IDL-UBI | Instituto Dom Luiz
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IDL-UBI develop their research activities in several topics: Climate Change, atmosphere-land-ocean processes and extremes; Solid Earth dynamics, hazards and resources; GeoInformatics.
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- Absorption coefficients of aerosols obtained from in situ data in Covilhã, central PortugalPublication . Mogo, Sandra; Cachorro, Victoria; De Frutos, Ángel MSince October 2009 an aerosol measurement data set was started at Covilhã, a small town located in the region of Beira Interior (Portugal) ain the interior a of the Iberian Peninsula. a Until July 2010, the ambient light-absorption coefficient, σ (470 nm), σ (522 nm) and σ (660 nm), presented a daily mean value of 14.2Mm-1 (StD=8.6Mm-1), 12.1Mm-1 (StD=7.3Mm-1) and 9.6Mm-1 (StD=5.7Mm-1), respectively. Monthly variations and daily cycle are presented in this work.
- In situ UV-VIS-NIR absorbing properties of atmospheric aerosol particles: Estimates of the imaginary refractive index and comparison with columnar valuesPublication . Mogo, Sandra; Cachorro, Victoria; de Frutos, Ángel MIn this work, a novel technique is used to estimate the aerosol complex index of refraction of in situ collected samples. Samples of atmospheric particulate matter were collected in El Arenosillo, southern Spain, on polycarbonate filters during summer 2004 as part of an aerosol characterization campaign. These samples were analyzed for the volumetric absorption coefficient in the 320e800 nm spectral region and an estimation of the effective imaginary refractive index was made. The values of the imaginary part of the complex refractive index ranged between 0.0009e0.0215 at 800 nm and 0.0015e0.0114 at 320 nm. Little dependence on the wavelength was observed. Several intense and long lasting desert outbreaks were registered during the campaign and the complex refractive index almost doubles its value during these dust events. Finally, we present a comparison of data obtained in situ with columnar data obtained from the AERONET network. A correlation factor of 0.64 was obtained between both data, which gives an idea of how accurately the in situ ground data represent the total column.
- Absorption Ångström exponents of aerosols and light absorbing carbon (LAC) obtained from in situ data in Covilhã, central PortugalPublication . Mogo, Sandra; Cachorro, Victoria; de Frutos, Ángel M; Rodrigues, A.A field campaign was conducted from October 2009 to July 2010 at Covilhã, a small town located in the region of Beira Interior (Portugal) in the interior of the Iberian Peninsula. The ambient light-absorption coefficient, σ(a) (522 nm), obtained from a Particle Soot Absorption Photometer (PSAP), presented a daily mean value of 12.1 Mm⁻¹ (StD = 7.3 Mm⁻¹). The wavelength dependence of aerosol light absorption is investigated through the Ångström parameter, α(a). The α(a) values for the pair of wavelengths 470-660 nm ranged from 0.86 to 1.47 during the period of measurements. The PSAP data were used to infer the mass of light absorbing carbon (LAC) and the daily mean varied from 0.1 to 6.8 μg m⁻³. A detailed study of special events with different aerosol characteristics is carried out and, to support data interpretation, air masses trajectory analysis is performed.
