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161.
Alessandro Chelli Andrea Zanini Emma Petrella Alessandra Feo Fulvio Celico 《Environmental Earth Sciences》2018,77(6):246
In the last decades, hydraulic barriers have been activated in a large number of polluted sites with the aim of preventing groundwater pollution outside the contaminated area. From a regulatory point of view, there is the need of evaluating the efficacy of these barriers. For this reason, the goal of the present study is to apply a coupled experimental modelling approach aimed at evaluating the efficacy of the barrier and providing management strategies. In particular, a case study in Italy is investigated. The study case is of main interest because of its complexity due to a heterogeneous aquifer and the presence of surface water that interacts with the below aquifer. The study has been carried out through the experimental characterization of the aquifer system (coupling the classic stratigraphic techniques with the results of radiocarbon dating, as well as through pumping and injection tests) and its hydrogeological behaviour (by means of hydraulic- and the stream-head measurements, as well as some isotopic investigations), and the implementation of a numerical model (through MODFLOW 2005). The results show the effectiveness of the coupled experimental modelling approach to analyse and simulate the hydrodynamics within the test aquifer system, as well as to evaluate the efficacy of the hydraulic barrier. Based on the results of the numerical model, easy solutions were designed to manage the barrier. 相似文献
162.
‘Alternative’ food initiatives (AFIs) are often interpreted as political movements, constructed as defiant alternatives to industrial agri‐food relations, and represented by a performance of singular alterity. This understanding of alternative collapses into a mere politics of identity, criticised in the literature for its oversimplification. In this paper, we utilise an established methodological framework that retains AFI diversity, to create a novel typology of AFIs by diverse and embodied practice rather than animating political project. In doing so, we point to the political potential for AFIs to ‘do’ food otherwise and make different worlds. 相似文献
163.
Paolo Tomassetti Emma Persia Isabel Mercatali Danilo Vani Veronica Marussso Salvatore Porrello 《Marine pollution bulletin》2009,58(4):533-541
The effects of solid organic wastes from a marine fish farm on sediment was tested using macrobenthic fauna as biological indicators. Impact on benthic fauna was evaluated in the vicinity of a fish farm in the Tyrrhenian Sea (Western Mediterranean) between July 2001 and October 2002. Changes in benthic community structure were investigated using multivariate, distributional and univariate analyses (diversity indices, AMBI and M-AMBI). The results showed sharp disturbance of assemblages under the cages and no effects in the area more than 25 m from the cages. Sediment alterations were related to an increase in farmed biomass and its wastes, as well as to low current speed that allowed accumulation of organic matter on the sea floor. It was possible to follow the ecological succession from slightly altered assemblages to heavily polluted ones in the very short period of a single fish fattening cycle (15 months). 相似文献
164.
Communicating geomorphology: an empirical evaluation of the discipline's impact and visibility
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Concern among geomorphologists that the discipline's visibility and impact are becoming suppressed are reflected in a series of recent Earth Surface Exchanges (ESEX) commentaries by Tooth et al. This paper from the British Society for Geomorphology (BSG) Communicating Geomorphology Fixed‐Term Working Group (FTWG) reports initial findings from an online survey of BSG members alongside an empirical assessment of the term's prominence in academic output: international peer‐reviewed journals, undergraduate Geoscience degrees in world‐leading institutions and the UK Research Excellence Framework (REF) impact statements. Our observations indicate the scientific standing of the discipline has been retained but the term itself is less widely utilised and we offer a series of suggestions actionable by the geomorphology community. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
165.
Geomorphological changes in an arid transgressive coastal dune field due to natural processes and human impacts
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Antonio I. Hernández‐Cordero Luis Hernández‐Calvento Patrick A. Hesp Emma Pérez‐Chacón 《地球表面变化过程与地形》2018,43(10):2167-2180
Geomorphological changes in recent decades in an arid transgressive coastal dune system (Maspalomas, Gran Canaria, Canary Islands) are analyzed. The methodology used is based on the generation of two geomorphological maps (1961 and 2003) by interpretation of digital orthophotos. The overlay of both maps in a geographic information system (GIS) enabled the spatial and surface changes of the landforms to be determined, and the processes that generated these changes. Twelve cultural and geomorphological processes were identified from highest to lowest importance, namely: anthropization by urban occupation (114 ha changed), stabilization (92.5 ha), barchanization (37 ha), salinization/halophytication (15 ha), anthropization (12.4 ha), deflation (11.8 ha), dune loss/beach gain (11.3 ha), dune formation (9.6 ha), progradation (8 ha), retrogradation (7.7 ha), destabilization (2.7 ha) and flooding (0.7 ha). Geomorphological changes are associated with a combination of five main factors, three of anthropogenic origin and two natural ones. The natural factors are: (1) the arid climate, which favors changes occurring at high speed; (2) the existence of a progressive sedimentary deficit. Anthropogenic factors are: (3) construction of tourist urbanizations, infrastructures and facilities; (4) installation of equipment or infrastructure on the beaches; (5) the activities carried out by users. These human factors have altered the aeolian dynamics and reduced the area occupied by vegetation in some areas, causing changes in aeolian sedimentary processes. The geomorphological processes identified can be used as indicators of environmental change, allowing us to synthesize the changes in landforms detected, and group all combinations derived from the analysis by GIS and analyze them spatially. Thus, the environmental changes in the transgressive coastal dune systems could be interpreted more effectively. Copyright © 2018 John Wiley & Sons, Ltd. 相似文献
166.
