Benito de la Morena

Carotenoids as protective response against oxidative damage in Dunaliella bardawil

In the present work the relation between carotenoids production and cell response mechanisms to oxidative damage was studied. High light intensity and nitrogen starvation, both conditions, which may increase the oxidative damage in microalgae, significantly increased total carotenoids content in Dunaliella bardawil, the effect of N-starvation being more noticeable when acting synergetically with light on carotenoid production. S-starvation stimulated carotenoids production as much as N-starvation. The use of norflurazon, inhibitor of phytoene desaturase that blocks formation of epsilon-carotene from phytoene, caused a decrease of carotenoid content down to 5% that of the control cells incubated without the inhibitor. The decrease in the oxygen consumption rate of D. bardawil cells exposed to norflurazon suggests a connection between carotenoids desaturation and chloroplastic oxygen species dissipation processes reported in the literature for other algae. It is an indication of the carotenoids involvement in chloroplastic response mechanisms to oxidative damage.

The Empirically Corrected EP-TOMS Total Ozone Data Against Brewer Measurements at El Arenosillo (Southwestern Spain)

This paper focuses on the validation of the empirically corrected total ozone column (TOC) data provided by the Earth Probe Total Ozone Mapping Spectrometer (EP-TOMS) using ground-based measurements recorded by a well-calibrated Brewer spectroradiometer located at El Arenosillo (Spain). In addition, satellite TOC observations derived from the Ozone Monitoring Instrument (OMI) with the TOMS algorithm are also used in this paper. The agreement between EP-TOMS TOC data and Brewer measurements is excellent (R2 ~ 0.92) even for the period 2000-2005 when a higher EP-TOMS instrument degradation occurred. Despite its low magnitude, the EP-TOMS-Brewer relative differences depend on the solar zenith angle (SZA), showing a clear seasonal cycle with amplitude between ±2% and ±4%. Conversely, OMI-Brewer relative differences show a constant negative value around -1% with no significant dependence on SZA. No significant dependence on the ground-based to satellite-based differences with respect to the EP-TOMS scene or to the OMI crosstrack position is observed for either satellite retrieval algorithm. Finally, TOC, estimated by the two satellite instruments, have also been compared, showing a good agreement (R2 ~ 0.88). Overall, we conclude that the empirical correction of the EP-TOMS data record provides a reprocessed set of high quality. However, EP-TOMS data after year 2000 should not be used in calculations of global-ozone trending due to remaining errors in the data set and because it is no longer an independent data set.

Intercomparisons of Mobility Size Spectrometers and Condensation Particle Counters in the Frame of the Spanish Atmospheric Observational Aerosol Network

Red Española de DMAs Ambientales (REDMAAS), the Spanish network of environmental differential mobility analyzers (DMAs), currently comprises six research groups involved in the measurement of atmospheric aerosol size distributions by means of DMAs. The aim of this network is to guarantee the good quality and comparability of the routine measurements carried out at each location and in diverse environments across Spain. In order to achieve this objective, one of its main activities is the annual intercomparison of mobility size spectrometers used within the network (five units of scanning mobility particle sizers [SMPS] and one ultrafine particle monitor [UFPM]). Here we report the 2main results obtained during the 2010–2012 campaigns, including a study on particle deposition in dryers used in ambient air sampling systems. In general, all instruments showed good performance with deviations in accepted tolerance. The intercomparisons have been proved to be a useful exercise to detect instrument problems, such as incorrect calibrations. DMA calibration checks were performed with polystyrene latex reference particles. Deviations of less than 1% were observed during the first year, which increased 4.7% during the last campaign. Some differences among the responses of different condensation particle counter (CPC) models were encountered, being mainly connected to the intrinsic characteristics of each counter. The comparison of UFPM with CPCs has given good results. The SMPS intercomparisons, especially for particles above 20 nm, have been within +/−15% tolerance. Regarding particle deposition in dryers used in sampling systems, particle penetration was lower than predicted by the recommended model. This result was probably due to the fact that not all the possible mechanisms were considered in the model. Copyright 2015 American Association for Aerosol Research

Comparison of aerosol size distributions measured at ground level and calculated from inversion of solar radiances

