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In the present study an integrated ecological risk assessment based on multiple lines of evidence (LOEs) was evaluated in order to better assess the risk from TBT in Dutch harbours and open coastal waters. On the basis of spatial distributions of measured tributyltin (TBT) concentrations in sediments and suspended matter, predictions of the intersex index (ISI) in Littorina littorea and the ecological risk expressed as the Potentially Affected Fraction (PAF) of species were made. The results were compared to actual ISI measurements and presence of L. littorea in the field. The PAF calculated on the basis of TBT levels for open coastal waters ranged from 4.2% to 15.3%; for harbours it ranged from 3.5% to 26.9%. Significant intersex levels were observed only in waters where the risk was calculated above 10% PAF. This study suggests that the absence of L. littorea from some harbours with high ecological risk values can be explained by high TBT concentrations. A call is made for the use of integrated approaches like weight-of-evidence (WOE) to help practitioners improve ecological risk assessment. 相似文献
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Maria Alfredsson Furio Corà John P. Brodholt Steve C. Parker G. David Price 《Physics and Chemistry of Minerals》2005,32(5-6):379-387
Many rheological and transport properties of rocks are determined by the grain boundary structures of their constituent minerals.
These grain boundaries often also hold a high concentration of dopant ions. Here, as a first step towards modelling the transport
and rheological behaviour of the lower mantle, we report the results of lattice static simulations on the surface structures
of Fe2+ and Ca2+-doped orthorhombic MgSiO3-perovskite. For all the surfaces we studied, the energies of the doped structures are lowered, sometimes by more than 1 J/m2, with respect to the pure surfaces. From our calculated crystal morphologies, we predict that the grains become more tabular
as the concentration of Fe2+ ions increases, while under equilibrium conditions the grains are cubic. By calculating the replacement energies of Mg2+ by Fe2+ and Ca2+ ions in the six outermost surface layers, we conclude that these divalent ions would tend to segregate onto the crystal surfaces.
We suggest, therefore, that the grain boundary structure and rheology of MgSiO3-perovskite dominated rocks will be strongly affected by the presence of minor elements in the lower mantle. 相似文献
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A full understanding of the Mio-Pliocene palaeogeographical and palaeoenvironmental changes in the circum-Mediterranean region during the Messinian Salinity Crisis (MSC) is at present hampered by the lack of reliable chronostratigraphic correlations between the Mediterranean and Paratethys regions. Here, we present magnetostratigraphic ages for the Upper Miocene to Pliocene deposits of the southern Carpathian foredeep in Romania. These ages are in good agreement with those recently obtained from the eastern Carpathian foredeep and define a new chronology for the eastern Paratethys. The Meotian/Pontian boundary is not biostratigraphically constrained in our sections, but according to the geological map of the region arrives at ∼5.8 Ma. The Pontian/Dacian boundary is dated at c. 4.8 Ma and the Dacian/Romanian boundary at c. 4.1 Ma. The main part of the MSC (5.96–5.33 Ma) is thus represented by the Pontian Stage, but the observed palaeoenvironmental and biostratigraphic changes in our sections of the eastern Paratethys do not indicate any relation with the dramatic desiccation and reflooding events of the Mediterranean. 相似文献
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Cristina E. Panaiotu Iuliana Vasiliev Cristian G. Panaiotu Wout Krijgsman Cor G. Langereis 《地学学报》2007,19(2):120-126
Provenance analysis of the sediments from foredeep basins is crucial in understanding the contemporaneous orogenic exhumation processes. We report in this paper complex sediment provenance analysis using sandstone petrography and mudstone geochemistry, combined with magnetic susceptibility of the Upper Miocene to Pliocene deposits from Focşani foredeep basin (Romania). Data show a change of source area between 5 and 6 Ma, from an active volcanic arc towards a recycled orogenic belt, concurrent with an important increase of accumulation rate. This change was triggered by exhumation and erosion of the outer nappes from East Carpathians. 相似文献