Browsing by Author "Freitas, Maria do Carmo"
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- Additions to the lichen flora found on Cryptomeria japonica D. Don, in the Azores.Publication . Rodrigues, António F.; Aptroot, André; Freitas, Maria do Carmo; Sousa, Eva; Rodrigues, Carla; Amaral, Ana Sofia; Vieira, Bruno; Soares, PaulaTwenty-nine lichens species were reported in samples from Azorean Cryptomeria japonica forests. One species, Ramalina peruviana Ach., is newly recorded for the Macaronesian Region. On Cryptomeria japonica, seven new lichen records were found for the Azores: Parmotrema bangii (Vain.) Hale, Pyrrospora quernea (Dickson) Körber, Pyxine subcinerea Stirt., Ramalina implectens Nyl., Ramalina peruviana Ach., Usnea dasaea Stirton and Usnea esperantiana P. Clerc.The species Ramalina peruviana Ach., is rare within the Macaronesian Region.
- Aerosol chemical elemental mass concentration at lower free tropospherePublication . Freitas, Maria do Carmo; Dionísio, Isabel; Fialho, Paulo; Barata, FilipeThis paper shows the use of Instrumental neutron activation analysis (INAA) technique to determine elemental masses collected by a seven-wavelength Aethalometer instrument at the summit of Pico mountain in the Azorean archipelago, situated in the Central North Atlantic Ocean. Each sample corresponds to air particulate matter measured continuously for periods of approximately 24 h taken from 14th July 2001 through 14th July 2002. The statistical analysis of the coefficients of correlation between all the elements identified, permitted to establish six groups that could potentially be associated with the type of source responsible for the aerosol sampled in the lower free troposphere at the Azorean archipelago. Calculation of the synoptic back trajectories helped to corroborate the use of the iron/cesium relation as a tracer for the Saharan dust aerosol. It was demonstrated that INAA constituted an important tool to identify these events.
- Comparison of continental Portugal and Azores Islands aerosol during a Sahara dust stormPublication . Reis, M. A.; Oliveira, O. R.; Alves, L. C.; Rita, E. M.; Rodrigues, Félix; Fialho, Paulo; Pio, Casimiro; Freitas, Maria do Carmo; Soares, J. C.Airborne particulate matter plays an important role in the Earth's energy balance. One of the main reasons is that the real size of a significant number of the particles, mainly those of anthropogenic origin, is similar to the wavelength of visible light. Knowledge of the composition of such particles, as well as their dynamics and trajectories in the atmosphere is therefore very important. In the period from 23 February to 22 March 2000, a movement of airborne particulate matter going over Europe and towards Azores was identified based on satellite observation. This work presents a preliminary study based on PIXE and nuclear micro-probe analysis of samples collected during that period both in Portugal mainland and in Terceira Island in the Azores. Time-shifted correlation of sample composition and individual particle composition are presented and discussed. Results point to the possibility of inferring long-range transport of aerosol particles from the samples multi-element analysis, and to the existence of fractions of the North Atlantic aerosol identical at both Portugal mainland and Terceira Island.
- Lower Free Troposphere Aerosol Elemental Composition at Central North Atlantic Region.Publication . Freitas, Maria do Carmo; Fialho, Paulo; Pacheco, Adriano M. G.; Pio, Casimiro; Tuncel, GurdalAerosol samples were collected using an aethalometer (AE31) from 15 July 2001 to the present at the Pico Mountain site in Pico island, Azores, Portugal (38.470ºN; 28.404ºW and 2225 m above mean see level). The aethalometer was setup to integrate the aerosol samples for 24 h period for most of the cases, with the exception of the period between July 2002 and July 2003 were it was leaved to change the integration sample spot only after 75% attenuation level. [...].
- Seasonal Variability of Atmospheric Dust Over Cape Verde Islands.Publication . Pio, Casimiro; Freitas, Maria do Carmo; Cardoso, João; Nunes, Teresa; Almeida, S. M.; Almeida, Marta; Tchepel, O.; Rocha, F.; Cerqueira, Mário; Ferreira, F.; Terroso, D.; Fialho, Paulo; Dung, Ho; Custódio, Danilo
- The Aethalometer calibration and determination of iron concentration in dust aerosolsPublication . Fialho, Paulo; Freitas, Maria do Carmo; Barata, Filipe; Vieira, Bruno; Hansen, Anthony; Honrath, RichardThis paper shows the use of the instrumental neutron activation analysis (INAA) technique to calibrate Aethalometer instruments’ response to iron oxides present in Saharan dust aerosol. The five samples selected for this calibration were collected with a seven-wavelength Aethalometer (model AE31) at the summit of Pico mountain (2225 m ASL) in the Azores Islands. These samples correspond to measurements taken between the 31 October and 5 November, 2001. Analysis of these samples by the INAA technique gave a total mass of 14.84 ± 0.70 μg (Fe). Correlation of the analytical results with the optical measurements allowed the determination of the elemental iron calibration constant, KFe (0.234 ±0.022 μm4 m² gˉ¹), which can be used in the determination of iron concentrations from multi-wavelength Aethalometer measurements. As an example of this, we used Aethalometer measurements during the 2001 event to calculate hourly average dust iron, 〈CFe〉, concentrations, which range from 0.00 and 1.77 μg (Fe) mˉ³.