The River Arno catchment,northern Tuscany: chemistry of waters and sediments from the River Elsa and River Era sub‐basins,and sulphur and oxygen isotopes of aqueous sulphate     

Gianni Cortecci  Enrico Dinelli  Tiziano Boschetti 《水文研究》2007,21(1):1-20

Within the hydrologic balance of the River Arno catchment (northern Tuscany), the Rivers Elsa and Era are important tributaries entering the main river from the left bank in the lower part of the watershed. Waters and bed sediments were sampled in June 2000 during low discharges in the Rivers Elsa and Era, as well as in major tributary streams. Water samples were analysed for major chemistry and sulphur isotope composition of sulphate, and sediment samples were analysed for major composition and selected trace elements of environmental concern (Zn, Cu, Pb, Cr and Ni). The main results for the waters are: (1) Na and Cl in solution show consistent downstream positive trends in the main rivers, thus supporting progressive contributions of anthropogenic salts; the highest concentration values are observed in tributaries; (2) as shown by sulphur isotopes, sulphate in solution is mainly controlled by dissolution of evaporites (Elsa basin) or oxidation of reduced organic/biogenic sulphur (Era basin), with anthropogenic contributions in most streams not higher than 10% in both the basins. A δ³⁴S signature in the range ?2 to +3‰ is estimated for pollutant sulphate in the basins studied. The main results for the sediments are: (1) major chemistry is essentially controlled by the lithotypes drained by the waters; (2) pollution by heavy metals does not reach high levels; (3) compared with local fine‐grained rocks, copper is more frequently anomalous, whereas lead and zinc show only occasional anomalies; (4) local high concentrations of chromium and nickel can be attributed to upstream occurrences of ophiolites. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

The Serchio River catchment,northern Tuscany: Geochemistry of stream waters and sediments,and isotopic composition of dissolved sulfate     

Gianni Cortecci  Enrico Dinelli  Tiziano Boschetti  Paola Arbizzani  Loredana Pompilio  Mario Mussi 《Applied Geochemistry》2008

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Enhanced propagation of rainfall kinetic energy in the UK     

Diodato  Nazzareno  Bellocchi  Gianni 《Theoretical and Applied Climatology》2017,129(3-4):1335-1340

Theoretical and Applied Climatology - A gridded 0.25° reconstruction of rainfall kinetic energy (RKE) over the UK, on the basis of pluviometric observations and reanalysis back to 1765, shows...  相似文献   

The Crati Submarine Fan,Ionian Sea     

Franco Ricci Lucchi  Albina Colella  Gianni Gabbianelli  Sergio Rossi  William R. Normark 《Geo-Marine Letters》1983,3(2-4):71-77

The Crati Fan is located in the tectonically active submerged extension of the Apennines chain and foretrough. The small fan system is growing in a relatively shallow (200 to 450 m), elongate nearshore basin receiving abundant input from the Crati River. The fan is characterized by a short, steep, channelized section (inner or upper fan) and a smooth, slightly bulging distal section (outer or lower fan). The numerous subparallel channels head in the shelf or littoral zone and do not form branching distributary patterns. Sand and mud depositional lobes of the outer fan stretch over more than 60% of fan length.  相似文献   

Geochemistry of trace elements in surface waters of the Arno River Basin,northern Tuscany,Italy     

Gianni Cortecci  Tiziano Boschetti  Enrico Dinelli  Rosa Cidu  Francesca Podda  Marco Doveri 《Applied Geochemistry》2009

Trace element geochemistry of the Arno River and its main tributaries was investigated on the basis of two sampling campaigns carried out in November 1996 and June 1997. By analyzing filtered and unfiltered water samples, Fe and Al are found in solution mainly as colloidal particles of size lower than 0.45 μm. In June (lower flow rate), Fe and Al are enriched in the filtered waters from the main river, and this feature was interpreted in terms of higher water temperature promoting the formation of smaller particles, thus reducing their aggregation properties. Iron and Al show perfectly synchronous downstream profiles along the Arno River, correlate quite well each to other, and display abrupt concentration increases near to Florence, where the lithology of the catchment changes from siliciclastic dominated to clay-sand (lacustrine-marine)-dominated. The same behaviour is shown by most of the other trace elements in the river, thus supporting a general lithological control. Trace elements in the final part of the Arno River are influenced by flocculation processes in addition to mixing. Adsorption phenomena on oxy-hydroxides are denoted by good elemental correlations with Fe (and Al). Sporadic anomalous concentration values, possibly related to anthropogenic contributions, may prevent such correlations. Referring to the quality of waters for potable use and fish life, toxic elements are below the acceptable limits of current European regulations, with few exceptions for Hg exceeding guideline values. Multivariate analysis groups trace elements according to geochemical affinities and natural or anthropogenic sources, thus distinguishing contaminated from uncontaminated samples. The results achieved in this work will help regional and national Authorities for compliance with the EU water policy, especially in assessing the water quality at the river basin scale and its vulnerability to human activities.  相似文献   

