CH₄/N₂/H₂ spark hydrophilic tholins: A systematic approach to the characterization of tholins     

Marta Ruiz-Bermejo  César Menor-Salván  Susana Osuna-Esteban  Sabino Veintemillas-Verdaguer 《Icarus》2008,198(1):232-241

Tholins are complex organic materials produced by irradiation of several carbon and nitrogen rich atmospheres. They could have played a key role in the origin of life on Earth because their ability to release important bioorganics, which are nowadays present in proteins, nucleic-acid bases and other important biostructures. Usually, the yield of these compounds is higher after acid hydrolysis, however little is known about the structure and chemical composition of the tholins. In this work, we propose the use of different spectroscopic and separation techniques, which are not usually applied in this field, in order to obtain complete information about the tholin structure and behavior. Two different simulation experiments of prebiotic synthesis were carried out in CH₄/N₂/H₂ atmosphere out from spark discharge activation of aqueous aerosols and liquid water, respectively. In both cases, a hydrophilic tholin and a hydrophobic tholin were obtained. Herein, we report the application of this methodology to our hydrophilic tholins and we review, briefly, some astrobiological aspects related to these complex substances.  相似文献   

Population dynamics and production of the seagrass Zostera noltii in colonizing versus established meadows     

Susana Cabaço  Rui Santos  Martin Sprung 《Marine Ecology》2012,33(3):280-289

The dynamics of the seagrass Zostera noltii in established and colonizing meadows were assessed in Ria Formosa lagoon, Southern Portugal. Shoot weight, above:belowground biomass ratio, flowering shoot density, meadow production, and biomass–density relationships were investigated. Results indicate that the species population dynamics differ clearly in different development stages of the meadows. The overall mean of flowering shoot density was five times higher in the colonizing (83 flowering shoots m⁻²) than in the established meadow (16 flowering shoots m⁻²), revealing a greater contribution of sexual reproduction during the species colonization process. The temporal variation of the biomass–density relationship in the colonizing meadow showed a cyclic seasonal trajectory, a wider range of data, and a simultaneous peak of biomass and density, suggesting no space limitations constraining the internal packing of shoots during the growing season. In the established meadow, density peaked before biomass in agreement to the dominant role of the clonal architecture of seagrasses in the configuration of closed meadows, suggesting the occurrence of self-thinning and/or regulation of ramet formation. Slope of the biomass–density relationships was similar in the established and colonizing meadows, generally suggesting similar nutritional conditions, regardless of their muddy and sandy sediments. Plants of the colonizing meadow invest mainly on the belowground fraction (above:belowground biomass ratio <1), as meadow expansion is mainly controlled by the elongation of horizontal rhizomes. The annual total production (1163 g C m⁻² year⁻¹) and the biomass turnover (34.8 year⁻¹) were also higher in this meadow, corroborating the high investment of the species during the meadow expansion. The faster biomass turnover of the colonizing meadow implies a more limited capacity to accumulate biomass, indicating a greater exportation of organic carbon and nutrients to the coastal area. The different biomass turnover rates suggest different trophic and structural roles of Z. noltii communities in established and colonizing meadows.  相似文献   

Peroxisomal proteomics: Biomonitoring in mussels after the Prestige’s oil spill     

Itxaso Apraiz  Miren P. Cajaraville  Susana Cristobal 《Marine pollution bulletin》2009,(12):1815-1826

Peroxisomal proteomics was applied to assess possible biological effects after the Prestige’s oil spill. Mussels were sampled in July 2004 and 2005 in four stations in the NW (closest to the spill) and NE coasts of the Iberian Peninsula. Principal components analysis (PCA) suggested differences in protein expression among stations and sampling years. Several proteins were putatively identified by mass spectrometry and immunolocalization. PC1 separated the NW stations in 2004 from the rest of the stations and sampling years mainly due to up-regulation of peroxisomal β-oxidation proteins and PMP70. PC3 separated the NE stations, based on up-regulation of the antioxidant enzyme catalase in 2004 compared to 2005. PC4 separated the stations in the NE and the NW. This work shows that environmental proteomics, together with multivariate data analysis, could provide information to interpret the effects of oil spills at cellular level in mussels.  相似文献   

Products and Mechanism of the NO<Subscript>3</Subscript> Reaction with Thiophene     

B.?Caba?asEmail author  M.?T.?Baeza  P.?Martín  S.?Salgado  F.?Villanueva  E.?Monedero  K.?Wirtz 《Journal of Atmospheric Chemistry》2005,51(3):317-335

Products of the gas-phase reaction of the NO₃ radical with thiophene have been investigated using different experimental systems. On the one hand, experiments have been conducted in our laboratory using two different methods, a Teflon static reactor coupled to a gas chromatograph combined with mass-spectrometry (GC-MS) and a discharge flow tube with direct MS spectroscopic detection. A qualitative analysis in these cases indicates that possible products for the reaction of thiophene+NO₃ at room temperature include: sulphur dioxide, acetic and formic acids, a short-chain aldehyde, 2-nitrothiophene and 3-nitrothiophene. On the other hand, quantitative experiments have been performed in the European Photoreactor (EUPHORE) in Valencia, Spain. In this case, the major products were: HNO₃ (≈80%), nitrothiophenes (≈30%), SO₂ (≈20%), propanal (3%) and a fraction of particles (≈10%). The results obtained indicate that at least 70% of the reaction of NO₃ with thiophene proceeds by an H-abstraction process at room temperature. The mechanism of the reaction studied is proposed on the basis of experimental results.  相似文献   

