排序方式: 共有162条查询结果,搜索用时 46 毫秒
41.
Samira Akhavan Sayed-Farhad Mousavi Jahangir Abedi-Koupai Karim C. Abbaspour 《Environmental Earth Sciences》2011,63(6):1155-1167
One of the major causes of groundwater pollution in Hamadan–Bahar aquifer in western Iran is a non-point source pollution
resulting from agricultural activities. Withdrawal of over 88% of drinking water from groundwater resources, adds urgency
to the studies leading to a better management of water supplies in this region. In this study, the DRASTIC model was used
to construct groundwater vulnerability maps based on the “intrinsic” (natural conditions) and “specific” (including management)
concepts. As DRASTIC has drawbacks to simulate specific contaminants, we conditioned the rates on measured nitrate data and
optimized the weights of the specific model to obtain a nitrate vulnerability map for the region. The performance of the conditioned
DRASTIC model improved significantly (R
2 = 0.52) over the intrinsic (R
2 = 0.12) and specific (R
2 = 0.19) models in predicting the groundwater nitrate concentration. Our study suggests that a locally conditioned DRASTIC
model is an effective tool for predicting the region’s vulnerability to nitrate pollution. In addition, comparison of groundwater
tables between two periods 30 years apart indicated a drawdown of around 50 m in the central plain of the Hamadan–Bahar region.
Our interpretation of the vulnerability maps for the two periods showed a polluted zone developing in the central valley requiring
careful evaluation and monitoring. 相似文献
42.
R.A. Feagin J.L. Irish I. Möller A.M. Williams R.J. Colón-Rivera M.E. Mousavi 《Coastal Engineering》2011
This technical note presents empirically-derived values for biophysical attributes of several commonly occurring wetland plant species, including plant stem diameter and tapering, plant clump and stem spacing statistics, biomass, Young's modulus of elasticity, and bending strength. These parameters can be used to more realistically configure plant canopies in numerical and laboratory studies to further our understanding of wave attenuation by wetlands. 相似文献
43.
Emad Ghaleh Noei Mahdi Hasanlou Mohammad Ali Sharifi 《Journal of the Indian Society of Remote Sensing》2018,46(12):2093-2106
Seafloor topography certainly has an impact on ocean circulation in different ways. Due to this assumption, the sea surface currents calculated by optical flow (Horn–Schunck) and geostrophic currents methods are analyzed to observe this impact. Pair of sea surface temperature imageries, calculated sea surface height and sea level anomaly are showed beside depth map in areas with meaningful bathymetric features such as underwater mountains and pools. The reason for the formation of some eddies in the Caspian Sea and Indian Ocean is concluded from the location of pools and knolls. In this study, in addition to introducing new time span for calculating geostrophic currents, Ocean Surface Current Analyses Real-Time (OSCAR) currents are applied to validate our estimated currents. Variety of products such as sea surface temperature imageries, OSCAR currents, depth map, calculated results like sea level anomaly and absolute dynamic topography and estimated currents via optical flow and geostrophic currents have been collected in this paper to make very detailed investigation on depth effect on mentioned water parameters. Results show that impacts of knolls and pools are meaningfully clear in optical flow and geostrophic currents in shaping and rationing water motions. 相似文献
44.
Parkachik Glacier is located in the Suru sub-basin of the Upper Indus River, Zanskar Himalaya. The Glacier has been analysed using Corona KH-4B (1971), Landsat-TM (1999), field survey (2015), Google EarthTM (2015) and ASTER GDEM (2015) for frontal recession and area changes. Overall, from 1971 to 2015, the Glacier has retreated by 127 ± 0.09 m i.e. (0.75 ± 0.07%) at a rate of 2.9 ± 0.004 ma?1 with a simultaneous decrease in area from 49.5 to 48.8 km2 i.e. 740 ± 0.7 m2 (1.5 ± 0.09%) at a rate of 74 ± 0.7 m2a?1. However, during recent decade (1999–2015), the rate of glacier recession of 3.9 ± 0.004 ma?1 with a corresponding area loss of 500 ± 0.74m2 (1 ± 0.1%) was higher than the retreat rate of 2.3 ± 0.001 ma?1 and an area loss of 240 ± 0.02m2 (0.48 ± 0.08%) during 1971–1999. In the field, the evidences of glacier recession are present in the form of separated dead ice blocks from the main Glacier, recessional dumps/moraines, active ice calving activity and a small proglacial pond/lake at the terminus/snout of the Glacier. However, the recession over the studied period has been very slow and is controlled by its topographic configuration, particularly the large altitudinal range (6030–3620 m), almost northerly aspect and steep slope (average ~ 30°). 相似文献
45.
