Study of the influence of different organic pollutants on Cu accumulation by Halimione portulacoides

The influence of each of four organic pollutants selected from among those commonly found in coastal areas, 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE), monobutyltin (MBT), Triton X-100 and polycyclic aromatic hydrocarbons (PAHs), on Cu accumulation by Halimione portulacoides was investigated. Experiments were carried out in a laboratory setting, either in hydroponics (sediment elutriate) or in a salt marsh sediment (Cávado River, NW Portugal) soaked in elutriate. Groups of H. portulacoides were exposed to media for 6 days spiked with 10 mg/L Cu(II) and with one of the selected pollutants, at an environmentally realistic concentration. DDE and MBT did not cause any major change on Cu accumulation by H. portulacoides, whereas PAHs slightly increased accumulation only in hydroponics i.e. in the absence of sediment. On the other hand, the non-ionic surfactant Triton X-100 markedly favoured Cu accumulation on plant roots both in the presence and absence of sediment. The addition of DDE, MBT and Triton X-100 also favoured Cu solubility from sediments. Therefore, the simultaneous presence of pollutants from different nature (inorganic and organic) in the estuarine environment may result in a composition of water column, pore water, sediment or biota different of that expected considering the effect of each individual pollutant.     

Can PAHs influence Cu accumulation by salt marsh plants?

The presence of polycyclic aromatic hydrocarbons (PAHs) may change the mechanisms of metal uptake, thus influencing kinetics and extent of metal phytoextraction. Studies on the subject are scarce, particularly for salt marsh plants. The aim of this work was to investigate the effect of PAHs on the uptake of Cu by Halimione portulacoides, a plant commonly found in salt marshes. Experiments were carried out in the laboratory, either in hydroponics (sediment elutriate) or in sediment soaked in elutriate, which were prepared with sediment and water from a salt marsh of the Cavado river estuary (NW Portugal). Groups of H. portulacoides (grown in a greenhouse) were exposed to those media during six days. Cu(2+) (as Cu(NO(3))(2)), 10(2) and 10(4)mugl(-1), was added to the media as well as 1.6mugl(-1) of the sixteen EPA priority PAHs (0.1mugl(-1) of each PAHs). Cu was assayed in solutions, sediments and different plant tissues before and after experiments. After exposure, photosynthetic efficiency and levels of chlorophylls were also measured, indicating that plant stress indicators were identical in all plants independently of the media to which the plants were exposed. PAHs influenced both the soluble Cu fraction and Cu uptake by plants. The amounts of metal accumulated in both roots and stems were significantly higher when the 10(4)mugl(-1) of Cu enriched elutriate was amended with PAHs. Thus, results suggest that PAHs may modify Cu solubility, the Cu sorption by plants and/or the passive penetration of Cu into the root cells. Therefore, the combined effects of different types of pollutants should be taken in consideration when studying the remediation potential of plants, namely in terms of phytoextraction.     

Granulometric selectivity in Liza ramado and potential contamination resulting from heavy metal load in feeding areas

The stomach contents of thin-lipped grey mullets Liza ramado were analysed in terms of granulometric composition and compared to the sediment of potential feeding areas in the Tagus estuary. Total organic matter (TOM) content and heavy metal content were determined in the surface sediment of three areas and eight trace elements were quantified: Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn. The three sampled areas did not differ in TOM; and the heavy metal content was below Effects Range-Low level for most elements. The mean observed concentrations were present in the following sequence: Zn > Pb > Cr > Cu ≈ Ni > Co > Cd > Hg. Stomach contents granulometric composition provided information about the feeding selectivity of the mullets. Sediment fractions with particle size between 20 and 50 μm are preferred, independently of the fishes' length. Smaller standard length (SL) fishes have a higher positive selection of fine grained sediments than those with a larger SL. Finer fractions usually have higher concentration of heavy metals, which makes younger specimens of the thin-lipped grey mullet potentially more exposed to heavy metal load in the estuary. Metal concentration was not independent from the sampling point, presenting higher values near the margins and the estuary tidal drainage system. This means that during the first period of each tidal cycle, the mullets will feed first on the most contaminated areas, as a consequence of their movement following the rising tide to feed on previously exposed areas.     

