How geological origin influences the quality of sand and the environmental impacts of its mining,Bahia state,Northeastern Brazil

The highly increasing demand for sand in Northeastern Brazil, due to governmental economic incentive focused to this region, has necessitated the opening of new extraction mines, generally without adequate environmental control. This study aimed to assess several sand extraction activities in the Recôncavo territory, Bahia state—area with high variability in sedimentary deposits—by evaluating the quality of the sand and the extraction impacts according to the geological basement. The methodology consisted of field research, using satellite images and maps for characterization, application of the environmental and economic impact checklists, and analysis of organic matter, particle size distribution, and salt content in 35 samples from different sand mines. The sands were classified as white sand (from Neossols/weathered aeolian sandstones), brown sand (from mature soils), and river sand. A strong relation between the geological origin and sand type and quality was established. Although the river sand appears to be the best option for extraction with regards to sand quality and low environmental impacts, the white sand derived from Jurassic sandstones is intensively extracted due to easy access, availability of wide deposits, and visual quality and homogeneity. However, the white sand has an inadequate particle distribution due to its poor gradation (aeolian selection of fine particle) and high environmental impacts due to its location in wet tropical ecosystem dominated by the Atlantic forest and the erosion of sandy soils. We demonstrated that the knowledge of lithology is fundamental for mapping new potential sand mines and minimizing the generated impacts.     

Inorganic and methylmercury: do they transfer along a tropical coastal food web?

Methylmercury (MeHg) and inorganic mercury (Hg_inorg) were evaluated in the water of a Brazilian estuary, with two size classes of plankton and seven fish species of different feeding habits. Water partition coefficients (PCs) in microplankton were fourfold higher for MeHg than for Hg_inorg; and water PCs in mesoplankton were 26 times higher for MeHg than Hg_inorg. Difference between microplankton and mesoplankton MeHg bioaccumulation factor (BAF) was higher (0.60 log units) than Hg_inorg BAF (0.24 log units), indicating that trophic transfer of MeHg between planktonic organisms is more efficient than Hg_inorg transference. MeHg concentrations, proportion of mercury as MeHg and its biotransference factors (BTFs) in the microplankton, mesoplankton and fish increased with increasing trophic level while biotic concentrations of Hg_inorg and proportion of mercury as Hg_inorg decreased thus indicating that MeHg was indeed the biomagnified species of mercury. MeHg reflected the vertical trophic guilds distribution, due to the fact that the top predator fish presented the highest concentration (0.77 μg g⁻¹ d.w.), followed by the less voracious species (0.43 μg g⁻¹ d.w.); while planktivorous fish presented the lowest concentrations (0.044 μg g⁻¹ d.w.). Hg_inorg did not present the same behavior. Results suggest that feeding habits and trophic guild are important parameters, influencing biotransference and biomagnification processes.     

On the significance of the climate-dataset time resolution in characterising wind-driven rain and simultaneous wind pressure. Part II: directional analysis

Both semi-empirical methods and CFD simulations use real climate datasets as a basis for determining the building facade exposure to wind-driven rain and simultaneous wind pressure. The time resolution of these datasets and the number of variables considered (commonly rainfall intensity, wind speed and wind direction) determine the required calculation effort and the accuracy of the result. Omitting the wind direction, a former article (Part I of this research) has analysed the effect of this time resolution on two scalar exposure indices obtained by semi-empirical methods: driving rain index (aDRI) and driving-rain wind pressure (DRWP). However, the wind direction during precipitation events also causes significant exposure variations between possible facade orientations. Thus, it is also necessary to clarify the influence of the time resolution of the dataset, on the accuracy of the directional semi-empirical calculation of aDRI and DRWP. To meet this challenge, the article examines 10-min climate records collected between 2001 and 2016 at 6 Spanish locations, uses them to obtain hourly, daily, monthly and annual datasets, and analyses the accuracy of the directional exposure indices associated with each time resolution. The results show that a daily dataset would allow identifying the most exposed orientation with an error less than 45°. However, even the hourly datasets cause errors close to 10% in the exposure values identified on each facade orientation. Finally, adjustment relationships that allow estimating the maximum value of directional exposure from simple scalar indices are obtained.