Ground-based sunphotometry measurements can be used to investigate atmospheric aerosol optical properties, such as the volume size distribution, an important parameter in the study of the effect of aerosol on atmospheric processes. Most inversion algorithms assume constant aerosol optical characteristics over the whole air column. In this work we present observational evidence of the limitations of this simplifying assumption in cases where the aerosol vertical structure is highly inhomogeneous. During the field campaign VELETA 2002, carried out in Granada (Spain), a quite complete characterization of the atmospheric aerosol was obtained by simultaneously measuring the columnar aerosol characteristics, by means of CIMEL C318 sun-tracking photometers, the size-segregated near-surface aerosol mass concentration by a GRIMM 1108 dust monitor and the aerosol vertical profiles by a lidar system. During the last days of the campaign, a dust-rich air mass from the Sahara reached the site, producing a multilayered structure on the aerosol vertical profile. The ground level size distributions can be compared with the columnar ones using retrieved scale height values from a lidar extinction coefficient profiles, corresponding to the altitude where the integrated extinction is equal to 1-e-1 of the AOD. Comparisons of the column-integrated and the modified ground-level aerosol size distributions show a good agreement in the days previous to the arrival of the Saharan intrusion, when the aerosols are homogeneously distributed in a well-mixed boundary layer. But, when the vertical homogeneity is reduced due to elevated layers containing desert dust, the column properties clearly deviates from the surface properties. This indicates the importance of verifying the vertical distribution of aerosol in order to correctly relate column and ground-level optical properties.

Assessment on the Ozone Air Pollution in a Medium Metropolitan Area: Seville (Spain)

Problems caused by the air pollution which are generated mainly in metropolitan areas and industrial complexes, become in the major challenges for the current society. The air pollution has its origin in the chemical species emission into the atmosphere which may be harmful for human health (Lin, et al., 2008; Doherty et al., 2009), vegetation and ecosystems (Cape, 2008). The pollutants in the atmosphere can be classified in primary, directly emitted to the atmosphere, or secondary, formed in the atmosphere from chemical or photochemical reactions. Nowadays, the main air pollution problems are originated by secondary chemical species, as particles and surface ozone (Kumar et al., 2010; Lefohn et al., 2010). In Europe, there are several Directives to protect air quality, as the Directive 2008 which defines the new threshold for different pollutants. Generally, the highest concentrations of secondary species are registered in areas far away from the emissions sources, as suburban and rural areas. Nevertheless, there are urban areas that due to both meteorological and emissions conditions can suffer high levels of secondary substances (Papanastasiou and Melas, 2009; Alvim-Ferraz et al., 2006). In many countries there are air quality networks which measure concentrations both primary (NO, CO, SO2) and secondary pollutants and provide air quality information in real-time. However, in spite of the elevated economic cost of these networks, it is usual that the collected data are only used to determinate if a pollutant exceed the legal threshold according to the current Directive. Nevertheless, with the information obtained in the air quality networks is possible to carry out studies in order to improve the understanding of the atmospheric pollution and to help in the definition of plans and control strategies to the air quality. The work presented in this chapter is linked with a secondary pollutant, surface ozone, using data from an air quality network in a sensible region suitable to photochemical pollution problems. The study has been carried out in the Seville metropolitan area (low

Aerosol optical depth derived from lidar measurements during VELETA-2002 campaign

We present measurements of the vertical structure of the aerosol extinction coefficient in the lower troposphere, up to five kilometers. Lidar profiles were collected at Armilla (680 m asl) and Pitres (1252 m asl) during the VELETA-2002 campaign, organized to analyze the effect of altitude and aerosols on ground-level UV spectral irradiance. Single-wavelength lidar signals are inverted to derive vertically resolved aerosol extinction coefficient and integrated to provide aerosol optical depth (AOD) at 532 nm. These results are compared with measurements of the aerosol optical depth at the same wavelength provided by Licor LI-1800 spectroradiometers located at several altitudes. Lidar traces show that most of the aerosol loading is present in the first 2.5 km layer before a high-dust Saharan air mass overflew the site. On the 17th of July evening, an elevated aerosol layer was detected between 2.5 and 3.5 km and during the following three days the aerosol vertical profile of the lower atmosphere showed Sahara dust layers, producing relatively high values for the optical depth.