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11.
R. Hadj Amor G. Quaranta F. Gueddari D. Million N. Clauer 《Environmental Geology》2008,54(5):1103-1110
The life cycle impact assessment (LCIA) is a standard tool for the study of the environmental impact on a system including
all activities in connection with manufacturing a product or detailing a service, from extraction of raw materials to disposal
of final waste. Here, the system is not only anthropogenic, but also includes both natural behaviours and pollution aspects
from human activity: it is a coastal lagoon with varied activities and waste disposals nearby. This stagnant zone is highly
subjected to solar exposure and tends to dryness during summer, thus offering ideal conditions to algal proliferation. We
have taken into account the trophic state of the lagoon assessed by the LCIA methodology, on the basis of the aquatic eutrophication
potential (AEP). We have considered the concentrations of the phosphorus and nitrogen compounds for the calculation of the
AEP and their spatial and temporal variations in the lagoon. The results show that the AEP of the phosphorus exceeds systematically
the AEP of nitrogen and that the contents of both are systematically higher in summer than in winter. Nitrogen is the limiting
factor for the algae growth. Ammonia and phosphates are the most important nutrients for the AEP in summer, whereas nitrates
dominate in winter. In addition, the spatial and temporal variations of the N and P nutrients of the surface waters allow
to distinguish three areas in the lagoon: a transition zone between the sea- and the lagoon waters; a zone reflecting directly
the influence of the O. Bey creek- and the treated-waste waters and one representing the most isolated part of the lagoon
and consequently the less contaminated by nutrient inputs. 相似文献
12.
Salah Abdesselam Amor Halitim Anthony Jan Fabienne Trolard Guilhem Bourrié 《Environmental Earth Sciences》2013,70(5):2129-2141
In southern Hodna, an arid region of Algeria, the extension of irrigated agriculture and overexploitation of groundwaters have led to a rupture with traditional land use by pastoralism. Due to the arid conditions, groundwaters are the only water resources for man and irrigation. This study focuses on nitrate contamination of groundwaters and its increase since the last 40 years, on the basis of two archives and recent analyses. The chemical facies of waters is sulphate-chloride, the risk of salinity is moderate to large. The sodicity risk, as estimated by the SAR, is low due to the large salinity and the sandy soil texture. Nitrate contamination of deep groundwater is a clear evidence when recent data are compared to the historical data. From 1996 to 2008, the proportion of samples with NO 3 ? concentrations larger than 50 mg/L increases from 24 to 61 %, the proportion of samples with NO 3 ? concentrations larger than 100 mg/L increases from 12 to 27 %. The study points at a general contamination of aquifers from anthropic origin: phreatic water was already contaminated when pastoralism was dominant (1967); as population increased and irrigation agriculture developed with large use of N-fertilizers and organic amendments, contamination extended spatially and vertically to deep aquifer. To remediate this contamination, fertilizers should be fractionated and limited to plant requirements on the basis of soil and plant analyses. Excess of irrigation should be avoided. Soil surface should be continuously covered to prevent nitrate leaching. Secondly, more efficient irrigation techniques, such as localized irrigation, should be implemented, with adaptation of crop systems and fertilizer inputs to arid conditions. Farmers should then be trained; simultaneously, local agronomic references that are presently lacking should be acquired. 相似文献
13.
Montserrat Bóo Margarita Amor 《International journal of geographical information science》2013,27(4):417-439
Hybrid digital terrain models combine terrain data with different topologies and resolutions. Cartographic digital terrain models are typically composed of regular grid data that can be locally refined by adding a Triangulated Irregular Network (TIN) that represents morphologically complex terrain parts. Direct rendering of both datasets to visualize the digital terrain model generates discontinuities, as the meshes are disconnected. The utilization of complete/partial precomputed tessellation solutions solves the problem of quality, but limits the applicability of the representation to models with a fixed relative position between datasets. In this paper, we present a new scheme for hybrid terrain representation that permits the dynamic generation of the adaptive tessellation required to join the grid and TIN models. Our proposal permits the dynamic modification of the relative position between datasets. This increases the representation capabilities for those applications where this property is interesting as, for example, urban and landscape planning applications. The algorithm we propose is based on the identification of convex areas on the TIN and the efficient generation of triangles to join the models based on this convex structure. As a result, high quality models without discontinuities are obtained, increasing the flexibility of previous solutions based on fixed precomputations. 相似文献
14.
E.G. Paredes M. Bóo M. Amor J.D. Bruguera J. Döllner 《International journal of geographical information science》2013,27(5):771-793
Hybrid terrains are a convenient approach for the representation of digital terrain models, integrating heterogeneous data from different sources. In this article, we present a general, efficient scheme for achieving interactive level-of-detail rendering of hybrid terrain models, without the need for a costly preprocessing or resampling of the original data. The presented method works with hybrid digital terrains combining regular grid data and local high-resolution triangulated irregular networks. Since grid and triangulated irregular network data may belong to different datasets, a straightforward combination of both geometries would lead to meshes with holes and overlapping triangles. Our method generates a single multiresolution model integrating the different parts in a coherent way, by performing an adaptive tessellation of the region between their boundaries. Hence, our solution is one of the few existing approaches for integrating different multiresolution algorithms within the same terrain model, achieving a simple interactive rendering of complex hybrid terrains. 相似文献
15.
Extraction of information content from stochastic disaggregation and bias corrected downscaled precipitation variables for crop simulation 总被引：3，自引：3，他引：0
Ashok K. Mishra Amor V. M. Ines Vijay P. Singh James W. Hansen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(2):449-457
We applied a simple statistical downscaling procedure for transforming daily global climate model (GCM) rainfall to the scale of an agricultural experimental station in Katumani, Kenya. The transformation made was two-fold. First, we corrected the rainfall frequency bias of the climate model by truncating its daily rainfall cumulative distribution into the station’s distribution based on a prescribed observed wet-day threshold. Then, we corrected the climate model rainfall intensity bias by mapping its truncated rainfall distribution into the station’s truncated distribution. Further improvements were made to the bias corrected GCM rainfall by linking it with a stochastic disaggregation scheme to correct the time structure problem inherent with daily GCM rainfall. Results of the simple and hybridized GCM downscaled precipitation variables (total, probability of occurrence, intensity and dry spell length) were linked with a crop model for a more objective evaluation of their performance using a non-linear measure based on mutual information based on entropy. This study is useful for the identification of both suitable downscaling technique as well as the effective precipitation variables for forecasting crop yields using GCM’s outputs which can be useful for addressing food security problems beforehand in critical basins around the world. 相似文献
16.
17.
Souad Zarrouk Alexander V. Ereskovsky Karim Ben Mustapha Amor El Abed Thierry Pérez 《Marine Ecology》2013,34(4):432-442
The study of the reproductive processes of benthic invertebrates is essential to the understanding of their population dynamics and is also important in formulating conservation plans, especially for exploited species. The sexual reproduction of Hippospongia communis, the ‘honeycomb’ bath sponge, was studied at two locations in the Mediterranean Sea: the Kerkennah Islands (Tunisia, South Mediterranean), where the mean annual seawater temperature is 19 °C, and Marseille (France, Northwestern Mediterranean Sea), where the mean annual water temperature is 16 °C. The aim of this comparative study was to determine whether different environmental conditions could affect reproduction patterns. At both locations, H. communis was found to contain sexual reproductive elements year‐round. Oogenesis and embryogenesis occurred throughout the year, whereas spermatogenesis occurred during shorter periods between October and November, in both populations. While gametogenesis seemed to be synchronized, indicating that fertilization could occur at the same time at both locations, spawning was observed in late summer in Marseille, whereas it started in late spring for the Kerkennah population. Larval development of H. communis seems to take longer for sponges living at cooler locations such as Marseille. Reproductive effort calculated for both sexes showed significantly higher values for specimens from Kerkennah Islands. By comparing sexual reproductive patterns of populations living in two contrasted environments, we suggest that a change of thermal regime can affect H. communis phenology. 相似文献
18.
Hanen Azaza Lassaad Mechi Amira Doggaz Virgil Optasanu Mohamed Tlili Mohamed Ben Amor 《Arabian Journal of Geosciences》2017,10(10):220
During the production of hydrocarbons from subterranean reservoirs, scaling with calcium carbonate and barium sulfate causes flux decline and dangerous problems in production facilities. This work is intended to study the effect of calcium ions on the precipitation of barium sulfate (barite); then, the effect of the formed barite on calcium carbonate crystallization. The conductometric and pH methods were used to follow the progress of the precipitation reaction in aqueous medium. The obtained precipitates were characterized by FTIR, RAMAN, SEM, and XRD. It was shown that Ca2+ in the reaction media does not affect the microstructure of barite even for higher calcium–barium molar ratio. It influences the precipitation kinetics and the solubility of barite by the formation of CaSO4° ion pairing as a predominant role of complex formation (CaSO4) and the increase of the ionic strength. In Ca(HCO3)2-BaSO4-NaCl aqueous system, experiments have showed that added or formed barite in the reaction media accelerates calcite precipitation. No effect on the microstructure of heterogeneous formed calcite which remain calcite shape. However the presence of carbonate ions affects slightly the microstructure of barite. 相似文献
19.
The present investigation is concerned with the identification of diagnostic lithogeochemical alteration signatures around volcanic-exhalative massive sulfide deposits in the Superior Province, with the overall objective of deriving lithogeochemical criteria, applicable in the search for new deposits of this type.Previous work on these deposits has indicated that, in general, the footwall alteration halo is marked by iron and magnesium enrichment, and calcium and sodium depletion. These features are often only detectable if the over-riding effects of igneous differentiation are compensated. It is apparent that the relative contribution of individual elements to the geochemical alteration varies from deposit to deposit, preventing the recognition of any universal geochemical alteration criterion.The role of discriminant analysis has been examined to establish the possibility of the technique indicating a more reliable expression of geochemical alteration. Discriminant analysis establishes the optimum weighted combination of variables to distinguish two or more populations from each other, in this case mineralized from barren environments. The application of the procedure to the data relating to the composition of wall rock associated with eight volcanic-exhalative massive sulfide deposits has drawn attention to the existence of two distinct types of alteration. The Joutel and Poirier deposits are characterized by Fe2O3, MgO, Zn and Ag enrichment, and CaO and Na2O depletion; this alteration style has been termed the “Joutel” type. At the South Bay, Sturgeon Lake and Mobrun deposits, Na2O is also strongly depleted, but Fe2O3 and MgO are usually depleted and K2O is strongly enriched; this alteration style has been termed the “South Bay” type. Both of these alteration styles are displayed at the Mattabi and East Waite deposits. “Joutel” type alteration appears to be in close spatial association with discharge vents, while “South Bay” alteration is more laterally widespread and is representative of at least one deposit thought to be formed distally from its associated discharge vent.These geochemical signatures are more strongly expressed in pyroclastic rocks, and andesites, relative to massive rocks, and rhyolites.The geochemical alteration patterns delineated in this way constitute significantly larger exploration targets than the readily observable mineralogical alteration haloes.Results of the current investigations indicate that the mineralizing processes associated with Archean volcanic-exhalative massive sulfide deposits have given rise to more than oversimplification to aim exploration at the detection of a single type of response. The application of discriminant analysis provides a potential means of identifying and comparing as many responses as are present at the deposits studied. In this respect it is superior to any univariate statistical method, and has considerable application in exploration. 相似文献
20.
The littoral fringe ranging between the capes of Bizerte and Ras Ettarf (north-eastern of Tunisia) represents an unstable
and complex system of the Tunisian littoral. The instability of this zone is dependent, on one hand, on natural phenomena
contributing to the destabilization of certain sectors to which are added the induced effects of anthropic factors on the
other hand. This study was carried out from grain size analysis and a simulation of swell plans. This led the authors to highlight
the increasing grain size classification from the zones of the Capes towards the sandy low coasts and to quantify the moved
volumes under the effect of the dominant swells in order to simulate the fattening and erosion zones in this sector. A littoral
transit of direction north–south is able to transport 45,000 m3/year of sediment which are participating in the fattening of the beach of Sidi Salem; 6,000 m3/year of sandy sediments are directed towards the beach of R'mel and 12,000 m3/year are participating in the fattening of the beaches of Chatt Mami (Ras Jebel) and Lahmmari (Raf Raf). 相似文献