167.
Water losses in the Sudd wetlands of South Sudan have significant effects on water resources available to Sudan and Egypt. These losses increased greatly after the dramatic rise of Lake Victoria in 1961–1964, but investigation into the cause and location of these increased losses has been hindered by the shortage of records after 1963 and their cessation after 1983. By linking flow records at key points within the Sudd with the distribution of vegetation before the rise, analysis of vegetation after the rise can throw light on the distribution of resulting losses and their causes. Although the increased flooding in the upper reaches of the Sudd has been noted, this paper draws attention to greatly increased inundation in the lower reaches, apparently from backwater flooding, which would affect any future proposal for the Jonglei Canal project. 相似文献
168.
Charles J. Paradis Emma R. Dixon Lauren M. Lui Adam P. Arkin Jack C. Parker Jonathan D. Istok Edmund Perfect Larry D. McKay Terry C. Hazen 《Ground water》2019,57(2):292-302
The breakthrough curve obtained from a single-well push-pull test can be adjusted to account for dilution of the injection fluid in the aquifer fluid. The dilution-adjusted breakthrough curve can be analyzed to estimate the reaction rate of a solute. The conventional dilution-adjusted method assumes that the ratios of the concentrations of the nonreactive and reactive solutes in the injection fluid vs. the aquifer fluid are equal. If this assumption is invalid, the conventional method will generate inaccurate breakthrough curves and may lead to erroneous conclusions regarding the reactivity of a solute. In this study, a new method that generates a dilution-adjusted breakthrough curve was theoretically developed to account for any possible combination of nonreactive and reactive solute concentrations in the injection and aquifer fluids. The newly developed method was applied to a field-based data set and was shown to generate more accurate dilution-adjusted breakthrough curves. The improved dilution-adjusted method presented here is simple, makes no assumptions regarding the concentrations of the nonreactive and reactive solutes in the injection and aquifer fluids, and easily allows for estimating reaction rates during push-pull tests. 相似文献
169.
This paper presents new experimental data on 2-D surf beat generation by a time-varying breakpoint induced by bichromatic wave groups. The experimental investigation covers a broad range of wave amplitudes, short wave frequencies, group frequencies and modulation rates. The data include measurements of incident and outgoing wave amplitudes, breakpoint position, shoreline run-up and the cross-shore structure of both the short and long wave motion. Surf beat generation is shown to be in good agreement with theory [Symonds, G., Huntley, D.A., Bowen, A.J., 1982. Two dimensional surf beat: long wave generation by a time-varying breakpoint. J. Geophys. Res. 87, 492–498]. In particular, surf beat generation is dependent on the normalised surf zone width, which is a measure of the phase relationship between the seaward and shoreward breakpoint forced long waves, and linearly dependent on the short wave amplitude. The cross-shore structure of the long wave motion is also consistent with theory; at maximum and minimum surf beat generation, the mean breakpoint coincides with the nodal and anti-nodal points, respectively, for a free long wave standing at the shoreline. A numerical solution, using measured data as input, additionally shows that the phase relationship between the incident bound long wave and the outgoing breakpoint forced wave is consistent with the time-varying breakpoint mechanism. 相似文献
170.
Diego Macías Gabriel Navarro Ana Bartual Fidel Echevarría I. Emma Huertas 《Estuarine, Coastal and Shelf Science》2009
Primary production was studied at nine sites distributed within the Strait of Gibraltar (Southern Spain) and North-Western (NW) Alboran Sea by analyzing photosynthesis-irradiance (P–I) relationships and integrated primary production rates in relation to the different types of Deep Chlorophyll Maxima (DCM) detected in the area. The characteristics of the DCM were examined by several methods, including flow cytometry, quantification of transparent expolymer particles and fluorimetric measurements that were applied in order to assess the photo-physiological state of the phytoplankton assemblages with respect to their species composition and water column structure (hydrology). The photosynthetic parameters (derived from P–I relationships) and integrated primary production (range 6–644 mg m−2 d−1) responded greatly to the diverse DCM identified and thereby the spatial variability of the primary production observed in the region was found to depend upon the occurrence of the different types of phytoplankton accumulations, which were themselves indicative of the previous history of the water column. The net contribution of the primary production to the air–sea CO2 exchange process was also evaluated in the area. Results indicated that this region behaved as a net sink for the atmospheric CO2, with the intensity of the flux being strongly modulated by the wind intensity. 相似文献