Browsing by Author "Pio, Casimiro"
Now showing 1 - 10 of 20
Results Per Page
Sort Options
- 7Be as a tracer on the investigation of upper tropospheric dispersion of Saharan dust during the mid-winter 2000 storm events (Azores).Publication . Rodrigues, A. F.; Holmes, Charles; Pio, Casimiro; Marot, Marci; Fialho, Paulo7Be is a nuclide that acts like a tracer of input from the stratosphere and upper troposphere, where it is produced by spallation processes of light atmospheric nuclei such as nitrogen 14, oxygen 16 and carbon 12, with protons and neutrons (Zanis et al. 2000). By measuring the activity of beryllium isotopes attached to submicrometer aerosol particles, information on the mechanisms of exchange between the stratosphere and troposphere is obtained. […].
- Aerosol optical properties at Santiago Island, Cape Verde.Publication . Cerqueira, Mário; Pio, Casimiro; Fialho, Paulo; Cardoso, João; Nunes, Teresa; Almeida, S. M.> huge amounts of mineral dust are emitted every year from the Sahara desert to the atmosphere; > optical parameters of mineral aerosols determine the direct interaction of solar and terrestrial radiation in the atmosphere through scattering and absorption; > mineral dust has a great impact on cloud formation leading to additional indirect radiation effects; > The dense haze from dust events is also known to affect visibility.
- Amostragem de partículas em suspensão na atmosfera do Atlântico Norte.Publication . Rodrigues, A. F.; Fialho, Paulo; Pio, CasimiroOs 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 localizado 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 americano e europeu. Neste contexto efectuou-se a caracterização física do aerossol, recorrendo a um colector de partículas de grande volume (High-Volume - figura 1) com uma cabeça de pré-selecção de 10 μm. Os aerossóis foram separados em duas fracções, uma fina (diâmetros inferiores a 10 μm) essencialmente associada a contribuições antropogénicas, e outra grosseira (diâmetros entre 0,95 μm e 10 μm) maioritariamente relacionada com contribuições naturais. A massa de aerossol amostrada é determinada pela pesagem dos filtros onde este é recolhido, conjuntamente são efectuadas medidas de caudal volúmico e tempo de amostragem.
- The application of a multi-wavelength Aethalometer to estimate iron dust and black carbon concentrations in the marine boundary layer of Cape VerdePublication . Fialho, Paulo; Cerqueira, Mário; Pio, Casimiro; Cardoso, João; Nunes, Teresa; Custódio, Danilo; Alves, Célia A.; Almeida, S. M.; Almeida-Silva, M.; Reis, M. A.; Rocha, F.The two-component model (Fialho et al., 2006) was used to decouple the contributions of black carbon (BC) and iron oxides, present in dust, to the aerosol attenuation coefficient, measured with a multiwavelength Aethalometer. The model results were compared with the elemental carbon (EC) and iron concentrations determined in the laboratory from the analysis of aerosol particles collected with conventional samplers. The comparison was based on one year of data obtained at Praia, Santiago Island, Cape Verde, after side by side operation of the aerosol monitoring instruments. The linear regression equation that best describes the relationship between BC concentrations, derived from the Aethalometer, and EC concentrations, derived from a PM10 high-volume sampler after filter analysis with a thermal optical method, presents a slope of 1.01 ± 0.05 and a correlation coefficient (r) of 0.90, showing that the model worked as intended to describe BC concentrations without interferences from iron dust. On the other hand, the linear regression equation that best describes the relationship between the iron concentrations derived from the Aethalometer and elemental iron concentrations, derived from a PM10 lowvolume sampler after filter analysis by k0 e Instrumental Neutron Activation Analysis, presents a slope of 0.495 ± 0.014 and a correlation coefficient (r) of 0.96. These results show that the two-component model underestimated the iron concentrations in dust aerosol, which was explained by differences in the size range of particles sampled with the Aethalometer and the PM10 low-volume sampler together with differences in the size distribution of iron oxides.
- Assessment of air quality on basis of particle matter (PM) measurement in the North Atlantic.Publication . Barata, Filipe; Fialho, Paulo; Pio, CasimiroThe European thematic strategy on air pollution and the accompanying proposal to revise the ambient air quality directive (1999/30/EC) would, for the first time, introduce controls on human expose to PM2.5 to complement the existing limits on coarse particulate matter (PM10) (EC, 2005).
- 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.
- Characterisation of carbonaceous aerosols from the Azorean island of TerceiraPublication . Alves, Célia A.; Oliveira, Tiago S.; Pio, Casimiro; Silvestre, Armando J. D.; Fialho, Paulo; Barata, Filipe; Legrand, MichelAerosol samples were collected from 2002 to 2003 in Terceira, one of the islands of the Azores archipelago in the north-eastern Atlantic. The atmospheric samples have been analysed for its carbonaceous content and for lipid class compounds. The major constituents that comprise plant wax are n-alkanes (C23–C33, with and odd-to-even carbon predominance and carbon maxima at 29 or 31), n-alkanols (C22–C30, even-to-odd) and n-alkanoic acids (C22–C30, even-to-odd), with minor amounts of n-alkanals and polycyclic biomarkers, such as phytosterols. Some alkanedioic acids and phthalates were also detected. The occurrence of short-chain homologues may indicate an additional marine source, probably introduced into the atmosphere via sea spray. Changes in the composition of the homologous series derived from terrestrial plants throughout the observation period may be related to alterations in the regional sources and transport pathways. These terrestrial lipids contributed up to 47% of the total compound mass, while the marine input was estimated to be inferior to 19%, both of them being more representative in summer. Biomass burning sources represented approximately 1% of the total inputs to the organic aerosol for the most part of the year, excepting during the spring, when it contributed to 10%. Petroleum products and plasticizers presented higher contributions (up to 19%) during the winter months. Secondary constituents resulting from oxidation during transport varied from 14% to 37% of the apportioned organic mass. The fraction derived from soil resuspension accounted for 2–16%.
- 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.
- Climatology of aerosol composition (organic versus inorganic) at nonurban sites on a west-east transect across EuropePublication . Pio, Casimiro; Legrand, Michel; Oliveira, Tiago S.; Afonso, Joana; Santos, C.; Caseiro, A.; Fialho, Paulo; Barata, Filipe; Puxbaum, Hans; Sanchez-Ochoa, A.; Kasper-Giebl, Anne; Gelencsér, András; Preunkert, Susanne; Schock, M.In the framework of the European CARBOSOL project (Present and Retrospective State of Organic versus Inorganic Aerosol over Europe: Implications for Climate), atmospheric aerosol was continuously sampled for 2 years at six sites along a west-east transect extending from Azores, in the mid-Atlantic Ocean, to K-Puszta (Hungary), in central Europe. Aerosols were analyzed for ²¹°Pb, inorganic ions, elemental (EC) and organic (OC) carbon, water soluble organic carbon (WSOC), macromolecular type (humic-like) organic substances (HULIS), C2–C5 diacids, cellulose, and levoglucosan. Pooled aerosol filters were also used for the identification of different families of organic compounds by gas chromatography/mass spectrometry, GC/MS, as well as 14C determinations. The data resulted in a climatological overview of the aerosol composition over Europe in the various seasons, from west to east, and from the boundary layer to the free troposphere. The paper first summarizes the characteristics of the sites and collected samples and then focuses on the aerosol mass partitioning (mass closure, inorganic versus organic, EC versus OC, water soluble versus insoluble OC), giving an insight on the sources of carbonaceous aerosol present in rural and natural background areas in Europe. It also introduces the main role of other companion papers dealing with CARBOSOL aerosol data that are also presented in this issue.