Heavy Metal Accumulation in the Lichen Evernia prunastri Transplanted at Urban, Rural and Industrial Sites in Central Italy     

Marcelo Enrique Conti  Mabel Tudino  Jorge Stripeikis  Gaetano Cecchetti 《Journal of Atmospheric Chemistry》2004,49(1-3):83-94

The lichen Evernia prunastri has been employed for biomonitoring the atmospheric deposition of heavy metals at urban, rural and industrial sites in Central Italy. Lichen samples have been collected in a control site 1500 m a. s. l. (Parco Nazionale dAbruzzo, Central Italy) and subsequently transplanted at urban site (Cassino city center), at rural location 7 km away from Cassino (S. Elia Fiumerapido) and at industrial location (Piedimonte S. Germano) surrounding an automobile factory. Once defined the surface of impact relevant to this work, the lichen samples were transplanted at the four cardinal points of each site. Studies of bioaccumulation of Pb, Cd, Cr, Cu and Zn in lichen samples were performed five times at regular intervals between November 2000–December 2001. Microwave digestion of the samples and graphite furnace atomic absorption spectrometry were employed for the heavy metal determinations. Suitable certified reference materials (CRM) were used for validation of the analytical methodology. Results showed the ability of Evernia prunastri to accumulate the heavy metals under study. As expected, the area chosen as control site showed significantly (Friedman test, cluster analysis) lower impact in comparison to the other sites and the rural site showed smaller impact than the urban and the industrial sites.  相似文献   

Brans-Dicke Quantum Cosmology     

Enrique Guzmán 《Astrophysics and Space Science》1997,253(1):7-12

By solving a Wheeler-De Witt ‘extended’ equation in the Brans-Dicke theory, we have found that the probability distribution predicts: i) An initial value for the Brans-Dicke scalar field φ ∼ ρ^1/2_VAC in the beginning of the inflation, where ρ_VAC is the vacuum density energy (this gives a planck mass ∼ ρ^1/4_VAC) ii) Large values for the Brans-Dicke parameter w. On the other hand it is shown that by taking into account the dynamical behaviour of φ and the matter scalar field σ we can formulate a ‘creation boundary condition’ where in the ‘beginning’ of the Universe (R =0, ‘nothing’ for some authors) we have a dynamical σ already ‘created’. This could be the energetic mechanism which makes Universe tunnels the potential barrier to evolve classically after. Besides we have found the possibility of a cosmological uncertainty principle. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

210Pb in a tropical coastal lagoon sediment core     

F. Páez-Osuna  Enrique F. Mandelli 《Estuarine, Coastal and Shelf Science》1985,20(3):367-374

Excess ²¹⁰Pb in a core from a Mexican Coastal Lagoon, which has no connection with the sea shows a small but measurable decay over the length of the core, when different approaches were compared (excess and corrected ²¹⁰Pb activity with depth, total and inorganic cumulative weights) significant differences in the values for the sedimentation rate are obtained. The best coefficient correlation was calculated when corrected ²¹⁰Pb activity for the uneven distribution of organic matter and cumulative inorganic weight is considered ($\text{ω}\text{= 0·93 cm yr}{}^{\mathrm{?1}}$, R = ?0·86; ω = 0·51 cm yr^?1 for the top 13 cm, R = ?0·90 and 1·52 cm yr^?1 for the interval 14–46 with R = ?0·96).Time frames in the sedimentary column were in agreement between the ²¹⁰Pb calculated time and the appearance of shells fragments probably associated with the disturbances caused by the 1961 hurricane Tara.The surface accumulation rate is equivalent to a mean deposition of 262·5 g m^?2 yr^?1 or organic matter which is minor but comparable to some salt marshes of United States.  相似文献   

Analysis of leaky sheetpile by Summary Representation     

Gabor M. Karadi  Enrique De Miguel  Raymond J. Krizek 《国际地质力学数值与分析法杂志》1980,4(3):199-213

A numerical technique called Summary Representation was used to solve the problem of seepage through a leaky sheetpile; this particular method was selected owing to its accuracy and computational speed. Seepage parameters were evaluated quantitatively and the influence of the leakiness of sheetpiles in a porous medium underlain by an impervious horizontal stratum was determined. The case of a single sheetpile was first considered, and the effect of the depth of penetration and coefficient of leakiness on the total rate of flow and on the values of the exit gradient was analysed. Next, the flow under an impervious dam was considered to assess the accuracy of the method. Finally, the case of seepage under a dam with leaky sheetpiles at both ends was studied, including the effect of the leaky sheetpiles on the uplift pressure acting along the foundation of the dam. Patterns of seepage through the flow line deformation that is caused by the leakiness of the sheetpiles.  相似文献   

Seismic activity along the central america volcanic arc: is it related to subduction of the Cocos plate?     

