Residue of methanolic extract of Egyptian Jatropha curcas contains bioactive substances such as phenolic compounds, which succeeded to be used as natural antioxidants for the protection of oils and their corresponding biodiesel against oxidative deterioration. In the present work, the residue of Jatropha roots were extracted with methanol and resulting residues, were investigated regarding their content of total phenolic compounds by folin-Cioalteau assay. Further, the antioxidant activities of the extracts were characterized by the 2,2-diphenyl-1-picrylhydrazyl radical method and proved remarkable results. Oxidation stability of Jatropha oil, used fried oil and olive oil and their corresponding biodiesel obtained by conventional transesterification were tested using thermal oxidation. Natural antioxidants such as (α-trocopherol), synthetic antioxidants as butylated hydroxytoluene and natural Jatropha root extract were used in the present study in comparison to investigate their addition effect on the oxidative stability of oils and their corresponding biodiesel. In the rapied thermal treatment test, results showed that addition of butylated hydroxytoluene 0.25 % was able to stabilize Jatropha oil 6 h, but poorly stabiliz biodiesel. Addition of 0.25 % α-trocopherol to Jatropha oil showed less oxidation stability after 2 h thermal treatment. Crude root extract addition at 0.25% to Jatropha oil showed good stability up to 4 h thermal treatment while addition of root extract at 0.25 % to biodiesel showed better stability up to 6 h thermal treatment. Besides addition of 220 ppm crude root extract to biodiesel was enough sufficient to occure oxidative stabilization. Also Jatropha root residue addition at 400 ppm was effective antioxidant for fresh Jatropha oil. 相似文献
The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area. 相似文献
This paper investigates spatial variability of temperature trends over Libya in the second half of the 20th century. The study is based on complete and homogeneous time series of minimum, maximum, and mean temperature for ten observatories. During the investigated period (1951–1999), temperature trend analyses have experienced a downward trend in the maximum surface temperature (about –0.06°C decade–1) and an upward trend in the minimum surface temperature (about 0.23°C decade–1). Cooling tendency in maximum temperature is spatially more pronounced in inland stations compared to coastal stations. At the seasonal scale, maximum temperature cooling is more obvious in winter and spring, meanwhile minimum temperature warming is more pronounced in summer and fall. In accordance with global trends, the surface mean temperature has moderately risen at an average rate of 0.09°C decade–1. However, this trend has shown considerable temporal variability considering a more pronounced upward trend in summer and fall. In conjunction with other regional and global investigations, clear trends towards smaller diurnal range are presented (–0.28°C decade–1). 相似文献
In the current study, an integration of Enhanced Thematic Mapper Plus (ETM+), field, and laboratory data have been used for lithological mapping of different granitic phases in the Kadabora area, Eastern Desert, Egypt. Application of enhancement techniques, including a new proposed band ratio combination (ratio 5/3, 3/1, 7/5 in RGB, respectively) and supervised classification images are used in discriminating different granitic phases in the Kadabora pluton from each other and from their environs. The data have been proved with the help of field and geochemical investigations. The results revealed that: (1) the Kadabora granitic pluton could be distinguished into three phases that recognized by field and laboratory investigation including granodiorite (phase I), monzogranite (phase II), and syeno-alkali feldspar granite (phase III). These phases are arranged according to their relative ages while the country rocks include ophiolitic mélange and metagabbro–diorite complex. It is also confirmed that the granitic pluton is invaded by dyke swarms which is trending in N–S direction. Geochemically, results show that the granodiorite is calc-alkaline, I-type and formed under subduction tectonic regime. Monzogranite falls within the alkaline and highly fractionated calc-alkaline granites, whereas syeno-alkali feldspar granite extends into proper alkaline granitoids field. Monzogranite and syeno-alkali feldspar granite belong to the A2-subtype granite. This A2-subtype granite was probably formed in an extensional regime, subsequent to subduction which can lead to tensional break-up of the crust (i.e., post-collisional, post-orogenic granites). The monzogranite and the syeno-alkali feldspar granite were probably formed by partial melting of relatively anhydrous lower crust source and/or tonalite to granodiorite is viable alternative to the granulite source. 相似文献
The paper presents results of a laboratory experimental program performed on limestone rock samples, using both physical and mechanical methods. The studied rocks (Simsima Formation, Upper Cretaceous) can be classified as highly ferruginous and highly fossilliferous limestone. The lower part of the Simsima Formation contains common fauna such as Orbittoids, rhodolithic and rudists, whereas the upper part of the limestone is interbedded with conglomerates. Detailed geological, petrographic in addition to physical and mechanical tests were carried out on some representative samples from the Faiyah area, aiming at getting a better understanding of the important properties of these rocks. It is shown that the uniaxial unconfined compressive stress is the controlling factor of classification of the Faiyah limestone. 相似文献
A density-dependent numerical groundwater model was applied to study the climate change impact in a shallow aquifer in the Mediterranean coast of Morocco, the Saïdia aquifer. The stresses imposed to the model were derived from the IPCC emission scenarios and included recharge variation and sea level rise. The main effect of the climate change in the Saïdia aquifer will be a decrease in renewable resources, which in the worst-case scenario may decrease to 50–60% of present-day values, due to the decline in recharge and to a reduced inflow from the adjacent Triffa aquifer. The water quality will be affected mostly in the area immediately adjacent to the seashore, where salinity may increase up to 30 g/l. Localised areas may see a decrease in salinity due to the induced freshwater recharge from Oued Moulouya River and diminished inflow from high-salinity springs. 相似文献
Future climate projections of extreme events can help forewarn society of high-impact events and allow the development of better adaptation strategies. In this study a non-stationary model for Generalized Extreme Value (GEV) distributions is used to analyze the trend in extreme temperatures in the context of a changing climate and compare it with the trend in average temperatures.
