Transport of trace elements under different seasonal conditions: Effects on the quality of river water in a Mediterranean area   总被引：1，自引：0，他引：1  

Rosa Cidu  Riccardo Biddau 《Applied Geochemistry》2007,22(12):2777

Concentrations of total and dissolved elements were determined in 35 water samples collected from rivers in Sardinia, a Mediterranean island in Italy. The overall composition did not change for waters sampled in both winter and summer (i.e., January at high-flow condition and June at low-flow condition), but the salinity and concentrations of the major ions increased in summer. Concentrations of elements such as Li, B, Mn, Rb, Sr, Mo, Ba and U were higher in summer with only small differences between total and dissolved (i.e., in the fraction <0.4 μm) concentrations. The fact that these elements are mostly dissolved during low flow periods appears to be related to the intensity of water–rock interaction processes that are enhanced when the contribution of rainwater to the rivers is low, that is during low-flow conditions. In contrast, the concentrations of Al and Fe were higher in winter during high flow with total concentrations significantly higher than dissolved concentrations, indicating that the total amount depends on the amount of suspended matter. In waters filtered through 0.015 μm pore-size filters, the concentrations of Al and Fe were much lower than in waters filtered through 0.4 μm pore-size filters, indicating that the dissolved fraction comprises very fine particles or colloids. Also, Co, Ni, Cu, Zn, Cd and Pb were generally higher in waters collected during the high-flow condition, with much lower concentrations in 0.015 μm pore-size filtered waters; this suggests aqueous transport via adsorption onto very fine particles. The rare earth elements (REE) and Th dissolved in the river waters display a wide range in concentrations (∑REE: 0.1–23 μg/L; Th: <0.005–0.58 μg/L). Higher REE and Th concentrations occurred at high flow. The positive correlation between ∑REE and Fe suggests that the REE are associated with very fine particles (>0.015 and <0.4 μm); the abundance of these particles in the river controls the partitioning of REE between solution and solid phases.Twenty percent of the water samples had dissolved Pb and total Hg concentrations that exceeded the Italian guidelines for drinking water (>10 μg/L Pb and >1 μg/L Hg). The highest concentrations of these heavy metals were observed at high-flow conditions and they were likely due to the weathering of mine wastes and to uncontrolled urban wastes discharged into the rivers.  相似文献   

Kinematics of the Western Africa-Eurasia plate boundary from focal mechanisms and GPS data   总被引：6，自引：0，他引：6  

E. Serpelloni  G. Vannucci  S. Pondrelli  A. Argnani  G. Casula  M. Anzidei  P. Baldi  P. Gasperini 《Geophysical Journal International》2007,169(3):1180-1200

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Hydrogeological and multi-isotopic approach to define nitrate pollution and denitrification processes in a coastal aquifer (Sardinia,Italy)     

Daniele Pittalis  Raul Carrey  Stefania Da Pelo  Alberto Carletti  Riccardo Biddau  Rosa Cidu  Fulvio Celico  Albert Soler  Giorgio Ghiglieri 《Hydrogeology Journal》2018,26(6):2021-2040

Agricultural coastal areas are frequently affected by the superimposition of various processes, with a combination of anthropogenic and natural sources, which degrade groundwater quality. In the coastal multi-aquifer system of Arborea (Italy)—a reclaimed morass area identified as a nitrate vulnerable zone, according to Nitrate Directive 91/676/EEC—intensive agricultural and livestock activities contribute to substantial nitrate contamination. For this reason, the area can be considered a bench test for tuning an appropriate methodology aiming to trace the nitrate contamination in different conditions. An approach combining environmental isotopes, water quality and hydrogeological indicators was therefore used to understand the origins and attenuation mechanisms of nitrate pollution and to define the relationship between contaminant and groundwater flow dynamics through the multi-aquifer characterized by sandy (SHU), alluvial (AHU), and volcanic hydrogeological (VHU) units. Various groundwater chemical pathways were consistent with both different nitrogen sources and groundwater dynamics. Isotope composition suggests a mixed source for nitrate (organic and synthetic fertilizer), especially for the AHU and SHU groundwater. Moreover, marked heterotrophic denitrification and sulfate reduction processes were detected; although, for the contamination related to synthetic fertilizer, the attenuation was inefficient at removing NO₃^? to less than the human consumption threshold of 50 mg/L. Various factors contributed to control the distribution of the redox processes, such as the availability of carbon sources (organic fertilizer and the presence of lagoon-deposited aquitards), well depth, and groundwater flow paths. The characterization of these processes supports water-resource management plans, future actions, and regulations, particularly in nitrate vulnerable zones.  相似文献   