Marco Guzmn-Speziale  Carlos Valds-Gonzlez  Enrique Molina  Juan Martín Gmez 《Tectonophysics》2005,400(1-4):241-254

We determine seismic strain rate of tectonic earthquakes along the Central America Volcanic Arc. We then compare this result to those obtained from earthquakes related to the convergence of the Cocos and Caribbean plates and to earthquakes in the back-arc region of northern Central America.

The seismic strain-rate tensor for shallow-focus earthquakes along the Central America volcanic arc since 1700, has a compressive eigenvector with a magnitude of 0.7 × 10⁻⁸ year⁻¹, and oriented in a 357° azimuth. The extensive eigenvector is oriented in a 86° azimuth, with a magnitude of 0.82 × 10⁻⁸ year⁻¹. When only Centroid Moment-tensor solutions (CMT) are considered, the respective eigenvectors are 1.2 × 10⁻⁸ year⁻¹ and 1.0 × 10⁻⁸ year⁻¹.

The compressive eigenvector from the seismic strain-rate tensor for earthquakes along the Cocos-Caribbean convergent margin is 2.0 × 10⁻⁸ year⁻¹, plunging at 25°, and oriented in a 29° azimuth. Its magnitude and direction are similar to those of the compressive eigenvector for earthquakes along the volcanic arc. The extensive eigenvector along the convergent margin, on the other hand, has a large vertical component. The compressive and extensive eigevenvectors are 4.9 × 10⁻⁸ year⁻¹ and 4.6 × 10⁻⁸ year⁻¹, using only CMTs as the database.

Earthquakes along the grabens of northern Central America yield a seismic strain-rate tensor whose extensive eigenvector has a magnitude of 2.4 × 10⁻⁸ year⁻¹, oriented in a 109° azimuth. Magnitude and direction are similar to those of the extensive eigenvector for earthquakes along the volcanic arc. The compressive eigenvector along the grabens is practically vertical.

Similarities in magnitudes and directions for compressive and extensive eigenvectors suggest to us that the strain field along the Central America volcanic arc is the result of compression along the convergent Cocos-Caribbean margin, and extension in the back-arc region, along the grabens of northern Central America. This field is resolved as strike-slip faulting along the arc.  相似文献   

Analysis of the mobilization of solid loads and heavy metals in runoff waters from granite quarries     

Enrique Peña González  Joaquín Suárez López  Jordi Delgado Martín  Alfredo Jácome Burgos  Jerónimo Puertas Agudo 《Environmental Geology》2006,50(6):823-834

The cutting operations of dimension stone at quarries produce a large amount of fines that, in turn, cause a negative environmental impact over local surface waters. This article presents a detailed analysis of the mobilized contamination associated with runoff waters in a large granite quarry (～200 ha) which is located in Porriño (Galicia, NW Spain), the most important production centre of dimension stone in Spain. There, an intensive monitoring survey was developed in order to characterize the hydrology of the system as well as the release and transport of pollutants. This was accomplished by means of different control sections for the flow and by the collection of 52 random water samples. Automatic samplers were also used to collect 192 water samples associated with runoff generated by significant rain events. For each of the samples collected, a wide battery of analytic determinations was performed, including solid loads, turbidity, organic pollution, nutrient and selected metals. Upon careful examination it has been possible to obtain different parameters related to the contamination control, like the “event mean concentration” (EMC), maximum concentrations and specific sediment loads. Moreover, a comprehensive statistical study including parameter correlation and cumulative probability analyses helped to understand the pollutant mobilization behaviour within the quarry system. It can be concluded that mobilized contamination shows the anomalous presence of some metals, whose concentrations are in excess when compared to the natural rock. This excess metal amount must be attributed to an anthropogenic source associated to mining and cutting operations.  相似文献   

Seasonal precipitation reconstruction and teleconnections with ENSO based on tree ring analysis of Pinus cooperi     

Marín Pompa-García  Enrique Jurado 《Theoretical and Applied Climatology》2014,117(3-4):495-500

Tendencies of climatic variability indicate that northern Mexico will soon suffer from severe drought. Modeling the influence of climate and ecological processes would help researchers better understand the future implication of climatic variations. Here, we reconstructed historical seasonal precipitation using dendrochronological indices of Pinus cooperi and El Niño southern oscillation (ENSO). Correlation analysis was conducted to establish the precipitation response period; then a reconstruction model using independent variables was constructed using regression procedures. Available data were calibrated and verified to strengthen and validate the modeled reconstruction. Precipitation from the previous winter was best correlated with tree growth. Regression procedures showed that the residual chronology associated in a linear model with El Niño 3.4 explained 47 % of seasonal precipitation variability. This study contributes to a better understanding of historical variations in precipitation and the influence of ENSO in common tree species of northern Mexico to help land managers improve local forest management in a climate change scenario.  相似文献   