The analysis is performed using the climate projections of the Canadian Regional Climate Model (CRCM), under an IPCC SRES A2 greenhouse gas emissions scenario, over North America. Annual extremes in daily minimum and maximum temperatures are analyzed. Significant positive trends for the location parameter of the GEV distribution are found, indicating an expected increase in extreme temperature values. The scale parameter of the GEV distribution, on the other hand, reveals a decrease in the variability of temperature extremes in some continental regions. Trends in the annual minimum and maximum temperatures are compared with trends in average winter and summer temperatures, respectively. In some regions, extreme temperatures exhibit a significantly larger increase than the seasonal average temperatures.
The CRCM projections are compared with those of its driving model and framed in the context of the Coupled Model Intercomparison Project, phase 3 (CMIP3) Global Climate Model projections. This enables us to establish the CRCM position within the CMIP3 climate projection uncertainty range. The CRCM is validated against the HadEX2 dataset in order to assess the CRCM representation of temperature extremes in the present climate. The validation is also framed in the context of CMIP3 validation results. The CRCM cold extremes validate better and are closer to the driving model and CMIP3 projections than the hot extremes. 相似文献
Severe weather has important social and economic impacts. Some studies have indicated that its intensity may increase over this century as a consequence of climate change induced by greenhouse gases. This study aims to investigate the possibility of a future increase in deep convective events over North America resulting from the evolution of favourable atmospheric conditions. Our analysis is based on an ensemble of projections performed using the Canadian Regional Climate Model (CRCM) at 45?km resolution, driven by different Global Climate Models (GCMs) and reanalyses. We concentrate our study on Convective Available Potential Energy (CAPE), vertical wind shear, and convective precipitation. Based on two different approaches to linking atmospheric conditions and severe weather, we find that the number of extreme weather events is expected to increase during the twenty-first century. In agreement with other studies on this subject, we find that CAPE is expected to increase, whereas wind shear is expected to decrease slightly. Through the analysis of the CRCM's convective precipitation outputs, we show that severe convective liquid precipitation events may become both more frequent and slightly more intense. Sensitivity experiments show that results depend on the driving GCM although they confirm the general conclusions. Additional experiments conducted with reduced humidity input at the lateral boundaries show the significant role that the humidity level of the driving GCMs has on simulated extreme regional events. At the regional level results are, in general, consistent with those found at the continental scale, but large inter-regional variations exist. 相似文献
The Carboniferous carbonates of the Um Bogma Formation of the west-central Sinai include two rock successions. The lower succesion consists of karstic carbonates, intrakarstic products, weathering varieties, manganese deposits, and soil cover. The lower karstic rocks and the associated soil cover are preserved under a rhythmic alternation of dolostone and shale forming the upper rock succession of the Um Bogma Formation. The all over congruent relations between the manganese deposits and the fossilized karst profile, karst products, and the associated pedogenesis demonstrate the role of weathering in the accumulation of these deposits during Carboniferous karstification. It is clear that the manganese oxides were deposited during the mature stage of Carboniferous karstification, i.e., during the soil formation, preceeding initial diagenetic change of the karstic rocks and final deposition of the related late-diagenetic caliche cement. The geochemical behavior of Mn during the karstification and the microbiological processes involved in pedogenesis played an essential role in the concentration of the manganese ore in the subsoil horizon of the paleokarst profile. The Um Bogma Formation has been subjected to another episode of karstification during the Quaternary and resulted in lowering of the landforms of the Carboniferous carbonates and destruction of the Carboniferous karst and the associated manganese deposits in some localities. 相似文献