Integration of rainfall thresholds and susceptibility maps in the Emilia Romagna (Italy) regional-scale landslide warning system   总被引：2，自引：2，他引：0  

Samuele Segoni  Daniela Lagomarsino  Riccardo Fanti  Sandro Moretti  Nicola Casagli 《Landslides》2015,12(4):773-785

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Exploring controls of the early and stepped deglaciation on the western margin of the British Irish Ice Sheet     

Sara Benetti  Richard C. Chiverrell  Colm Ó Cofaigh  Matt Burke  Alicia Medialdea  David Small  Colin Ballantyne  Mark D. Bateman  S. Louise Callard  Peter Wilson  Derek Fabel  Chris D. Clark  Riccardo Arosio  Sarah Bradley  Paul Dunlop  Jeremy C. Ely  Jenny Gales  Stephen J. Livingstone  Steven G. Moreton  Catriona Purcell  Margot Saher  Kevin Schiele  Katrien Van Landeghem  Kasper Weilbach 《第四纪科学杂志》2021,36(5):833-870

New optically stimulated luminescence dating and Bayesian models integrating all legacy and BRITICE-CHRONO geochronology facilitated exploration of the controls on the deglaciation of two former sectors of the British–Irish Ice Sheet, the Donegal Bay (DBIS) and Malin Sea ice-streams (MSIS). Shelf-edge glaciation occurred ~27 ka, before the global Last Glacial Maximum, and shelf-wide retreat began 26–26.5 ka at a rate of ~18.7–20.7 m a^–1. MSIS grounding zone wedges and DBIS recessional moraines show episodic retreat punctuated by prolonged still-stands. By ~23–22 ka the outer shelf (~25 000 km²) was free of grounded ice. After this time, MSIS retreat was faster (~20 m a^–1 vs. ~2–6 m a^–1 of DBIS). Separation of Irish and Scottish ice sources occurred ~20–19.5 ka, leaving an autonomous Donegal ice dome. Inner Malin shelf deglaciation followed the submarine troughs reaching the Hebridean coast ~19 ka. DBIS retreat formed the extensive complex of moraines in outer Donegal Bay at 20.5–19 ka. DBIS retreated on land by ~17–16 ka. Isolated ice caps in Scotland and Ireland persisted until ~14.5 ka. Early retreat of this marine-terminating margin is best explained by local ice loading increasing water depths and promoting calving ice losses rather than by changes in global temperatures. Topographical controls governed the differences between the ice-stream retreat from mid-shelf to the coast.  相似文献   

Analytical and numerical modelling of air trapping during wetting of unsaturated soils     

Scarfone  Riccardo  Wheeler  Simon J. 《Acta Geotechnica》2022,17(8):3499-3513

Acta Geotechnica - At high values of degree of saturation, the apparent soil water retention curve (SWRC) measured in a wetting test in the laboratory may differ from the true SWRC, because of the...  相似文献   

Yield and catch changes in a Mediterranean small tuna trap: a warming change effect?          下载免费PDF全文

Riccardo Cattaneo‐Vietti  Valentina Cappanera  Michela Castellano  Paolo Povero 《Marine Ecology》2015,36(2):155-166

Since the 17th century, the Tonnarella of Camogli, a small tuna trap, has been used to catch pelagic fish along the western coast of the Portofino Promontory (Ligurian Sea, Northwestern Mediterranean). The availability of long‐term datasets on fish yields (1950–1974 and 1996–2011), with information related to the seawater temperatures and the North Atlantic Oscillation (NAO), has allowed us to study the qualitative and quantitative changes in fish yields in the last decade and the possible relationships with the seasonal anomalies of temperature that have occurred in the Ligurian Sea. In 1950–1974, yields remained relatively constant over time (average of 35.6 ± 8.7 t·year^?1). From 1996 through 2011, yields were high (42.9 ± 15.9 t·year^?1) but inconsistent with strong annual variability in catches. The primary catches are Seriola dumerili, Auxis rochei, Trachurus spp. and Sarda sarda. Changes in species composition have occurred as well: S. dumerili, Sardinella sp. and Belone belone have appeared recently. Moreover, a significant decrease in the boreal scombroid (Scomber scombrus) and an increase of warm‐temperate carangids and other typically Southern Mediterranean species such as Coryphaena hippurus and Sphyraena viridensis, appear to be linked to the warming of the surface water layer, particularly evident in the Ligurian Sea, for the last 10 years. The analysis of this kind of trend may be a powerful tool for assessing structural changes of the pelagic fish community in the Ligurian Sea (Northwestern Mediterranean).  相似文献   

Long‐term comparison of structure and dynamics of the red coral metapopulation of the Portofino Promontory (Ligurian Sea): a case‐study for a Marine Protected Area in the Mediterranean Sea          下载免费PDF全文