- In situ measurements of aerosol optical properties and number size distributions in a coastal region of Norway during the summer of 2008Publication . Mogo, Sandra; Cachorro, Victoria; Lopez, J. F.; Montilla, E.; Torres, B.; Rodríguez, E.; Bennouna, Y.; de Frutos, Ángel MAbstract. In situ measurements of aerosol optical properties and particle size distributions were made in the summer of 2008 at the ALOMAR station facility (69◦160 N, 16◦ 000 E), located in a rural site in the north of the island of Andøya (Vesterålen archipelago), approximately 300 km north of the Arctic Circle. The extended three-month campaign was part of the POLARCAT Project (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) of the International Polar Year (IPY-2007-2008). Our goal was to characterize the aerosols of this sub-Arctic area, which are frequently transported to the Arctic region. Data from 13 June to 26 August 2008 were available and the statistical data for all instruments were calculated based on the hourly averages. The overall data coverage was approximately 72 %. The hourly mean values of the light-scattering coefficient, σs , and the light-absorption coefficient, σa, at 550 nm were 5.41 Mm−1 (StD = 3.55 Mm−1 ) and 0.40 Mm−1 (StD = 0.27 Mm−1 ), respectively. The scattering/absorption Ångström exponents, αs,a , were used in a detailed analysis of the variations of the spectral shape of σs,a. While αs indicates the presence of two particle sizes corresponding to two types of aerosols, αa indicates only one type of absorbing aerosol particle. αa values greater than 1 were not observed. The single-scattering albedo, ω0 , ranged from 0.62 to 0.99 (mean = 0.91, StD = 0.05), and the relationships between this parameter and the absorption/scattering coefficients and the Ångström exponents are presented. Any absorption value may lead to the lowest values of ω0 , whereas only the lowest scattering values were observed in the lowest range of ω0 . For a given absorption value, lower ω0 were observed for smaller αs. The submicrometer, micrometer and total concentrations of the particles presented hourly mean values of 1277 cm−3 (StD = 1563 cm−3), 1 cm−3 (StD = 1 cm−3) and 2463 cm−3 (StD = 4251 cm−3), respectively, and the modal correlations were also investigated. The optical and microphysical parameters, as well as their relationship with each other, are reported. σs correlated strongly with the number concentration of accumulation mode particles and more strongly with the micrometer fraction of particles, but weak correlations were observed for the Aitken and nucleation modes. The origins and pathways of the air masses were examined, and based on sector classification, a relationship between the air mass origin, the optical parameters and the size distributions was established. The low values of the optical and microphysical parameters indicate that the predominant regional aerosol is mostly clean and the shape of the size distribution is characterized by bimodal median size distributions. However, the relationships between the air mass origins and the parameters studied allow us to describe two characteristic situations: the one of the northern and western air masses, which were predominantly composed of marine aerosols and presented the lowest optical and microphysical values observed, indicating predominantly non-absorbent and coarser particles; and the one of the eastern and southern air masses, in which continental aerosols were predominant and exhibited higher values for all parameters, indicating the presence of smaller absorbent particles. The north-northeastern air masses presented the strongest Aitken mode, indicating more recently formed particles, and the southeastern air masses presented the strongest accumulation mode (however, the southeastern air masses were the least common, accounting for only 3 % of occurrences).
- Atmospheric particulate matter levels, chemical composition and optical absorbing properties in Camagüey, CubaPublication . Barja, Boris; Mogo, Sandra; Cachorro, Victoria; Antuña, Juan Carlos; Estevan, Rene; Rodrigues, Ana; de Frutos, Ángel MAtmospheric aerosol particles were collected at Camagüey, Cuba, during the period from February 2008 to April 2009 in order to know the particulate matter levels (PM) together with a general chemical and absorption characterization. The aerosols collection was carried out with a low volume particulate impactor twice a week. Gravimetric analysis of the particulate matter fractions PM10 and PM1 was carried out. An analysis of the eight major inorganic species (Na+, K +, Ca2+ , Mg2+, NH4+, Cl , NO3 and SO42 ) using ionic chromatography was conducted. The results were analyzed in two periods, the high aerosol concentration period (May to August) and the period with low aerosol concentration (the other months). During the high concentration period the average PM10 and PM1 levels were 35.11 mg m 3 (std 1⁄4 15.45 mg m 3) and 16.86 mg m 3 (std 1⁄4 6.14 mg m 3). During the low concentration period the average PM10 and PM1 levels were 23.13 mg m 3 (std 1⁄4 5.00 mg m 3) and 13.00 mg m 3 (std 1⁄4 4.02 mg m 3). For both periods, Cl , Na+ and NO3 are the predominant species in the coarse fraction (PM1-10), and SO42 and NH4+ are the predominant species in the fine fraction (PM1). The spectral aerosol absorption coefficient, sa, was measured for the wavelength range 400–700 nm with 10 nm steps. The sa values were obtained with a filter transmission method for the fine fraction and were evaluated for 54 days covering a wide range of atmospheric conditions including a Saharan dust intrusion. sa ranges from 8.5 M m 1 to 34.5 M m 1 at a wavelength of 550 nm, with a mean value of 18.7 M m 1. The absorption Ångström parameter, aa, calculated for the pair of wavelengths (450/700 nm) presents a mean value of 0.33 (std 1⁄4 0.19), which is a very low value comparing with those that can be found in the bibliography. Although the sampling period is short, these data represent the first evaluation of PM values with their chemical and optical absorption characterization in Cuba. In addition to the regional interest, the presented values can be directly used by those working with absorption, forcing by aerosols and radiative transfer calculations in general. Also, these data can be used as input in Global Climate Models.