Ahmad Mir Ishfaq J. N. Pattan V. M. Matta V. K. Banakar 《Journal of the Geological Society of India》2013,81(5):647-654
A 4.1 m long sediment core from the Eastern Arabian Sea (EAS) is studied using multiple geochemical proxies to understand the variation of productivity and terrigenous matter supply during the past 100 ka. The temporal variation in element concentration and fluxes of CaCO3, organic carbon (Corg) and Barium excess (Baexc), together, in general indicate a higher productivity during the cold climate and highest during the Last Glacial Maximum (LGM) in particular. This cold climate-increased productivity coupling may be attributed to the shoaling of nutricline due to enhanced convective mixing resulting from the intensified winter monsoon. Increased linear sedimentation rates and fluxes of Al, Fe, Mg, Ti, Cr, Cu, Zn, and V during the cold period also suggest increased input of terrigenous matter supporting intensified winter winds. However, the presence of large abundance of structurally unsupported elemental content (e.g.: Mg-86%, Fe-82% and Al-53%) indicate increased input of terrigenous material which was probably enhanced due to intense winter monsoon. 相似文献
46.
Ground-source geothermal systems are drawing increasing attention and popularity due to their efficiency, sustainability and being implementable worldwide. Consequently, design software and regulatory guidelines have been developed. Interaction with the subsurface significantly affects the thermal performance, sustainability, and impacts of such systems. Reviewing the related guidelines and the design software, room for improvement is evident, especially in regards to interaction with groundwater movement. In order to accurately evaluate the thermal effect of system and hydrogeological properties on a borehole heat exchanger, a fully discretized finite-element model is used. Sensitivity of the loop outlet temperatures and heat exchange rates to hydrogeological, system and meteorological factors (i.e. groundwater flux, thermal conductivity and volumetric heat capacity of solids, porosity, thermal dispersivity, grout thermal conductivity, background and inlet temperatures) are analyzed over 6-month and 25-year operation periods. Furthermore, thermal recovery during 25 years after system decommissioning has been modeled. The thermal plume development, transport and dissipation are also assessed. This study shows the importance of subsurface thermal conductivity, groundwater flow (flux > 10?7 m/s), and background and inlet temperature on system performance and impact. It also shows the importance of groundwater flow (flux > 10?8 m/s) on thermal recovery of the ground over other factors. 相似文献
47.
Quaternary coral reefs of the Red Sea coast, Egypt: diagenetic sequence, isotopes and trace metals contamination 总被引:1,自引:1,他引:0
Abdelbaset S. El-Sorogy Hamdy Nour Emad Essa Mohamed Tawfik 《Arabian Journal of Geosciences》2013,6(12):4981-4991
This study focuses on the diagenetic sequence under marine and meteoric conditions as well as isotopes and trace metals contamination in Quseir and Gebel Zeit areas along the Egyptian Red Sea coast through a series of modern and fossil corals, Porites lutea and Favites pentagona. The diagenetic sequence begins with deposition of thin fringes of syntaxial aragonite and micritic high-magnesian calcite in the modern corals to completely altered Porites and partially altered Favites to low-magnesium calcite in the oldest Pleistocene unit. Average δ18O and δ13C values of Pleistocene corals in the two studied areas were lower than those of modern corals. Values of modern corals and lower fossil unit indicated coralline limestone, while those of middle and upper fossil units indicated fresh water influences. Average values of trace metals in modern corals were higher than those of Pleistocene counterpart except for Mn. Modern coral samples recorded enrichment in the average values of Pb, Zn, and Mn at Quseir area and enrichment in Co, Cu, and Ni at Gebel Zeit area. This may be attributed mostly to different tourist activities, landfill due to increase urbanization and nearby of Quseir area from the old phosphate harbor at El Hamrawin area, as well as oil exploration and production activities in the Gulf of Suez area. Also, results indicated that most samples of Porites have high concentration of trace metals than in Favites, especially in Cu, Zn, Mn, and Pb. This may due to high amounts of intergranular porosity and high total surface area of Porites in contrast to Favites. 相似文献
48.
49.
Sayed A. El-Wakil Essam M. Abulwafa Emad K. El-shewy Abeer A. Mahmoud 《Astrophysics and Space Science》2011,333(1):269-276
The time fractional KdV equation is derived for small but finite amplitude electron-acoustic solitary waves in plasma of cold
electron fluid with two different temperature isothermal ions. The effects of the time fractional parameter on the electrostatic
solitary structures are presented. It is shown that the effect of time fractional parameter can be used to modify the amplitude
of the electrostatic waves (viz. the amplitude, width and electric field) of the electron-acoustic solitary waves. The model
may provide a possible explanation for the low-frequency component of the broadband electrostatic noise in the plasma sheet
boundary layer of the Earth’s magnetotail where the electron beams are not present. 相似文献
50.