Browsing by Author "Lobo, Adelaide"
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- Background Levels of Atmospheric Particle Matter Over the Northeast Atlantic OceanPublication . Rodrigues, A. F.; Fialho, Paulo; Lobo, Adelaide; Pio, Casimiro; Cerqueira, MárioUnderstanding the physical and chemical properties of marine aerosol particles is crucial because of the role these particles play in a number of atmospheric processes. Marine aerosols affect climate directly through scattering and absorption of radiation and indirectly as they can act as cloud condensation nuclei and thus influence the albedo of clouds. In addition, marine aerosol particles play an important role in the cycling of various elements through the atmosphere. Many aspects about the origin of marine aerosols and their impact on atmospheric processes are still poorly known ar present and this lack of understanding stems in part from the relatively few measurements which have been performed in the most pristine areas of the earth. In order to improve our knowledge about the marine aerosol and its formation we established a land-based aerosol sampling station on the western coast of Terceira island (Azores). Here we present the first measurements of a project of sampling atmospheric particulate matter which started in Spring of 1999 and will be extended for one year.
- Caracterização de alguns aniões presentes nos aerossóis da atmosfera do Atlântico Norte.Publication . Rodrigues, A. F.; Fialho, Paulo; Pio, Casimiro; Lobo, AdelaideOs aerossóis têm géneses e composições muito diferenciadas. Estes têm origem nas emissões naturais (por exemplo o spray marinho e as emissões vulcânicas) ou antropogénicas (por exemplo os processos de combustão). A caracterização física e química dos aerossóis, é importante para compreender a relação entre: a sua origem; os mecanismos de transporte difusivo das massas de ar atmosférico; os processos de nucleação associados à formação de nuvens; e os mecanismos de transformação química. O Arquipélago dos Açores, situado numa zona remota (longe das emissões poluentes do continente Europeu e Americano e com emissões locais desprezáveis), é o local ideal para a caracterização física e química das massas de ar que o atravessam. A sua atmosfera “limpa” permite o estudo do transporte a longas distâncias de poluentes entre os continentes europeu e americano. Neste contexto a massa de aerossol (previamente amostrada em fracções fina - diâmetros inferiores a 0,95 μm - e grosseira - diâmetros entre 0,95 μm e 10 μm) foi analisada, por cromatografia líquida de troca iónica, para determinar o seu teor em aniões cloreto, nitrato e sulfato.
- Chemical characterisation of marine aerosol in the AzoresPublication . Rodrigues, Félix; Pio, Casimiro; Fialho, Paulo; Lobo, Adelaide; Carvalho, A.; Cerqueira, MárioGround-level concentrations of particulate matter with less than 10μm in diameter were measured in Azores Archipelago, mid-North Atlantic Ocean. Three intensive research campaigns took place between April and August 99. Observed average concentrations were 3.28±2.16 μgmˉ³ for non-sea-salt sulphate, 0.98±0.72μgmˉ³ for nitrate and 0.57±0.44μgmˉ³ for ammonium. The average value for non-sea-sulphate is higher than levels previously reported for other North Atlantic sites. The higher variability in non-sea-salt sulphate data collected in Azores Region most likely reflects a contribution due to active submarine volcanoes near the collection site (10–20 miles). We tried to make the connection between mass ratio sulphate/chloride maximums and maximum volcanic activity using seismic data. Average ratio between organic carbon and black carbon concentrations is 4.1±1.9.