排序方式： 共有43条查询结果，搜索用时 781 毫秒
11.
Hajer Ferchichi Boutheina Farhat Mohamed F. Ben-Hamouda Abdallah Ben-Mammou 《Arabian Journal of Geosciences》2017,10(23):530
The rapid urbanization and industrialization of the Manouba plain (Northeastern Tunisia), the extensive agricultural expansion and the succession of dry years during recent decades have exerted greatly load on the water needs and lead to groundwater quality degradation. The aim of this study is to evaluate the processes controlling the groundwater mineralization of the shallow aquifer for determining its suitability for drinking and agricultural purposes. For establishing that, we combine several geological, hydrological and hydrochemical data with geostatistical techniques. The samples were collected at 17 sites covering 230 km2 of the study area and analyzed for major and trace components. The total dissolved solid (TDS) content ranges from 1372 to 3999 mg/l. The results of Piper diagram indicate that Na+/Cl? and Ca2+?>?Na+/SO4 2? were the main dominant water types localized in the sloping sides of the watershed and near the saline depression; the suitability for irrigation use was also evaluated. The high concentrations of nitrates and chlorides are indicators of anthropogenic pollution, like the agricultural over application of nitrogen fertilizers and the discharge of domestic and industrial wastewater. Saturation indexes calculated by using PHREEQC (USGS) program show that groundwaters are undersaturated with evaporitic minerals (halite, gypsum) and saturated with carbonates (calcite, aragonite). The use of principal component analysis and hierarchical cluster analysis has shown that two main factors accounting 67.13% of the information of variability within the dataset confirm the existence of dissolution of evaporitic minerals and the mechanisms of nitrate increasing the salinity of the Manouba groundwater. 相似文献
12.
Farhat?AbbasEmail author Iqra?Rehman Muhammad?Adrees Muhammad?Ibrahim Farhan?Saleem Shafaqat?Ali Muhammad?Rizwan Muhammad?Raza?Salik 《Theoretical and Applied Climatology》2018,131(3-4):1101-1117
This study examines the variability and change in the patterns of climatic extremes experienced in Indus-Delta of Sindh province of Pakistan, comprising regions of Karachi, Badin, Mohenjodaro, and Rohri. The homogenized daily minimum and maximum temperature and precipitation data for a 36-year period were used to calculate 13 and 11 indices of temperature and precipitation extremes with the help of RClimDex, a program written in the statistical software package R. A non-parametric Mann–Kendall test and Sen’s slope estimates were used to determine the statistical significance and magnitude of the calculated trend. Temperatures of summer days and tropical nights increased in the region with overall significant warming trends for monthly maximum temperature as well as for warm days and nights reflecting dry conditions in the study area. The warm extremes and nighttime temperature indices showed greater trends than cold extremes and daytime indices depicting an overall warming trends in the Delta. Historic decrease in the acreage of major crops and over 33% decrease in agriculture credit for Sindh are the indicators of adverse impacts of warmer and drier weather on Sindh agriculture. Trends reported for Karachi and Badin are expected to decrease rice cultivation, hatching of fisheries, and mangroves forest surrounding these cities. Increase in the prevailing temperature trends will lead to increasingly hotter and drier summers resulting to constraints on cotton, wheat, and rice yield in Rohri and Mohenjodaro areas due to increased crop water requirements that may be met with additional groundwater pumping; nonetheless, the depleted groundwater resources would have a direct impact on the region’s economy. 相似文献
13.
Wet processing of natural phosphate to increase the P2O5 content and eliminate non-desired fraction (both coarse and fine fractions) took place in various laundries of the Gafsa-phosphatic area. Effluents of those laundries often contain various contaminants that are directly discharged to the receiving waterbody, representing a serious threat to the environment. Physico-chemical characterization of those effluents showed elevated levels of sulfates, fluorine, and metals. The bordering land showed gypseous soils. Those soils are covered by the discharged phosphate-washing sludge. The effect of which on the structure and the permeability of the soils seemed to be significantly harmful. Batch tests were conducted to evaluate the mobility of various metals on the surrounding area of phosphate laundries. Leaching results revealed low cadmium and uranium mobilities. However, Cd concentrations in the studied samples leached from soils exceeded the standards. This suggested the contamination by cadmium. 相似文献
14.
M. Rafique M. H. Rathore 《International Journal of Environmental Science and Technology》2013,10(5):1083-1090
Extensive export quality reserves of granite, dolerite and marbles which are used for interior decorations as wall facing, paving floors, kitchen counter tops, etc., are available in Azad Kashmir. Since these stones contain radium in trace amounts, therefore, its use as a building material may be a potential source of indoor radon. In order to assess health hazards due to the use of these stones as a building material, samples were collected from different mining sites. After processing, these samples were placed in plastic containers and box type radon detectors were installed in it at the height of 25 cm above the surface of the samples. The containers were then hermetically sealed. After 60 days of exposure to radon, CR-39 detectors were etched in 6 M NaOH at 70 °C for 9 h and measured track densities were related to radon concentration. Radon exhalation rate form the studied granites, marble and dolerite samples varied from 87 ± 26 to 353 ± 36 mBq m?2h?1, 79 ± 25 to 650 ± 42 mBq m?2h?1 and 90 ± 26 to 324 ± 36 mBq m?2h?1, respectively. These decorative stones are therefore used in buildings and for export purposes as the observed radon exhalation values are smaller than that of the EPA recommended-action level. 相似文献
15.
