Macrobenthos and multi-molecular markers as indicators of environmental contamination in a South American port (Mar del Plata,Southwest Atlantic)

We evaluated benthic habitat quality along a presumed contamination gradient in the Mar del Plata port (Southwestern Atlantic) by coupling biological and chemical proxies in a multidisciplinary approach. Organic matter and photosynthetic pigment contents were higher in silty-clay bottoms of the inner port sites. Levels of all fecal steroids decreased from the inner sites to the port inlet. High concentrations of coprostanol in the inner sites seemed to derive from a permanent population of sea lions rather than from sewage outfalls due to coprostanol/epicoprostanol ratio (IV) values <2.5. PAHs levels were also higher in the inner sector, related to both biomass combustion and petroleum combustion associated to local marine traffic. High disturbance and low ecological status were reflected in low benthic diversity and high AMBI values in the inner sites.     

Significant hot and cold events at the Fabra Observatory, Barcelona (NE Spain)

Summary A long series of maximum and minimum daily temperatures recorded at the Fabra Observatory (Barcelona) from 1917 to 1998 has permitted a detailed study of significant hot and cold events, based on the crossing theory and on the Markovian process. The former allows us to obtain statistical distributions of the number of hot and cold events per year, the starting date and the magnitude of an event. The Poisson, the normal and the exponential distributions are the respective models. On the other hand, the Markovian process estimates probabilities for the duration of several hot and cold events above or below different temperature threshold levels. It should be stressed that the threshold levels, which define the significant hot and cold events, are almost coincident with those whose lengths follow a Markovian process. From a more applied point of view, two examples of hot and cold events of high magnitude are shown and their associated synoptic situations discussed. Some other typical synoptic situations leading to relevant hot and cold events in Barcelona and the surrounding areas are also summarised. Received March 1, 2001 Revised July 30, 2001     

U-Pb Saturn: New U-Pb/Pb-Pb Data Reduction Software for LA-ICP-MS

U-Pb Saturn is new freeware for U-Pb LA-ICP-MS data reduction. It has been developed to provide easy interaction with and visualisation of LA-ICP-MS U-Pb datasets, and allows fast and reliable data reduction of hundreds of data-points. Saturn offers dynamic graphic interfaces to quickly view, evaluate, and plot U-Pb and Pb-Pb isotope data. It operates online (or offline), giving the freedom to change parameters and reprocess data at any stage of data acquisition. The main interface allows the user to: (1) choose the best statistics for drift correction, (2) include/exclude offset factors and (3) apply (or not) Pb_c corrections in different modes. Signal intensities are displayed in a separate graphic interface that allows users to interact with the time-resolved signal of individual spot analyses. All graphic windows are interactive; any modification to data treatment (e.g., inclusion or exclusion of analyses of reference material, or modification of the time-resolved signal windows) is instantaneously updated on the data tables. Saturn is particularly attractive for beginners in LA-ICP-MS U-Pb geochronology as it is non-commercial, easy to install, and very interactive. Coding information and a version of the software can be accessed at http://www.air.ufop.br .     

Joint inversion of travel times and waveforms by means of annealing algorithms. Application to a seismic refraction experiment

An algorithm of annealing is applied to a joint inversion of travel times and waveforms belonging to a synthetically generated seismic refraction experiment. The medium (crust and upper mantle) is modelled by a set of plane stratified layers and a halfspace. The obtained structure (elastic parameters and depth of layers) shows that, in spite of contaminating seismic noise and poor knowledge of the seismic source, annealing methods are a good tool in these kinds of inversion problems. We think that many characteristics of the annealing process described here could be used with real data and more sophisticated media for the crust and upper mantle of the earth than the present example.     

European dry spell length distributions, years 1951–2000

Daily precipitation records of 267 European rain gauges are considered to obtain dry spell length (DSL) series along the second half of the twentieth century. A dry spell consists of consecutive days with daily rain amount below a given threshold, R ₀. Four DSL series are obtained for R ₀ values equal to 0.1, 1.0, 5.0, and 10.0 mm/day, and their empirical distributions are properly fitted to different statistical models: Pearson type III (PE3), Weibull (WEI), generalised Pareto, (GPA) and lognormal distributions. The parameters of every model are estimated by L-moments, and the goodness of fit is assessed by quantifying discrepancies between empirical and theoretical distributions in the L-skewness–kurtosis diagrams. The most common best-fitting model is PE3, especially for 0.1 and 1.0 mm/day. Nevertheless, a few stations in southern Europe are better modelled by the WEI distribution. For 5.0 and 10.0 mm/day, the spatial distribution of the best-fitting model is more heterogeneous than for the lowest thresholds. While PE3 is still the preferred model for Western Europe, some DSL series are better fitted to WEI or GPA models. Maps of DSL average and standard deviation and expected lengths for return periods of 2, 5, 10, 25, and 50 years show some common features. Whereas for thresholds of 0.1 and 1.0 mm/day, a N–S gradient is detected, especially in Mediterranean areas; for 5.0 and 10.0 mm/day, a NW–SE gradient is observed in the Iberian Peninsula and a SW–NE gradient in the Scandinavian Peninsula. Then, the vicinity to Atlantic and Arctic Oceans and the Mediterranean Sea, as well as orographic features, are more determining factors than the latitude in patterns associated with the highest R ₀ thresholds. Finally, a regional frequency analysis based on a clustering algorithm is attempted for the four thresholds R ₀, with the PE3 model as the parent distribution for the largest clusters.     

Stress–Strain Analysis of Buckling Failure in Phyllite Slopes

Buckling failure occurs in the open pit mines in the Quadrilátero Ferrífero of the State of Minas Gerais, Brazil. In this study, this failure mechanism is evaluated through stress–strain analysis, using the finite element software named Phase². Many representative hypothetical models of the slopes were created in order to reproduce the conditions in open pit mines, like their geometry and foliated joints with kinematic conditions for buckling failure. Elastic and plastic simulations have been done. Strength and deformability parameters, such as discontinuity stiffness and cohesion, as well as the in situ stress field, are analyzed in order to understand their influence in the buckling failure mechanism in the global open pit mine slopes excavated in phyllites. As studies about this problem are extremely rare, the present research brings important contributions to establish the basic conditions for this kind of failure.     

Lateral variations of attenuation coefficients, group and phase velocities of rayleigh waves in Europe

Rayleigh wave group and phase velocities and attenuation coefficients are investigated in the 15–60-s period range for earthquakes occurring in the European area and registered at European stations. Observed group and phase velocities show clear differences in the period range 20–40 s, whereas attenuation coefficients are differentiated from 45 s to larger periods. From the shape of dispersion and attenuation curves, two broad zones have been isolated and designated as Western Europe and Southeastern Europe. Although some scatter is present, specially for attenuation, the data suggest that in general the shear velocity and Q_β values are higher for Southeastern Europe than for Western Europe. For Southeastern Europe there is a channel of low velocity and low Q_β, apparently correlated, located at the lower crust: in both regions there is a channel of low velocity and low Q_β values located at the uppermost mantle. In each case there also exists a channel of high Q_β values located at the lower crust but at slightly different depths.