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

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.     

Complexity‐reduction modelling for assessing the macro‐scale patterns of historical soil moisture in the Euro‐Mediterranean region

Complexity‐reduction modelling can be useful for increasing the understanding of how the climate affects basin soil moisture response upon historical times not covered by detailed hydrological data. For this purpose, here is presented and assessed an empirical regression‐based model, the European Soil Moisture Empirical Downscaling (ESMED), in which different climatic variables, easily available on the web, are addressed for simplifying the inherent complexity in the long‐time studies. To accommodate this simplification, the Palmer Drought Severity Index, the precipitation, the elevation and the geographical location were used as input data in the ESMED model for predicting annual soil moisture budget. The test area was a large region including central Europe and Mediterranean countries, and the spatial resolution was initially set at 50 km. ESMED model calibration was made according to the soil moisture values retrieved from the Terrestrial Water Budget Data archive by selecting randomly 285 grid points (out of 2606). Once parameterized, ESMED model was performed at validation stage both spatially and temporally. The spatial validation was made for the grid points not selected in the calibration stage while the comparison with the soil moisture outputs of the Global Land Data Assimilation System–NOAH10 simulations upon the period 1950–2010 was carried out for the temporal validation. Moreover, ESMED results were found to be in good agreement with a root‐zone soil moisture product obtained from active and passive microwave sensors from various satellite missions. ESMED model was thus found to be reliable for both the temporal and spatial validations and, hence, it might represent a useful tool to characterize the long‐term dynamics of soil moisture–weather interaction. Copyright © 2013 John Wiley & Sons, Ltd.     

How the aggressiveness of rainfalls in the Mediterranean lands is enhanced by climate change

Rainfall and overland flow are fundamental processes for Earth’s ecosystems but can also be land disturbing forces, particularly when triggered by extreme hydro-meteorological events. Examples of these extremes are rainstorms and related phenomena due to rainfall aggressiveness. They produce high-impact land processes such as soil erosion and nutrient losses. Economic and social consequences of these processes can be quite severe. However, hydrological extremes and their environmental implications are still poorly understood, particularly if analyzed in the context of climate change. Here, we analyze a 300 year long times series of historical rainfall patterns across the Mediterranean in the last three centuries and we investigate changes in the erosive forcing as related to climate changes. Our results show that the erosive forcing increased towards the end of the Little Ice Age (~1850) over western and central Mediterranean and that has been increasing in the recent warming period at low Mediterranean latitudes, due to a higher frequency of intensive storms. Such increased concentrated precipitation may lead to an intensification of land degradation processes triggered by soil erosion and transport across a range of scales from hillslopes to small catchments.     

Hydrogeological study of the intensely exploited aquifer of the Santa Croce leather-producing district, Tuscany (central Italy)

A hydrogeological study was undertaken to define the groundwater circulation in the Santa Croce area (Tuscany, central Italy) where the existing multilayered aquifer has long been intensively exploited. Investigations carried out on about 150 wells revealed the existence of a deep piezometric depression (to 20?m below sea level) which drains groundwater from the entire surrounding area. Samples from about 70 water points, collected twice in 2007, were analysed for major elements and stable isotope composition. Three major groups of waters, which mix in the study area, have been distinguished: (1) waters of the Ca?CMg?CHCO₃ type mainly flowing along the Arno River Plain; (2) waters of the Na?CK?CCl/Ca?CMg?CHCO₃?CSO_4, type with SO₄ content up to 275?mg/L, inflowing from the Pisane Hills; (3) relatively high-salinity waters mainly of the Na?CHCO₃ type which, with Cl concentrations up to 750?mg/L, likely arise from a normal fault located at the foot of the northern hills. The characteristics of the different components are greatly affected by significant modifying processes such as cation exchange and sulfate reduction. The achieved conceptual model suggests the southern hills as the main recharging area of the aquifer system from which water circulation, characterized by pathways of different length and depth, develops.     

Enhanced propagation of rainfall kinetic energy in the UK

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...     

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

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.     

Tectonic significance of different block-in-matrix structures in exhumed convergent plate margins: examples from oceanic and continental HP rocks in Inner Western Alps (northwest Italy)

In the Inner Western Alps, three different types of block-in-matrix structures (BIMs) formed sequentially through time at a convergent plate margin. These show the superposition of progressive deformation from (i) subduction to eclogite-facies depths, (ii) collision, accretion, and exhumation of oceanic crust, represented by the Monviso Meta-ophiolite Complex, to (iii) collision, accretion, and exhumation of the continental Dora Maira units. The Type 1 occurs in the metasedimentary cover of the Dora Maira Unit and consists of a map-scale broken formation with boudinaged ‘native’ blocks of marble (Early Jurassic) in a calcschist matrix. It results from the tectonic overprinting of exhumation-related folding (D2-stage) on an earlier subduction-related dismembered succession (D1-stage). Type 1 also includes ‘non-mappable’ BIMs with ‘exotic’ blocks, resulting from the gravitational collapse of the Triassic carbonate platform of European Continental Margin, triggered by the Early Jurassic rifting. In the Monviso Meta-ophiolite Complex, Types 2 and 3 represent tectonically induced broken and dismembered formations, respectively. They differ from each other in the degree of stratal disruption of primary interbedded horizons of mafic metabreccia (Type 3) and mafic metasandstone (Types 2 and 3) sourced by the Late Jurassic–Early Cretaceous denudation of an oceanic core complex. Dismembered interbeds (Type 2) and isolated blocks were mixed together (Type 3) by the overlap of D2 tectonics and late- to post-exhumation extensional shearing (D3-stage). Development of these types of BIMs may be common in many exhumed convergent plate margins, where severe tectonics and metamorphic recrystallization under high-pressure conditions normally prevent the reconstruction of BIMs or mélange-forming processes. Our findings show that documenting the mode and time of the processes forming BIMs is highly relevant in order to reconstruct the oceanic seafloor morphology and composition of associated stratigraphic successions, and their control in the evolution of those convergent plate margins.     

