Groundwater mixing in the discharge area of San Vittorino Plain (Central Italy): geochemical characterization and implication for drinking uses     

Maurizio Barbieri  Angela Nigro  Marco Petitta 《Environmental Earth Sciences》2017,76(11):393

Discharge areas of carbonate fractured and karstified aquifers are a sensitive system of great interest, where frequently groundwater resources are tapped for drinking water supply. In geological settings affected by recent and/or active tectonics, mixing between fresh water coming from recharge areas and groundwater from deeper circuits, influenced by raising fluids, influences hydrogeochemistry. Surveys on major ions, trace elements and stable isotopes have been performed in the San Vittorino Plain (Central Italy), where the major source of drinking water for Rome is located (Peschiera Springs, mean discharge 18 m³ s^?1, half of them tapped). Results of 21 springs revealed different contribution from recharge areas and deep flow paths, by increasing salinity and ion content, with particular references to Ca²⁺, HCO₃ ^? and SO₄ ^2?. Three main groups, respectively, related to fresh waters from recharge areas, groundwater from deep contribution and a mixing group between them, have been identified. Water stable isotopes allow to identify the common origin from rainfall and a very steady contribution with seasons and year, due to the huge extent of recharge area (>1000 km²). Saturation Indexes gave insight on the contribution of deep fluids, mainly CO₂ and H₂S, which turned groundwater to undersaturated conditions, facilitating rock dissolution. By PHREEQC software, the mixing between two considered end-members has been simulated, evaluating about 25% of deep contribution in the basal springs of San Vittorino Plain. Chemistry of Peschiera spring reveals a very limited percentage of deep flow paths (10%), which can lead to slight hydrochemistry changes even in possible drought conditions, when discharge can decrease until 15 m³ s^?1.  相似文献   

The Tagliamento River: A model ecosystem of European importance   总被引：5，自引：0，他引：5  

Klement?TocknerEmail author  James?V.?Ward  David?B.?Arscott  Peter?J.?Edwards  Johannes?Kollmann  Angela?M.?Gurnell  Geoffrey?E.?Petts  Bruno?Maiolini 《Aquatic Sciences - Research Across Boundaries》2003,65(3):239-253

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Reductive dissolution of goethite and the subsequent transformation of 4-cyanonitrobenzene: Role of ascorbic acid and pH     

Jean M. Smolen  Megan A. McLaughlin  Michael J. McNevin  Angela Haberle  Shannon Swantek 《Aquatic Sciences - Research Across Boundaries》2003,65(3):308-315

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Palaeoclimatic implications of isotopic data from modern and early Holocene shells of the freshwater snail Melanoides tuberculata, from lakes in the Ethiopian Rift Valley     

Melanie J. Leng  Angela L. Lamb  Henry F. Lamb  Richard J. Telford 《Journal of Paleolimnology》1999,21(1):97-106

Carbon and oxygen isotope ratios in the shells of the freshwater snail Melanoides tuberculata yield information on the isotopic composition of the water in which the shell was formed, which in turn relates to climatic conditions prevailing during the snails' life span. Melanoides is particularly important because it is widespread in Quaternary deposits throughout Africa and Asia and is ubiquitous in both fresh and highly evaporated lakes. Whole-shell and incremental growth data were collected from modern and fossil shells from two lakes in the Ethiopian Rift Valley. 18O values in the modern shells from Lake Awassa are in equilibrium with modern waters, while 18O values in subfossil shells from the margins of Lake Tilo indicate high rainfall during the early Holocene. Sequential analysis along the growth spiral of the shell provides information on seasonal or shorter-term variability of lake water during the lifetime of the organism.  相似文献   

Malpasset Dam discussion — Remembrances of failures of dams     

J. Laginha Serafim 《Engineering Geology》1987,24(1-4):355-366

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Climatic and non-climatic effects on the δO and δC compositions of Lake Awassa, Ethiopia, during the last 6.5 ka     

Angela L. Lamb  Melanie J. Leng  Henry F. Lamb  Richard J. Telford  Mohammed Umer Mohammed 《Quaternary Science Reviews》2002,21(20-22)

A comparison of a 6450 ¹⁴C yr δ¹⁸O and δ¹³C record of authigenic calcite from Lake Awassa, Ethiopia, with other proxy climate records in the area suggests that the lake records long-term regional climate changes. Co-varying and increasing δ¹⁸O and δ¹³C values from 4800 BP suggest an aridification of climate after the early Holocene insolation maximum. After 4000 BP, humid conditions return until after 2800 BP when δ¹⁸O increases again, reflecting more arid conditions recorded elsewhere in Ethiopia. In addition to these long-term changes, there are abrupt decreases in both δ¹⁸O_calcite and δ¹³C_calcite immediately after tephra layers. The likeliest explanation for these abrupt decreases in isotopes is the effect of tephra on the lake's catchment vegetation. δ¹⁸O, δ¹³C and lake-level measurements from Lake Awassa since the 1970s suggest that the lake is currently isotopically sensitive to short-term (annual–decadal) climate change. However, during this period, the catchment has undergone progressive deforestation that may have caused an increase in runoff. Caution is therefore required when reconstructing palaeoclimates as a contemporary lake may not always be a good analogue for lake hydrology in the past.  相似文献   