Magnetic and microwave structure in solar active regions     

Marcello Felli  Giannina Poletto  Gianni Tofani 《Solar physics》1977,51(1):65-81

The structure of six active regions observed at 2.8 cm with the Stanford interferometer is compared with the configuration of the underlying photospheric magnetic fields, as given by the Kitt Peak magnetograph.The similar resolution and accuracy on the measured positions of both instruments allowed us to establish a more detailed spatial correspondence between radio and magnetic features than previously reached.The radio features which correspond to the cores of the active sources are always found to overlay regions of enhanced magnetic fields. Different spatial associations have been found depending on the brightness temperature of the sources. The possibility that this effect might be due to the development of the active region is also considered.  相似文献   

Oxygen-isotope variations in sulfate ions in the water of some Italian lakes     

Gianni Cortecci 《Geochimica et cosmochimica acta》1973,37(6):1531-1542

The results obtained by measuring the sulfate content and its $\text{O}{}^{18}\text{O}{}^{16}$ ratios through time in some volcanic, tectonic and dam Italian lakes are reported here. The variations with time of the oxygen isotopic composition of the lake waters are also reported. The measurements refer mainly to surface water; however, a few deep samples were also studied.In the case of all the lakes examined, the variations with time of the oxygen isotopic composition and of the concentration of the dissolved sulfate cannot be explained in terms of the addition and of seasonal variations of the O¹⁸ content of rainwater sulfate. Biological redox processes involving bacterial reduction of sulfate and sulfide oxidation can reasonably account for the results obtained.According to Lloyd (1967), when sulfate is formed by bacterial sulfide oxidation, 68 per cent of the sulfate oxygen is water oxygen, while 32 per cent is dissolved molecular oxygen. The isotopic enrichment of the dissolved molecular oxygen in the lake waters relative to the isotope content of the atmospheric oxygen is mainly related to the biological activity in the waters.Assuming that a stagnation period takes place during summer and fall while a period of strong bio-respiratory activity takes place during winter and spring, it follows that a small isotope fractionation effect on molecular dissolved oxygen can be expected during stagnation while a high isotope fractionation can be expected during winter and spring. The O¹⁸ content of the sulfate dissolved in volcanic and tectonic lakes varies according to this hypothesis. The fact that similar O¹⁸ contents of the dissolved sulfate are or are not found in the same period of different years is probably related to similarities or differences in the climatic conditions.The bio-physical behaviour of the Corbara dam lake is different from that of other lakes. However, because of the continuous feeding by the Tiber River, variations of the sulfate concentration and its oxygen isotopic composition can be caused by the contribution of polluted water.  相似文献   

Numerical simulation of round robin numerical test on tunnels using a simplified kinematic hardening model   总被引：1，自引：0，他引：1  

Grigorios Tsinidis  Kyriazis Pitilakis  Areti Despina Trikalioti 《Acta Geotechnica》2014,9(4):641-659

The paper summarizes the numerical simulation of the round robin numerical test on tunnels performed in Aristotle University of Thessaloniki. The main issues of the numerical simulation are presented along with representative comparisons of the computed response with the recorded data. For the simulation, the finite element method is implemented, using ABAQUS. The analyses are performed on prototype-scale models under plane strain conditions. While the tunnel behavior is assumed to be elastic, the soil nonlinear behavior during shaking is modeled using a simplified kinematic hardening model combined with a von Mises failure criterion and an associated plastic flow rule. The model parameters are adequately calibrated using available laboratory test results for the specific fraction of sand. The soil–tunnel interface is also accounted and simulated adequately. The effect of the interface friction on the tunnel response is investigated for one test case, as this parameter seems to affect significantly the tunnel lining axial forces. Finally, the internal forces of the tunnel lining are also evaluated with available closed-form solutions, usually used in the preliminary stages of design and compared with the experimental data and the numerical predictions. The numerical analyses can generally reproduce reasonably well the recorded response. Any differences between the experimental data and the numerical results are mainly attributed to the simplification of the used model and to differences between the assumed and the actual mechanical properties of the soil and the tunnel during the test.  相似文献