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Giovanni Bearzi Arianna Azzellino Elena Politi Marina Costa Mauro Bastianini 《Ocean Science Journal》2008,43(4):175-182
Bottlenose dolphins are the only cetaceans regularly observed in the northern Adriatic Sea, but they survive at low densities
and are exposed to significant threats. This study investigates some of the factors that influence habitat use by the animals
in a largely homogeneous environment by combining dolphin data with hydrological and physiographical variables sampled from
oceanographic ships. Surveys were conducted year-round between 2003 and 2006, totalling 3,397 km of effort. Habitat modelling
based on a binary stepwise logistic regression analysis predicted between 81% and 93% of the cells where animals were present.
Seven environmental covariates were important predictors: oxygen saturation, water temperature, density anomaly, gradient
of density anomaly, turbidity, distance from the nearest coast and bottom depth. The model selected consistent predictors
in spring and summer. However, the relationship (inverse or direct) between each predictor and dolphin presence varied among
seasons, and different predictors were selected in fall. This suggests that dolphin distribution changed depending on seasonal
forcing. As the study area is relatively uniform in terms of bottom topography, habitat use by the animals seems to depend
on complex interactions among hydrological variables, caused primarily by seasonal change and likely to determine shifts in
prey distribution. 相似文献
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Persistent organochlorines, such as polychlorinated biphenyls, including coplanar congeners and DDT compounds, were measured in the liver of a teleost species: namely, Lophius budegassa. The mean concentrations of PCBs (1249 ng/g wet wt) were comparable with DDTs mean levels (1459 ng/g wet wt). Among DDTs the compound found at the highest concentration was p,p'-DDE representing 76% of the total DDT burden. The PCB profiles were dominated by congeners 153, 180, and 138 accounting for 49.8%, 16.0% and 13.7% of the total PCBs. The total 2,3,7,8-TCDD toxic equivalent (TEQs) of six coplanar PCBs, including mono- and non-ortho congeners, was 0.98 pg/g wet wt. The congeners with highest TEQs values were non-ortho-congeners followed by mono-ortho ones. 相似文献
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Concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (DDTs), were determined in the liver of two different shark species Prionace glauca (blue shark) and Dalatias licha (kitefin shark) from the Mediterranean Sea. In blue shark liver, the concentrations of PCBs (2482 ngg(-1)) and DDTs (2392 ngg(-1)) were comparable, while in kitefin shark the hepatic concentrations of DDTs (4554 ngg(-1)) were significantly higher than those of PCBs (1827 ngg(-1)). Contamination levels differed between species, with kitefin shark showing consistently higher concentrations of DDTs, and blue shark higher levels of PCBs. Congener-specific PCB profiles, similar between the two species were dominated by the higher chlorinated congeners (hexachlorobiphenyls: 62.8-63.9%, penta-: 15.2-21.3%, hepta-: 13.4-14.5%) with most of the lower chlorinated congeners being absent or present at very low levels. In both species, the total 2,3,7,8-tetrachlorodibenz-p-dioxin toxic equivalent (TEQs) concentrations (blue shark: 2.51 pg/g; kitefin shark: 1.46 pg/g) seem to be relatively modest. Regards to DDT component pattern, p,p'-DDE was dominant in the liver of both species (blue shark: 81.5%; kitefin shark: 38.0%), while the percentage composition of the other metabolites was differently characterized. The composition pattern of DDTs and the low value of p,p'-DDE/DDTs ratio in the specimens from Ionian Sea suggest that organochlorine pesticide contamination is still continuing in this marine environment. 相似文献
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Analytical Solutions of Three‐Dimensional Contaminant Transport Models with Exponential Source Decay 
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下载免费PDF全文 Despite the availability of numerical models, interest in analytical solutions of multidimensional advection‐dispersion systems remains high. Such models are commonly used for performing Tier I risk analysis and are embedded in many regulatory frameworks dealing with groundwater contamination. In this work, we develop a closed‐form solution of the three‐dimensional advection‐dispersion equation with exponential source decay, first‐order reaction, and retardation, and present an approach based on some ease of use diagrams to compare it with the integral open form solution and with earlier versions of the closed‐form solution. The comparison approach focuses on the relative differences associated with source decay and the effect of simulation time. The analysis of concentration contours, longitudinal sections, and transverse sections confirms that the closed‐form solutions studied can be used with acceptable approximation in the central area of a plume bound transversely within the source width, both behind and beyond the advective front and for concentration values up to two orders of magnitude less than the initial source concentration. As the proposed closed‐form model can be evaluated without nested numerical computations and with simple mathematical functions, it can be very useful in risk assessment procedures. 相似文献
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An efficient procedure is proposed to define realistic lower limits of velocity errors of a non-permanent GPS station (NPS),
i.e., a station where the antenna is installed and operates for short time periods, typically 10–20 days per year. Moreover,
the proposed method is aimed at being independent of standard GPS data processing. The key is to subsample appropriately the
coordinate time series of several continuous GPS stations situated nearby or inside the considered NPS network, in order to
simulate the NPS behavior and to estimate the velocity errors associated with the subsampling procedure. The obtained data
are used as lower limits to accept or correct the error estimates provided by standard data processing. The proposed approach
is applied to data from the dense, non-permanent network in the Central Apennine of Italy based on a sequence of solutions
for the overlapping time spans 1999–2003, 1999–2004, 1999–2005 and 1999–2007. Both the original and error-corrected velocity
patterns are used to compute the strain rate fields. The comparison between the corresponding results reveals large differences
that could lead to divergent interpretations about the kinematics of the study area. 相似文献
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Characterization of landslide ground surface kinematics from terrestrial laser scanning and strain field computation 总被引：1，自引：0，他引：1
Assessment and mitigation of the risk induced by landslide activation need an appropriate phenomenon investigation, to obtain useful information about the failure processes. The first step is the complete kinematics characterization of the landslide ground surface, by evaluating the involved displacement and deformation patterns. A dense displacement field can be obtained from comparison of a series of multi-temporal observations performed by means of terrestrial laser scanning. Subsequently, the strain field can be computed from displacement vectors. In this paper, a modified least square technique is employed to compute the strain on the nodes of a regular grid (2D approach) or on the points of a digital terrain model (3D approach). Such a computation takes into account the displacements, their spatial distribution, as well as the measurement and modelling errors. A scale factor is introduced in order to emphasize the contributions of the experimental points on the basis of their distance from each computation point, and to recognize possible scale-depending behaviours. This method has been implemented in Matlab and applied on two landslides located in the northeastern Italian Alps (Lamosano and Perarolo di Cadore). The experiments show that different kinematics can be recognized, and the presence and influence of eventual discontinuities can be revealed. 相似文献
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