Size-segregated particulate matter and carboxylic acids over urban and rural sites in Londrina City, Brazil

Abstract

Amostragens simultâneas de material particulado (PM) de 0,25 a 10 mm foram realizadas entre os meses de março e abril de 2007 em área urbana e rural de Londrina (Paraná). Os resultados indicaram que o material particulado fino (PM 2,5 ) representa uma significativa porção da massa de material particulado PM 10 (70 e 67% na área urbana e rural, respectivamente). Ácidos dicarboxílicos foram encontrados em maior concentração respondendo por 78% e 69% da massa de PM 2,5 na área urbana e rural, respectivamente, sendo que o oxalato e succinato foram os mais abundantes. A distribuição de massa do oxalato em área urbana apresentou picos dominantes em 0,25-0,5 µm. A razão de massa de acetato e formato indicou as emissões veiculares primarias como fonte dominante de ácidos carboxílicos em Londrina. Além disso, análises das trajetórias indicaram a ocorrência de transporte de poluentes do estado de São Paulo para a região de estudo.Samplings of atmospheric particulate matter (PM) from 0.25 to 10 µm were performed between the months of March and April 2007, simultaneously in urban and rural areas of Londrina City (Paraná State, Brazil). Results indicated that the fine fraction (PM 2.5 ) represents a significant portion of the PM 10 mass (70 and 67% in urban and rural areas, respectively). Dicarboxylic acids were found in larger concentration, contributing to the PM 2.5 fraction with 78% in urban and 69% in rural areas, being oxalate and succinate the most abundant species. Mass size distribution of oxalate in urban site was presented as the dominant mode, with peaks at 0.25-0.5 µm. Acetate-to-formate mass ratio indicated the primary vehicular emissions as dominant source of carboxylic acids in Londrina. Moreover, backward trajectories indicated the transport of pollutants from São Paulo State to Londrina region.Keywords: size-segregated particulate matter, carboxylic acids, PM 2.5 , urban and rural aerosols IntroductionThe occurrence and abundance of carboxylic acids in atmospheric particulate matter (PM) depend on meteorological conditions and characteristics of the ambient. The carboxylic acids represent a major fraction of the organic acids present in the atmospheric particulate matter. Among them, the oxalic acid has been the main species, followed by succinic and malonic acids. [1][2][3][4][5][6] Mono-and di-carboxylic acids are important groups of organic compounds identified in the atmospheric particles. 7,8 Formic and acetic acids, the dominant species of organic acids in tropospheric aqueous and gaseous phases, are also ubiquitous in aerosol particles. Oxalic acid has been detected as the major fraction of water-soluble organic compounds in urban, rural and even in remote areas. [3][4][5][6] Since carboxylic acids are highly water-soluble, they have the potential to modify the hygroscopic properties of atmospheric particles, including their ambient size and cloud condensation nuclei activity. 9,10 Weak organic acids could contribute ca. 40 and 60% to the free acidity in precipitation in urban and remote areas, respe...

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