Revised seismotectonic model of NE Italy and W Slovenia based on focal mechanism inversion

The study is focusing on the stress and strain inversions from focal mechanisms in a revised seismotectonic zonation of northeastern Italy and western Slovenia. The recent increase of monitoring capability of the local seismic network, the updated geological-structural model of the area, and the novelties emerged from studies on the spatial organization of the seismicity allowed a redefinition of the seismotectonic zones. The stress and strain tensors inversion is inferred from 203 focal mechanisms, corresponding to earthquakes occurred between 1984 and 2016 with coda-duration magnitude range from 2.0 to 5.6. The inverted stress domains reveal an articulated picture of the interaction of the Adria microplate with the Eurasian plate. A dominant strike-slip stress field characterizes the eastern part of the area, while the seismotectonic zones of the central part are undergoing to thrusting regime. The stress pattern inferred in the western part of the study area outlines a complex picture with prevailing strike-slip regime and dominant compression only in a seismotectonic zone. The comparison of stress and strain tensor orientations evidences a relative uniformity of the crustal strength in the eastern and northwestern zones of the study area. The central and western zones appear to be characterized by planes of mechanical weakness not favorably oriented for failure with respect to the stress tensor.     

Fragility functions and floor spectra of RC masonry infilled frames: influence of mechanical properties of masonry infills

A wide number of experimental studies conducted in latest years pointed out the high influence of the mechanical properties of masonry units and mortar bed joints on lateral strength and stiffness of masonry panels. This feature significantly modifies the global response of infilled frames under seismic actions as well as the local interaction phenomena. Despite a wide investigation on the influence of the infills on global behaviour of reinforced concrete (RC) frames has already been provided, different features characterizing the seismic performances of buildings suggest the need of accurately evaluating local interaction phenomena as well as the influence of the panel on specific and relevant aspects, as the accelerations transferred to non-structural components. This study provides a parametrical analysis of the influence of shear strength and elastic modulus of masonry infills on the seismic behaviour of RC frames originally designed for gravity loads. Regular buildings with different height were analysed using the Incremental Dynamic Analysis in order to provide fragility curves, investigate on the collapse mechanisms and define the floor spectra depending on the properties of the infills. Results obtained pointed out the high influence of the considered parameters on the fragility of existing RC frames, often characterized by inadequate transversal reinforcement of columns, which may lead to brittle failure due to the interaction with the infills. Floor response spectra are also significantly affected by the influence of masonry infills both in terms of shape and maximum spectral accelerations. Lastly, on the basis of the observed failure mechanisms, a parameter defining the ductility of the frames depending on the properties of the infills was also provided (Capacity Design Factor). The correlation between the mechanical properties of the infills and this parameter suggests its reliability in the simplified vulnerability analysis of existing buildings as well as for the design of new buildings.     

Conceptualization and Calibration of Anisotropic Alluvial Systems: Pitfalls and Biases

Physical properties of alluvial environments typically feature a high degree of anisotropy and are characterized by dynamic interactions between the surface and the subsurface. Hydrogeological models are often calibrated under the assumptions of isotropic hydraulic conductivity fields and steady-state conditions. We aim at understanding how these simplifications affect predictions of the water table using physically based models and advanced calibration and uncertainty analysis approaches based on singular value decomposition and Bayesian analysis. Specifically, we present an analysis of the information content provided by steady-state hydraulic data compared to transient data with respect to the estimation of aquifer and riverbed hydraulic properties. We show that assuming isotropy or fixed anisotropy may generate biases both in the estimation of aquifer and riverbed parameters as well as in the predictive uncertainty of the water table. We further demonstrate that the information content provided by steady-state hydraulic heads is insufficient to jointly estimate the aquifer anisotropy together with the aquifer and riverbed hydraulic conductivities and that transient data can help to reduce the predictive uncertainty to a greater extent. The outcomes of the synthetic analysis are applied to the calibration of a dynamic and anisotropic alluvial aquifer in Switzerland (The Rhône River). The results of the synthetic and real world modeling and calibration exercises documented herein provide insight on future data acquisition as well as modeling and calibration strategies for these environments. They also provide an incentive for evaluation and estimation of commonly made simplifying assumptions in order to prevent underestimation of the predictive uncertainty.