- Comparison between the optical properties of aerosols in the fine and coarse fractions over Valladolid, SpainPublication . Mogo, Sandra; López, J. F.; Cachorro, Victoria; de Frutos, Ángel M; Zocca, Renan Oliveira; Barroso, Ana; Mateos, D.; Conceição, E.Continuous measurements of the optical properties of aerosol particles have been made at Valladolid, Spain, covering the period from June 2011 to July 2012. The measurements were made at two size cuts: sub-10 μm and sub-1 μm (PM10 and PM1). The data measured were the scattering and backscattering coefficients, σs and σbs, obtained from an integrating nephelometer, and the absorption coefficient, σa, obtained from a particle soot absorption photometer. Spectrally resolved data were obtained from both instruments at 3 wavelengths (blue/green/red) at low relative humidity (RH < 40%). The statistical data for the instruments were calculated based on the hourly averages. For the PM10 fraction, the hourly mean values of σs and σa at 550 nm were 33 Mm−1 (StD = 30 Mm−1) and 4 Mm−1 (StD = 3 Mm−1), respectively. For the PM1 fraction, σs and σa mean values were 16 Mm−1 (StD = 14 Mm−1) and 4 Mm−1 (StD = 3 Mm−1), also at 550 nm. The derived parameters analyzed were the single scattering albedo, ω0, the backscatter fraction, σbs/σs, and the Ångström exponents of scattering, absorption and single scattering albedo, αs, αa and αω0. The contribution of the PM10 and the PM1 fractions for all these parameters plays a central role throughout the paper, allowing an improved classification of aerosol types. Our data are dominated by elemental carbon (EC) and elemental carbon/organic carbon mixed (EC/OC). For the PM10 data, dust dominated aerosol is also observed. Although we found that fine particles contribute more than coarse particles for decreasing the ω0 values, results suggest that it is also necessary to quantify the effect of coarse particles. Fine particles were found to produce ω0 spectra that decrease with the wavelength, αω0 > 0, while PM10 fractions were found to produce spectra that can decrease or increase with the wavelength, 0 < αω0 < 0. Both daily cycle and monthly variations are analyzed and related to local features as well as the transport of particles from elsewhere. A diurnal pattern characteristic of urban areas is observed, but it is less evident on weekends. The main long range transport influences are Atlantic advection, anthropogenic events from Central Europe and dust events.
- Morphology, Mineralogy, and Chemistry of Atmospheric Aerosols Nearby an Active Mining Area: Aljustrel Mine (SW Portugal)Publication . Barroso, Ana; Mogo, Sandra; Silva, M. Manuela V. G.; Cachorro, Victoria; De Frutos, Ángel MMining activities increase contaminant levels in the environment, so it is crucial to study the particulate matter in these areas to understand the impacts on nearby urban areas and populations. This work was conducted close to the active mine of Aljustrel (Portugal), where black dust deposition is evident. PM10 samples were collected in two periods: 10–17 July and 1–10 November of 2018. Two different techniques were used: SEM-EDX for the individual characterization of the aerosols and ICP-MS to quantify the elemental concentration of 11 elements (Ca, Na, Fe, Mn, As, Cd, Cu, Sb, Pb, and Zn). In this region, the observed PM10 mass concentration was 20 to 47 g m 3 (July) and 4 to 23 g m3 (November), which is lower than the limit of 50 g m3 established in the European Directive. The individual characterization of 2006 particles by SEM-EDX shows oxides (17%) and sulfides (10%), while Na, Si, Fe, S, Al, and Cu are the elements with the most representativeness in all the analyzed particles. The ICP-MS results indicate that the daily elemental concentration in the samples collected in July is higher than November, and only As exceeds the limit established for European legislation.