An analysis of the spectrophotometric and photometric observations of comets 1967II, 1968I, 1968V,and 1968VI

Emission fluxes of CN, C₂ and C₃ carbon-bearing molecular species observed in the coma of comets Rudnicki (1967II), Ikeya-Seki (1968I), Whitaker-Thomas (1968V), and Honda (1968VI) are analysed in the framework of Haser model. CN, C₃ and C₃ production rates are determined using recently derived fluorescence efficiencies. The dependence of CN, C₂ and C₃ production rates on the heliocentric distance and the possible correlations among these radicals is studied. It is shown that comets Ikeya-Seki (1968I) and Honda (1968VI) have the same mean color indices (B-V) and (U-B).     

Haser model CN,C2 and C3 production rates in some comets

Emission fluxes of CN, C₂ and C₃ species observed in the coma of some comets are analysed in the framework of Haser model. CN, C₂ and C₃ production rates are determined using recently derived fluorescence efficiencies and dependence of CN, C₂ and C₃ production rates on the heliocentric distance is studied. Evidence for a burst type activity around January 15, 1974 in the post-perihelion period of comet Kohoutek (1973f) is observed.     

3-D electromagnetic imaging of a Palaeozoic plate-tectonic boundary segment in SW Iberian Variscides (S Alentejo, Portugal)

In SW Iberian Variscides, the boundary between the South Portuguese Zone (SPZ) and the Ossa Morena Zone (OMZ) corresponds to a major tectonic suture that includes the Beja Acebuches Ophiolite Complex (BAOC) and the Pulo do Lobo Antiform Terrane (PLAT). Three sub-parallel and approximately equidistant MT profiles were performed, covering a critical area of this Palaeozoic plate-tectonic boundary in Portugal; the profiles, running roughly along an NE–SW direction, are sub-perpendicular to the main Variscan tectonic features. Results of the three-dimensional (3-D) modelling of MT data allow to generate, for the first time, a 3-D electromagnetic imaging of the OMZ–SPZ boundary, which reveals different conductive and resistive domains that display morphological variations in depth and are intersected by two major sub-vertical corridors; these corridors coincide roughly with the NE–SW, Messejana strike–slip fault zone and with the WNW–ESE, Ferreira–Ficalho thrust fault zone. The distribution of the shallow resistive domains is consistent with the lithological and structural features observed and mapped, integrating the expected electrical features produced by igneous intrusions and metamorphic sequences of variable nature and age. The development in depth of these resistive domains suggests that: (1) a significant vertical displacement along an early tectonic structure, subsequently re-taken by the Messejana fault-zone in Late-Variscan times, has to be considered to explain differences in deepness of the base of the Precambrian–Cambrian metamorphic pile; (2) hidden, syn- to late-collision igneous bodies intrude the meta-sedimentary sequences of PLAT; (3) the roots of BAOC are inferred from 12 km depth onwards, forming a moderate resistive band located between two middle-crust conductive layers extended to the north (in OMZ) and to the south (in SPZ). These conductive layers overlap the Iberian Reflective Body (evidenced by the available seismic reflection data) and are interpreted as part of an important middle-crust décollement developed immediately above or coinciding with the top of a graphite-bearing granulitic basement.     