     

Molecular and biochemical biomarkers responses in the mussel Mytilus edulis collected from Southern Brazil coast

Marine ecosystems are typically subjected to a variety of stressors containing complex xenobiotics mixtures. This study aims to evaluate the responses of molecular and biochemical biomarkers in the mussel Mytilus edulis providing data for environmental monitoring programs development in Southern Brazil. Mussels were collected at a polluted site, near Patos Lagoon outfall, and at a control site. Gills, muscle and mantle samples were used for biomarker determinations. Mussels collected at the polluted site significantly increased superoxide dismutase (SOD) and glutathione S-transferase (GST) activities and decreased catalase (CAT) activity. Moreover, an increase in sod1, gstπ and hsp70 mRNA expression was observed. Overall, biochemical and molecular biomarkers responses were observed, but these responses varied depending on the analyzed tissue. These results indicate possible contaminants effects on organisms and the need for effective environmental monitoring programs in this ecosystem.     

Model sensitivity experiments on data assimilation,downscaling and tides for the representation of the Cape São Tomé Eddies

Ocean Dynamics - The impacts of data assimilation, downscaling, and tidal forcing were investigated with focus on the representation of the Cape São Tomé Eddy (CSTE). Sea level anomaly...     

Seismicity and codaQ values in the eastern Pyrenees: First results from the La Cerdanya seismic network

Seismicity in the La Cerdanya region of the eastern Pyrenees has been accurately mapped for the first time using data from a local seismic network. The majority of earthquakes lies on or near the La Cerdanya fault or secondary faults to the south. Coda magnitudes determined for these earthquakes, using magnitude relations from other regions, range between –0.5 and 2.2. These are, however, presumed to be underdetermined values sinceQ values appear to be very low in the La Cerdanya region. CodaQ values at a frequency of 1.5 Hz range between 17 and 120, the lowest values being obtained for the most seismically active regions. CodaQ values also increase with increasing distance, a result which indicates decreasing seismic attenuation with increasing depth in the crust.     

Plate tectonics and volcanism in the gibraltar arc

Late Tertiary and Quaternary volcanism of southeastern Spain can be fitted in a platetectonics model, taking into account the post-Paleozoic evolution of the stable and semimobile Iberian areas and the new orogenic belts bordering the Mediterranean between Africa and the Iberian Peninsula.The occurrence and distribution of calc-alkaline and potassic volcanism suggest an oceanic crust sinking downwards from the Iberian plate. This active margin is causally related to the convergence and collision of Iberia and Africa during Late Cretaceous—Early Miocene time span.A pre-collision distensive phase is inferred from the stratigraphie and tectonic record between the Triassic and Late Cretaceous, while since the Late Miocene another distensive phase is related to the actualistic features.     

Late Cenozoic sedimentary process and its response to the slip history of the central Altyn Tagh fault,NW China

The ENE-striking Altyn Tagh fault (ATF), extending along the northern edge of the Ti-betan Plateau, is one of the major important strike-slip faults, and has been known as one of the key areas to debate the eastward extrusion and crustral shortening models of the Tibetan Plateau during and after India-Asia collision. This paper mainly presents new evidence of Late Cenozoic sedimentary process to reconstruct the slip history of the ATF during the Late Cenozoic. Field measurements and laboratory analyses of the sedimentary characteristics in the Late Cenozoic basins in the central Altyn Tagh fault suggest that Late Cenozoic sedimentary sequence should be divided into three units according to facies changes. The paleo-topography reconstruction shows that the sedimentarion in these basins was tightly related with the fault, indicating that the ATF has experienced at least three stages of strike slipping in the Late Cenozoic. New geological data from the Late Cenozoic sedimentary basins and the formation of the present Suo’erkuli basin provide evidence for the displacement of the fault. The result shows that the 80–100 km left-lateral strike-slip displacement of the fault has been accumulated in the Late Cenozoic.

     

由卫星磁异常推断西藏高原地壳的磁性特征

根据前人对本区卫星和航空磁异常所作的研究工作，作者经过综合研究所得的结果是：西藏高原地壳中的磁性层在地表以下30km以内，其磁化率平均为.0167SI,相当于I－型花岗岩类的磁化率，在30km以下，地壳显示为无磁性。