Hydrogeochemistry and isotope techniques to determine water interactions in groundwater-dependent shallow lakes,Wet Pampa Plain,Argentina   总被引：1，自引：0，他引：1  

Asunción Romanelli  Orlando Mauricio Quiroz Londoño  Daniel Emilio Martínez  Héctor Enrique Massone  Alicia Haydée Escalante 《Environmental Earth Sciences》2014,71(4):1953-1966

This paper gives an account of the implementation of hydrochemical and isotopic techniques to identify and explain the processes that govern solute exchange in two groundwater-dependent shallow lakes in the Southeastern Pampa Plain of Argentina. Water samples (lakes, streams, spring water and groundwater) for hydrochemical and stable isotopic determination were collected and the main physical–chemical parameters were measured. The combination of stable isotope data with hydrogeochemical techniques was used for the identification of sources and preferential recharge areas to these aquatic ecosystems which allowed the explanation of the lake water origin. The hydrochemical processes which explain Los Padres Lake water chemistry are evaporation from groundwater, CO₂ input, calcite dissolution, Na⁺ release by Ca²⁺ and Mg²⁺ exchange, and sulfate reduction. The model that best aligns with La Brava Lake hydrochemical constraints includes: mixing, CO₂ and calcite dissolution, cationic exchange with Na⁺ release and Mg²⁺ adsorption, and to a lesser extent, Ca/Na exchange. This model suggests that the fractured aquifer contribution to this water body is greater than 50 %. An isotopic-specific fingerprint for each lake was identified, finding a higher evaporation rate for La Brava Lake compared to Los Padres Lake. Isotopic data demonstrate the importance of these shallow lakes as recharge areas to the regional aquifer, becoming areas of high groundwater vulnerability. The Tandilia Range System, considered in many hydrogeological studies as the impermeable bedrock of the Pampean aquifer, acts as a fissured aquifer in this area, contributing to low salinity waters and with a fingerprint similar to groundwater isotopic composition.  相似文献   

Steerable wavelet analysis of CMB structures alignment   总被引：2，自引：0，他引：2  

Patricio Vielva  Yves Wiaux  Enrique Martínez-Gonzlez  Pierre Vandergheynst 《New Astronomy Reviews》2006,50(11-12):880

This paper reviews the application of a novel methodology for analysing the isotropy of the universe by probing the alignment of local structures in the CMB. The strength of the proposed methodology relies on the steerable wavelet filtering of the CMB signal. One the one hand, the filter steerability renders the computation of the local orientation of the CMB features affordable in terms of computation time. On the other hand, the scale-space nature of the wavelet filtering allows to explore the alignment of the local structures at different scales, probing possible different phenomena. We present the WMAP first-year data analysis recently performed by the same authors (Wiaux et al.), where an extremely significant anisotropy was found. In particular, a preferred plane was detected, having a normal direction with a northern end position at (θ, ) = (34°, 331°), close to the northern end of the CMB dipole axis. In addition, a most preferred direction was found in that plane, with a northern end direction at (θ, ) = (71°, 91°), very close to the north ecliptic pole. This result synthesised for the first time previously reported anomalies identified in the direction of the dipole and the ecliptic poles axes. In a forthcoming paper (Vielva et al.), we have extended our analysis to the study of individual frequency maps finding first indications for discarding foregrounds as the origin of the anomaly. We have also tested that the preferred orientations are defined by structures homogeneously distributed in the sky, rather than from localised regions. We have also analysed the WMAP 3-year data, finding the same anomaly pattern, although at a slightly lower significance level.  相似文献   

Control of the seismic response of a composite tall building modelled by two interconnected shear beams     

J. Enrique Luco  Francisco C. P. De Barros 《地震工程与结构动力学》1998,27(3):205-223

The possibility of controlling the seismic response of tall buildings by use of a structural system consisting of a stiff and lightly damped external structure and a very flexible and moderately damped internal structure connected by stiff links at a few elevations is explored. Optimal damping values for the internal structure are obtained by consideration of the response on the composite structure in the vicinity of its fundamental mode. The resulting optimal damping values depend on the relative stiffness of both structures. Numerical results in the frequency and time domain are used to illustrate the advantages of such a system for seismic excitation. The possibility of using flexible links between the internal and external structures to moderate the required reduction of stiffness in the internal structure is also explored. © 1998 John Wiley & Sons, Ltd.  相似文献