Résumé Cette étude est basée sur l'analyse des données gravimétriques; elle a pour but d'améliorer la connaissance de la structure de la plaine de Mornag. La carte de l'anomalie résiduelle a d'abord été calculée à partir de la carte de l'anomalie de Bouguer en enlevant un gradient régional. La résiduelle calculée fournit des informations sur la variation de la densité dans le bassin de Mornag. Afin de mettre en évidence les différentes structures dans le bassin, nous avons calculé la magnitude du gradient horizontal (MGH). Cette technique a permis de déterminer des linéaments gravimétriques représentant l'emplacement des contrastes de densité, et de déduire une carte structurale de la zone d'étude. Cette carte constitue un document très utile pour orienter l'exploration des ressources en eau dans la plaine de Mornag. Citation Farhat, B., Benassi, R., Jallouli, C. & Ben Mammou, A. (2010) Contribution de la gravimétrie à l'étude de la structure de la plaine de Mornag (nord est de la Tunisie): implications hydrogéologiques. Hydrol. Sci. J. 55(8), 1396–1404. 相似文献
16.
ASHRAF Sobia ABBAS Farhat IBRAHIM Muhammad RASHID Umer KHALID Shoaib Raza AHMAD Hammad Rehman HAKEEM Khalid MAJEED Tahir 《地理学报(英文版)》2015,25(2):225-235
Groundwater is the most appropriate and widely used source of drinking water, which is increasingly threatened by pollution from industrial and agricultural activities. To check the severity of the problem, 156 groundwater samples were collected from various depths (60-110 ft) of 52 different localities in Faisalabad city, the third largest metropolis in Pakistan, and analyzed for the metals (Zn, Cu, Cd, Ni, Pb, Mn and Fe) concentration in 2009. Quantification was done by using Flame Atomic Absorption Spectrophotometer technique and the results were compared with WHO standards for drinking water quality. Results showed that the levels of Cu, Mn and Fe were below the WHO standards while the concentrations of Zn, Cd, Ni and Pb were above the recommended levels of safe drinking water. Correlation analysis among the occurrence of these heavy metals revealed a highly significant and positive correlation of Mn with Zn and Fe. A significant and positive correlation of Cd was also found with Cu and groundwater depth showing that there is strong association between Cu-Cd pair and that the Cd concentration varies with depth of groundwater in the study area. Regional patterns of heavy metals occurrence were mapped using Geographical Information System (GIS) for the identification and demarcation of risk areas. The concentration maps may be used by policymakers of the city to mitigate groundwater pollution. 相似文献
17.
18.
Kyle P.Larson Asghar Ali Sudip Shrestha Mathieu Soret John M.Cottle Rafique Ahmad 《地学前缘(英文版)》2019,10(3):849-861
New metamorphic petrology and geochronology from the Loe Sar dome in the Swat region of northern Pakistan place refined constraints on the pressure, temperature and timing of metamorphism and deformation in that part of the Himalayan orogen. Thermodynamic modelling and monazite petrochronology indicate that metamorphism in the area followed a prograde evolution from ～525 ± 25 ℃and 6 士 0.5 kbar to ～610 ± 25 ℃ and 9 士 0.5 kbar, between ca. 39 Ma and 28 Ma. Partitioning of heavy rare earth elements between garnet rims and 30-28 Ma monazite are interpreted to indicate coeval crystallization at peak conditions. Microtextural relationships indicate that garnet rim growth post-dated the development of the main foliation in the area. The regional foliation is folded about large-scale N-S trending fold axes and overprinting E-W trending folds to form km-scale domal culminations. The textural relationships observed indicate that final dome development must be younger than the 30-28 Ma monazite that grew with garnet rims post-regional foliation development, but pre-doming-related deformation. This new timing constraint helps resolve discrepancy between previous interpretations,which have alternately suggested that N-S trending regional folds must be either pre-or post-early Oligocene. Finally, when combined with existing hornblende and white mica cooling ages, these new data indicate that the study area was exhumed rapidly following peak metamorphism. 相似文献
19.
H. Ferchichi M. F. Ben Hamouda B. Farhat A. Ben Mammou 《International Journal of Environmental Science and Technology》2018,15(11):2473-2492
The integration of the statistical approaches and GIS tools with the hydrogeological and geological contexts allowed the assessment of the processes that cause groundwater quality deterioration in the great important deltaic aquifer in the northeastern Tunisia (Medjerda Lower Valley Aquifer). The spatial variation of the groundwater parameters and the molar ratio (Cl?/Br?) were also used to determine the possible impacts from seawater intrusion and from the septic tank leachate. Sixty shallow groundwater samples were collected in 2014 and analyzed for major and trace ions over an area of about 1090 km2 to determine the suitability for drinking or agricultural purposes. The total dissolved solids (TDS) content ranges from 1005 to 19,254 mgl?1 with a mean value of 3477.18 mgl?1. The chemistry is dominated by the sodium–chloride waters (55%). Mapping of TDS, Cl?, Na+, SO42? and NO3? using kriging method shows a clear increase in salinity toward the coastline accompanied by Na+ and Cl? increase which may be related to seawater intrusion and halite dissolution. Locally, higher nitrate concentration is related to the agricultural activities inducing contribution of chemical fertilizers and irrigation with treated wastewater. The saturation indices indicate that all carbonate minerals tend to reach saturation equilibrium confirming water–rock interactions, while evaporitic minerals are still in sub-saturation state and may increase the salinity of the groundwater. The principal component analysis proves the occurrence of groundwater contamination principally by seawater intrusion in the factor I (74.15%) and secondary by an anthropogenic source in the factor II (10.35%). 相似文献
20.
Acta Geotechnica - This paper is devoted to study the elastic–plastic damage behavior of heterogeneous shale rocks. The representative microstructure of this kind of rocks is first studied in... 相似文献