A critical assessment of the analysis and distributions of scytonemin and related UV screening pigments in sediments   总被引：1，自引：0，他引：1  

Angela H. Squier  Dominic A. Hodgson  Brendan J. Keely   《Organic Geochemistry》2004,35(11-12):1221

High performance liquid chromatography-mass spectrometry has been used to identify the cyanophyta-derived ultraviolet screening pigment scytonemin and its reduced counterpart in an Antarctic lake sediment. The formation of an artefact during the analysis has been demonstrated, enabling the recovery of improved estimates of the scytonemin and reduced scytonemin signals. The overall pigment composition records a primary producer community comprising both oxygenic and anoxygenic photoautotrophs, with variations in the abundance of scytonemin relative to the chlorophylls and carotenoids that are consistent with changes in response to variations in the light regime over time.  相似文献   

Sub-solidus reactions and corona structures in the Niquelândia layered complex (Central Goiás,Brazil)     

Dr. Maria Angela Fornoni Candia  Dr. Maurizio Mazzucchelli  Dr. Franca Siena 《Mineralogy and Petrology》1989,40(1):17-37

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Analysis of damaged concrete frames for cyclic loads     

Christian Meyer  Magdy S. L. Roufaiel  Serafim G. Arzoumanidis 《地震工程与结构动力学》1983,11(2):207-228

A mathematical model for reinforced concrete frame members is presented, which is different from others presented in the literature in that the finite size of the plastic regions is taken into account. Moreover, the model requires the specification of only elementary material properties of steel and concrete to simulate the complete behaviour under strong cyclic loads. To facilitate the analysis of damaged concrete frames, element and global damage parameters are introduced which permit the estimation of all initial conditions from only a few basic variables which can be obtained from post-earthquake field inspections, such as the residual roof displacement. The accuracy of the model is demonstrated in a series of three examples wherein analytical response predictions are compared with available experimental test data.  相似文献   

Palaeoclimate estimates for the Middle Miocene Schrotzburg flora (S Germany): a multi-method approach   总被引：3，自引：0，他引：3  

Dieter Uhl  Angela A. Bruch  Christopher Traiser  Stefan Klotz 《International Journal of Earth Sciences》2006,95(6):1071-1085

We present a detailed palaeoclimate analysis of the Middle Miocene (uppermost Badenian–lowermost Sarmatian) Schrotzburg locality in S Germany, based on the fossil macro- and micro-flora, using four different methods for the estimation of palaeoclimate parameters: the coexistence approach (CA), leaf margin analysis (LMA), the Climate-Leaf Analysis Multivariate Program (CLAMP), as well as a recently developed multivariate leaf physiognomic approach based on an European calibration dataset (ELPA). Considering results of all methods used, the following palaeoclimate estimates seem to be most likely: mean annual temperature ∼15–16°C (MAT), coldest month mean temperature ∼7°C (CMMT), warmest month mean temperature between 25 and 26°C, and mean annual precipiation ∼1,300 mm, although CMMT values may have been colder as indicated by the disappearance of the crocodile Diplocynodon and the temperature thresholds derived from modern alligators. For most palaeoclimatic parameters, estimates derived by CLAMP significantly differ from those derived by most other methods. With respect to the consistency of the results obtained by CA, LMA and ELPA, it is suggested that for the Schrotzburg locality CLAMP is probably less reliable than most other methods. A possible explanation may be attributed to the correlation between leaf physiognomy and climate as represented by the CLAMP calibration data set which is largely based on extant floras from N America and E Asia and which may be not suitable for application to the European Neogene. All physiognomic methods used here were affected by taphonomic biasses. Especially the number of taxa had a great influence on the reliability of the palaeoclimate estimates. Both multivariate leaf physiognomic approaches are less influenced by such biasses than the univariate LMA. In combination with previously published results from the European and Asian Neogene, our data suggest that during the Neogene in Eurasia CLAMP may produce temperature estimates, which are systematically too cold as compared to other evidence. This pattern, however, has to be further investigated using additional palaeofloras.Dedicated to Prof. Dr. Harald Walther, Dresden, on the occasion of his 75th birthday.  相似文献