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Shallow groundwater in the northern Negev desert of Israel flows preferentially through a complex system of discontinuities. These discontinuities intersect what would otherwise be a massive, low-conductivity, high-porosity Eocene chalk. Vertical fractures and horizontal bedding planes were observed and mapped along approximately 1,200 m of scanline, 600 m of core and 30 two-dimensional trace planes. A bimodal distribution of size exists for the vertical fractures which occur as both single-layer fractures and multi-layer fractures. A bimodal distribution of log transmissivity was observed from slug tests conducted in packed-off, vertical intervals within the saturated zone. The different flow characteristics between the horizontal bedding planes and vertical-type fractures appear to be the cause of the bimodality. Two distinct conceptual models (discrete fracture network) were developed based on the fracture orientation, size, intensity and transmissivity statistics derived from field data. A correlation between fracture size and hydraulic aperture was established as the basis for calibrating the simulated model transmissivity to the field observations. This method of defining transmissivity statistically based on prior information is shown to be a reasonable and workable alternative to the usual conjecture approach towards defining transmissivity in a fractured-rock environment. 相似文献
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Simultaneous ozone measurements were made at a rural site, 25 km SSW of the city of Jerusalem, and in the center of the city during a period of 28 months. The ozone data were supplemented by SO2, NO/NO
x
,and meteorological measurements at both sites. Elevated ozone concentrations were recorded at the rural site, mostly during the spring months (May and June) during which the monthly averages and the monthly averages of the daily 30 min maximum levels equalled those measured in the city. During the summer months, both average and peak levels were lower at the rural site by 20 and 35 ppb. The increased ozone levels at the rural site were accompanied by a parallel increase of SO2 and NO
x
,suggesting hat the excess ozone at the rural site is a result of a transformation during transport of air pollutants from coastal sources. 相似文献
3.
The fraction of rain that is annually recharged to ground water is a function of the transient quantities of precipitation (wet vs. dry years) as well as other meteorological and geologic factors, and thus it is very difficult to estimate. In this study, we have used long records (20 to 30 years) of precipitation and spring discharge to reconstruct the transient character of yearly recharge. These data sets were used to calibrate numerical ground water flow models on the less than 3 km(2) scale for four separate perched karstic aquifers in the Judean and Samarian Mountains of Israel. The stratification and karstic character of the local carbonate rock aquifers cause ground water to flow through discrete dissolution channels and to discharge at isolated springs. An innovative, dual-porosity approach was used where a finite-difference solution simulates flow in the rock matrix, while the karstic channels are simulated using computationally simple drains. Perched conditions are also simulated innovatively using MODFLOW by treating the bottom unsaturated layer as if it is saturated, but by assuming zero pressure head throughout the "unsaturated" layer. Best fitting between measured and computed spring hydrograph data has allowed us to develop a set of empirical functions relating measured precipitation to recharge to the aquifer. The generic methodology presented gives insight into the suspected changes in aquifer recharge rates between particularly wet or dry years. 相似文献
4.
The photochemical oxidation of SO2 in the presence of NO and C3H6 was studied in a 18.2 liter pyrex reactor. When light intensity, irradiation time and SO2 concentration were constant, SO4
2- concentration, derived from the total volume of aerosol produced, peaked when [C3H6]/[NO] was approximately 6.0. Another increase im SO4
2- formation was reached at very high ratios (>50). The experimental observations are consistent with the two SO2 oxidation mechanisms. At low [C3H6]/[NO] ratios, the processes proceed via the HO–SO2 reaction, while at high ratios the O3–C3H6 adduct is assumed to oxidize SO2 to produce SO4
2- aerosols. 相似文献
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Fish Biodiversity in the Vermetid Reef Of Shiqmona (Israel) 总被引：1，自引：0，他引：1
Abstract. A study of the structure of the fish community associated with a vermetid reef at Shiqmona, Israel, revealed the highest fish biodiversity (36 species) of any habitat along the Mediterranean coast of Israel. Despite the prevalence of fish of Erythrean origin in the Levantine littoral, the benthic fish community at the site is entirely autochthonous. The families richest in members were the Blenniidae and the Gobiidae. Eighteen species are benthic, sixteen supra-benthic and two pelagic. 相似文献
6.
Ambient particulate sulfate measurements have been intermittently performed at a rural site in Israel over a period of more than two years. Concurrent measurements of ambient pollutants (SO2, NO–NOx, and O3), as well as meteorological data, were also carried out. The daily data included four particulate sulfate samples representing four successive 6 h accumulating periods. The measured concentrations of sulfate ions ranged from a low 2 g m-3 observed during the winter season to a high of >50 g m-3 obtained during the summer. Little correlation was obtained between the sulfate concentration and either O3 or SO2, although sulfate and O3 showed a similar diurnal and annual trend. Based on the data distribution and on a photochemical model, it was concluded that a large part of the particulate sulfate observed at the eastern coast of the Mediterranean Sea must be related to long-range transport from distant sources. 相似文献
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