Long-term decline of the populations of Fucales (Cystoseira spp. and Sargassum spp.) in the Albères coast (France, North-western Mediterranean)     

Thibaut T  Pinedo S  Torras X  Ballesteros E 《Marine pollution bulletin》2005,50(12):1472-1489

Only five of fourteen species of Fucales reported at the end of the XIXth century are currently present in the Albères Coast (France, NW Mediterranean). According to historical data there has been a steady decrease of all the populations since the 1940s. Seven taxa now extinct (Cystoseira crinita, Cystoseira barbata, Cystoseira foeniculacea f. tenuiramosa, Cystoseira spinosa, Cystoseira spinosa var. compressa, Sargassum hornschuchii and Sargassum vulgare) were considered frequent and some of them were the dominant and engineering species in several phytobenthic assemblages. Moreover, only one of the five species left, shows no signs of regression (Cystoseira compressa), two are considered as rare (Cystoseira caespitosa, Cystoseira zosteroides), and one is very rare (Cystoseira elegans). Cystoseira mediterranea, a species that was reported to make a continuous belt along the shores of the Albères coast, has almost disappeared from some areas. Overgrazing by sea urchins, outcompetition by mussels, habitat destruction, scientific research sampling and, probably, human trampling and chemical pollution are to be blamed for the decline of populations thriving in shallow waters. Deep-water species have been affected by an increase in water turbidity and, probably, chemical pollution and direct plant destruction attributed to net fishing. If degradation of the environmental conditions continues, the remaining Cystoseira species will face a most unwelcome prospect. Even after the removal of the causes that led to its die-off, natural restoration of extinct species seems not to be possible because the decline has also affected populations from nearby areas and zygotes are unable to disperse over long distances. Urgent management actions have to be designed in order to improve the current situation of the populations of Fucales in the Albères coast.  相似文献   

Implications of sea-level rise for overwash enhancement at South Portugal     

Ferreira  Óscar  Kupfer  Sunna  Costas  Susana 《Natural Hazards》2021,109(3):2221-2239

Overwash is one of the most prominent hazards affecting coastal zones, and the associated consequences are expected to increase because of both sea-level rise and intensification of coastal occupation. This study used a 23-year data set of wave heights and tide-surge levels to define return periods of overwash potential for current and future sea-level conditions, namely 2055 and 2100, at two sites from South Portugal. A relevant intensification of both frequency and magnitude of the overwash is expected to occur by mid-century if adaptation measures are not taken and further aggravated by 2100. Current overwash levels with a return period of 100-years can reach a return period lower than 20-years by 2055 and 10-years by 2100. However, these values are rather variable from site to site, highlighting the urgency to develop detailed local studies to identify climate change impacts along coastal sectors, based on validated equations and long-term time series. These could be easily carried by replicating and adapting the here proposed methodology to sandy coasts worldwide. Understating the impact that climate change (namely sea-level rise) may have at the local level is key to contribute to effective management plans that include adaptation measures to minimize risks associated with coastal floods.

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Temporal evolution of lead isotope ratios in sediments of the Central Portuguese Margin: A fingerprint of human activities     

Mário Mil-Homens  Miguel Caetano  Ana M. Costa  Susana Lebreiro  Thomas Richter  Henko de Stigter  Maria A. Trancoso  Pedro Brito 《Marine pollution bulletin》2013

Stable Pb isotope ratios (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb), ²¹⁰Pb, Pb, Al, Ca, Fe, Mn and Si concentrations were measured in 7 sediment cores from the west coast of the Iberian Peninsula to assess the Pb contamination throughout the last 200 years. Independently of their locations, all cores are characterized by increasing Pb/Al rends not related to grain-size changes. Conversely, decreasing trends of ²⁰⁶Pb/²⁰⁷Pb were found towards the present. This tendency suggest a change in Pb sources reflecting an increased proportion derived from anthropogenic activities. The highest anthropogenic Pb inventories for sediments younger than 1950s were found in the two shallowest cores of Cascais and Lisboa submarine canyons, reflecting the proximity of the Tagus estuary. Lead isotope signatures also help demonstrate that sediments contaminated with Pb are not constrained to estuarine–coastal areas and upper parts of submarine canyons, but are also to transferred to a lesser extent to deeper parts of the Portuguese Margin.  相似文献   

Assessing rheological properties of fluid mud samples through tuning fork data     

Fonseca  Diego Luiz  Marroig  Patrícia Cunha  Carneiro  Juliane Castro  Gallo  Marcos Nicolás  Vinzón  Susana Beatriz 《Ocean Dynamics》2019,69(1):51-57

Ocean Dynamics - At the nautical bottom approach, part of the fluid mud layers can be included in the available depth if they present favorable rheology. As it is difficult to perform in situ...  相似文献