburg, VA - USA

^[9] Univ Sao Paulo, Inst Phys, Sao Paulo - Brazil

^[10] Univ Lille, SAGE, IMT Lille Douai, Lille - France

^[11] Univ Fed Uberlandia, Agr Sci Inst, Uberlandia, MG - Brazil

^[12] Peking Univ, Coll Environm Sci & Engn, Beijing - Peoples R China

^[13] Brookhaven Natl Lab, Upton, NY 11973 - USA

^[14] Pacific Northwest Natl Lab, Environm Mol Sci Lab, Richland, WA 99352 - USA

^[15] Harvard Univ, Dept Earth & Planetary Sci, 20 Oxford St, Cambridge, MA 02138 - USA

• Tipo de documento: Artigo Científico
• Fonte: Atmospheric Chemistry and Physics; v. 19, n. 12, p. 7973-8001, JUN 18 2019.
• Citações Web of Science: 2

Resumo

Urbanization and deforestation have important impacts on atmospheric particulate matter (PM) over Amazonia. This study presents observations and analysis of PM1 concentration, composition, and optical properties in central Amazonia during the dry season, focusing on the anthropogenic impacts. The primary study site was located 70 km downwind of Manaus, a city of over 2 million people in Brazil, as part of the GoAmazon2014/5 experiment. A high-resolution time-of-flight aerosol mass spectrometer (AMS) provided data on PM1 composition, and aethalometer measurements were used to derive the absorption coefficient b(abs,BrC) of brown carbon (BrC) at 370 nm. Non-refractory PM1 mass concentrations averaged 12.2 mu g m(-3) at the primary study site, dominated by organics (83 %), followed by sulfate (11 %). A decrease in b(abs,BrC) was observed as the mass concentration of nitrogen-containing organic compounds decreased and the organic PM1 O : C ratio increased, suggesting atmospheric bleaching of the BrC components. The organic PM1 was separated into six different classes by positive-matrix factorization (PMF), and the mass absorption efficiency E-abs associated with each factor was estimated through multivariate linear regression of b(abs,BrC) on the factor loadings. The largest E-abs values were associated with urban (2.04 +/- 0.14 m(2) g(-1)) and biomass-burning (0.82 +/- 0.04 to 1.50 +/- 0.07 m(2)g(-1)) sources. Together, these sources contributed at least 80 % of b(abs,BrC) while accounting for 30 % to 40 % of the organic PM1 mass concentration. In addition, a comparison of organic PM1 composition between wet and dry seasons revealed that only part of the 9-fold increase in mass concentration between the seasons can be attributed to biomass burning. Biomass-burning factor loadings increased by 30-fold, elevating its relative contribution to organic PM1 from about 10 % in the wet season to 30 % in the dry season. However, most of the PM1 mass (> 60 %) in both seasons was accounted for by biogenic secondary organic sources, which in turn showed an 8-fold seasonal increase in factor loadings. A combination of decreased wet deposition and increased emissions and oxidant concentrations, as well as a positive feedback on larger mass concentrations are thought to play a role in the observed increases. Furthermore, fuzzy c-means clustering identified three clusters, namely ``baseline{''}, ``event{''}, and ``urban{''} to represent different pollution influences during the dry season. The baseline cluster, representing the dry season background, was associated with a mean mass concentration of 9 +/- 3 mu g m(-3). This concentration increased on average by 3 mu g m(-3) for both the urban and the event clusters. The event cluster, representing an increased influence of biomass burning and long-range transport of African volcanic emissions, was characterized by remarkably high sulfate concentrations. The urban cluster, representing the influence of Manaus emissions on top of the baseline, was characterized by an organic PM1 composition that differed from the other two clusters. The differences discussed suggest a shift in oxidation pathways as well as an accelerated oxidation cycle due to urban emissions, in agreement with findings for the wet season. (AU)

• Processo FAPESP: 13/50510-5 - Pesquisa colaborativa Brasil-EUA: modificações causadas pela poluição antrópica na química da atmosfera e na microfísica de partículas da floresta tropical durante as campanhas intensivas do GoAmazon
• Beneficiário: Henrique de Melo Jorge Barbosa
• Linha de fomento: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Regular
• Processo FAPESP: 13/10156-8 - Perfis verticais de O3 e SO2 em um sítio de floresta preservada na Amazônia
• Beneficiário: Luciana Varanda Rizzo
• Linha de fomento: Auxílio à Pesquisa - Regular
• Processo FAPESP: 13/05014-0 - GoAmazon: interação da pluma urbana de Manaus com emissões biogênicas da Floresta Amazônica
• Beneficiário: Paulo Eduardo Artaxo Netto
• Linha de fomento: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático