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21.
Rouaida Trabelsi Moncef Zaïri Habib Smida Hamed Ben Dhia 《Comptes Rendus Geoscience》2005,337(5):515-524
The intensive agricultural and economic activities induce the increase of the risk of groundwater quality degradation through high groundwater pumping rates. The salinization and contamination are the main sources of this pollution, especially in coastal aquifers. The explanation of the origin of salinity for the shallow aquifer of Northern Sahel of Sfax was analysed by a chemical study of the groundwater main compounds. The partitioning of groundwaters into homogenous groups is undertaken by graphical techniques, including a Stiff pattern diagram, an expanded Durov diagram and several binary diagrams. The study indicates the presence of various salinization processes. In the recharge area, salinization is the result of dissolution/precipitation of the aquifer formation material (group I). The irrigation water return and the intensive pumping have been identified as major sources of salinization in the south by direct cation exchange and mixing reactions (groups II and III). The anomaly of high groundwater salinity observed near the Hazeg zone was explained by the presence of a seawater intrusion in this area. This hypothesis is related to the high chloride concentration, to the presence of inverse cation exchange reactions (group IV), and to the piezometric level inferior to sea level. To cite this article: R. Trabelsi et al., C. R. Geoscience 337 (2005). 相似文献
22.
Dorra Tanfous Amri Mourad Bédir Mohamed Soussi Hajer Azaiez Lahoussine Zitouni M. Hédi Inoubli Kamel Ben Boubaker 《Comptes Rendus Geoscience》2005,337(7):703-711
Seismic and sequence stratigraphy analyses, petroleum-well control and surface data studies of the Majoura–El Hfay region in the Central Atlas of Tunisia had led to identify and calibrate Jurassic seismic horizons. Seismic stratigraphic sections, seismic tectonics analyses, isochron and isopach mapping of Jurassic sequences show a differentiated structuring of platform and depocentre blocks limited by deep-seated NE–SW, north–south east–west and NW–SE faults intruded by Upper Triassic salt. The early salt migration seems to have started by the platform fracturing during the Lower Liassic rifting event. These movements are fossilized by thickness variations of Jurassic horizons, aggrading and retrograding onlap and toplap structures between subsiding rim-syncline gutters and high platform flanks intruded by salt pillows and domes. The salt migration is also attested by Middle and Upper Jurassic space depocentre migrations. Around the Majoura–El Hfay study blocks bounded by master faults, Triassic salt have pierced the Cretaceous and Tertiary sedimentary cover in a salt diapir extrusion and salt wall structures. To cite this article: D. Tanfous Amri et al., C. R. Geoscience 337 (2005). 相似文献
23.
Laurence Le Callonnec Alain Person Maurice Renard René Létolle Nathalie Nebout Leila Ben Khelifa Ivan Rubanov 《Comptes Rendus Geoscience》2005,337(12):1035-1044
The withdrawal of the Aral Sea tributaries (Amu and Syr Daria) for cultures has led to significant falls of its level and an important increase in its salinity. During the Holocene, a succession of low and high water inputs occurred. Silty deposits correspond to the high levels and carbonates to the low levels. This study makes a distinction between the Syr Daria and the Amu Daria water inputs during low-level periods by using mineralogical and chemical compositions of the carbonates deposits. Waters from the Syr Daria are more sulphatic and have a low iron content in comparison with that of the Amu Daria. The Syr Daria was the major tributary around 7500, 4956 and 970 yr?BP, whereas around 6200 and 3610 yr?BP, inflow also from the Amu Daria is observed. To cite this article: L. Le Callonnec et al., C. R. Geoscience 337 (2005). 相似文献
24.
WANG Fang HE Yongtao FU Gang NIU Ben ZHANG Haorui LI Meng WANG Zhipeng WANG Xiangtao ZHANG Xianzhou 《资源与生态学报(英文版)》2020,11(3):290-297
Enclosure is one of the most widely used management tools for degraded alpine grassland on the northern Tibetan Plateau, but the responses of different types of grassland to enclosure may vary, and research on these responses can provide a scientific basis for improving ecological conservation. This study took one site for each of three grassland types (alpine meadow, alpine steppe and alpine desert) on the northern Tibetan Plateau as examples, and explored the effects of enclosure on plant and soil nutrients by comparing differences in plant community biomass, leaf-soil nutrient content and their stoichiometry between samples from inside and outside the fence. The results showed that enclosure can significantly increase all aboveground biomass in these three grassland types, but it only increased the 10-20 cm underground biomass in the alpine desert. Enclosure also significantly increased the leaf nutrient content of the dominant plants and contents of total nitrogen (N), total potassium (K), and organic carbon (C) in 10-20 cm soil in alpine desert, thus changing the stoichiometry between C, N and P (phosphorus). However, enclosure significantly increased only the N content of dominant plant leaves in alpine steppe, while other nutrients and stoichiometries of both plant leaves and soil did not show significant differences in alpine meadow and alpine steppe. These results suggested that enclosure has differential effects on these three types of alpine grasslands on the northern Tibetan Plateau, and the alpine desert showed the most active ecological conservation in the responses of its soil and plant nutrients. 相似文献
25.
Intensification of Southern Hemisphere westerly winds 2000–1000 years ago: evidence from the subantarctic Campbell and Auckland Islands (52–50°S) 下载免费PDF全文
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