Giorgio Bavestrello  Marzia Bo  Marco Bertolino  Federico Betti  Riccardo Cattaneo‐Vietti 《Marine Ecology》2015,36(4):1354-1363

A large amount of data on the precious coral Corallium rubrum has attested to a dramatic shift in the size structure of its over‐harvested Mediterranean populations in recent decades. One of the main problems for the conservation of this species is the substantial lack of data concerning the time span necessary for a population subjected to pluri‐decennial harvesting pressure to return to its pristine status. Here, we present a multi‐annual data set gathered from the Marine Protected Area (MPA) of Portofino, which hosts the most important shallow‐water coral populations in the Ligurian Sea and was subjected to strong harvesting pressure from the 1950s to the early 1970s. Quantitative comparison of the population structure data recorded in 1964, 1990 and 2012 indicated a strong size increase of the colonies (from 3 to 8 g mean weight), resulting in an increase in colony biomass from 300 to the current 1500 g·m^?2. As a consequence, over the same span of time, the density of colonies has slightly decreased. The role of mass mortality phenomena, like that occurred in this area during 1999, as possible biological features triggering the switch of red coral populations from a ‘grass plain‐like’ towards a ‘forest‐like’ structure, is discussed. All these data indicate that the instigation of MPAs is a winning strategy in the conservation of this precious species and similar management plans should also be evaluated for the protection of the deep benthic communities thriving on off‐shore banks.  相似文献   

Extragalactic HI surveys     

Riccardo?GiovanelliEmail author  Martha?P.?Haynes 《Astronomy and Astrophysics Review》2016,24(1):1-57

We review the results of HI line surveys of extragalactic sources in the local Universe. In the last two decades major efforts have been made in establishing on firm statistical grounds the properties of the HI source population, the two most prominent being the HI Parkes All Sky Survey and the Arecibo Legacy Fast ALFA survey. We review the choices of technical parameters in the design and optimization of spectro-photometric “blind” HI surveys, which for the first time produced extensive HI-selected data sets. Particular attention is given to the relationship between optical and HI populations, the differences in their clustering properties and the importance of HI-selected samples in contributing to the understanding of apparent conflicts between observation and theory on the abundance of low mass halos. The last section of this paper provides an overview of currently ongoing and planned surveys which will explore the cosmic evolution of properties of the HI population.  相似文献   

Analysis of Ground Deformation Detected Using the SBAS-DInSAR Technique in Umbria, Central Italy   总被引：1，自引：0，他引：1  

Fausto Guzzetti  Michele Manunta  Francesca Ardizzone  Antonio Pepe  Mauro Cardinali  Giovanni Zeni  Paola Reichenbach  Riccardo Lanari 《Pure and Applied Geophysics》2009,166(8-9):1425-1459

Ground deformation affecting the Umbria region (central Italy) in the 9-year period from 1992 to 2000 was investigated through multi-temporal Differential Synthetic Aperture Radar Interferometry (DInSAR). For the purpose, the Small BAseline Subset (SBAS) technique was adopted, which allows studying the temporal evolution of the detected deformation at two spatial scales: a low-resolution (regional) scale, and a full-resolution (local) scale. For the analysis, SAR data acquired by the European Remote Sensing (ERS-1/2) satellites along ascending and descending orbits were used. The detected deformation was analysed to investigate its relevance to geophysical, geomorphologic, and human-induced processes that may result in hazardous conditions to the population of Umbria. Low-resolution deformation data were used to: (i) determine the amount of displacement caused by the Umbria-Marche earthquake sequence from September 1997 to April 1998 in the Foligno area, (ii) determine the number and percentage of the known landslides that can be monitored by the DInSAR technology in the investigated area, and (iii) identify and measure subsidence induced by exploitation of a confined aquifer in the Valle Umbra. Results indicate that earthquakes moved through the Foligno area westwards up to 3.9 cm and with an uplift reaching 1.7 cm. Intersection in a GIS of the low-resolution deformation maps with a detailed landslide inventory map allowed the determination that the portion of landslides that can be monitored by the SBAS-DInSAR technique in Umbria ranges from 2.7% to 3.4%, and the percentage of the total landslide area ranges from 10.4% to 12.8%. In the Valle Umbra, a dependency was found between the time and the amount of detected ground deformation, and the record of water withdrawal. The full-resolution deformation data were used to investigate the movement of the Ivancich landslide, in the Assisi Municipality. Joint analysis of the spatial and the temporal characteristics of the ground displacement allowed the formulation of a hypothesis on the landslide geometry and deformation pattern.  相似文献