Volcanic-sedimentary features in the Serra Geral Fm., Paraná Basin,southern Brazil: Examples of dynamic lava-sediment interactions in an arid setting

The formation of volcanic–sedimentary interaction features in extreme arid environments is not a commonly described process. Specifically the occurrence of dynamically mixed sediments and juvenile igneous clasts as peperites, for water has been considered one major important factor in the processes of magma dismantling and mingling with unconsolidated sediment to form such deposits. The study area, located in south Brazil, shows a sequence of lava flows and intertrapic sandstone layers from the Paraná Basin, associated with the formation of clastic dykes, flow striations, peperite and ‘peperite-like’ breccias. Four processes are suggested for the genesis of the peperites: (a) fragmentation of the flow front and base; (b) sand injection; (c) dune collapse; (d) magma cascade downhill. The continued flow of a lava, while its outer crust is already cooling, causes it to break, especially in the front and base, fragments falling in the sand and getting mixed with it, generating the flow front ‘peperite-like’ breccia. The weight of the lava flow associated to shear stress at the base cause sand to be injected inwards the flow, forming injection clastic dykes in the cooled parts and injection peperite in the more plastic portions. The lava flow may partially erode the dune, causing the dune to collapse and forming the collapse ‘peperite-like’ breccia. The shear stress at the base of a flowing lava striates the unconsolidated sand, forming the flow striations. The sand that migrates over a cooled, jointed lava flow may get caught in the cavities and joints, forming the filling clastic dykes. These deposits are analogous to those found in the Etendeka, NW Namibia, and show that sediment–lava interactions in arid settings are widespread throughout the Paraná-Etendeka province during the onset of flood volcanism.     

Hydrogeological investigation in Santiago Island (Cabo Verde) using magnetotellurics and VLF methods

A geoelectromagnetic research was carried out in the Santa Cruz region (Santiago Island, Cabo Verde) during June 2004. The survey comprised MT soundings and VLF profiles. The main purpose of the MT profile, carried out across three important valleys associated with freshwater aquifers, was to study the tectonic structures correlated to seawater infiltration. The VLF method was used inside of the valleys for investigating shallow structures related to the aquifer contamination by seawater.Numerical modelling shows that the ocean effect is not important for MT data collected at periods shorter than 1 s. The MT data were inverted using a two-dimensional approach, to obtain the sub-superficial electrical conductivity distribution. The VLF data were processed applying the Karous–Hjelt filters to obtain the equivalent current distribution and inverted using 2-D approach. The results obtained in one of the most important valleys show anomalous current concentration/low resistivity (<20 Ω m) areas at depths greater than 40 m that may correspond to an increase in seawater content.The MT data modelling show that the deep zones beneath the valley are strongly fractured representing good pathways for seawater circulation. The depth of the conductive zones increases from south to north, suggesting a northward decreasing of the seawater infiltration effect. This observation correlates very well with in situ geochemical observations.     

A bin-microphysics cloud model with high-order, positive-definite advection

An axisymmetric, anelastic model of a convective cloud is described. The model comprises prognostic equations for the azimuthal vorticity, the perturbation potential temperature, the perturbation water vapor mixing ratio, 44 categories of cloud condensation nuclei, and 100 categories of liquid-phase hydrometeors. Results from a control simulation show that the model is capable to reproduce realistically the life cycle of a convective cloud including the production of warm rain.A discussion of the role of advection in bin-microphysics models is presented and sensitivity tests were performed regarding the order of advection. The results show that, although the global characteristics of all simulated clouds were similar, significant differences occur with respect to their microstructure, particularly close to the cloud edges, when the order of the advective scheme changes. The conclusion is that intermediate-order advection schemes can indeed be used in cloud-resolving simulations, as far only as the gross characteristics of the cloud/cloud system are being investigated, but not poor, low-order schemes. On the other hand, the sensitivity with respect to the advection suggests that the evaluation of cloud phenomena that occur in fine-scales, such as entrainment and certain microphysical and radiational processes, must require the use of accurate, higher-order schemes.     

Assessment of site-effects using acceleration time series. Application to São Sebastião volcanic crater

The Azores archipelago is located at the North America, Eurasia and Africa triple junction and shows seismicity and volcanism typical of an active plate boundary. Terceira Island has been affected by several damaging earthquakes being the 1980 January 1st event (M=7.2) the strongest in Azores during the last century.