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1.
The tritium content of the surface water on the south shore of the Caspian Sea was determined in samples taken in two- to three-month intervals for the period of time from 1960 to 1970. Tritium concentrations following the massive H-bomb testing in 1962 and 1963 were particularly high in this water, much higher than in the surface waters of the open oceans. The data are interesting in connection with the tritium inventories on the continents and with the persistence of inert chemical pollutants in the surface layers of water masses.  相似文献   

2.
The most important source of dissolved manganese, Mn(II), to the Dead Sea is by upward diffusion from bottom sediments. This source contributes about 80 tons of Mn(II) each year. The concentration of dissolved manganese in the Dead Sea is extraordinarily high (7.03 mg 1?1). It appears that the content (some 1.026 × 106 tons) of dissolved manganese in the sea has remained constant during 1977–1979, although oxygen was introduced into deeper layers during the deepening of the pycnocline (1977–1978) and during the overturn of its water masses in the winter of 1978/79. The rate of oxidation of Mn(II) in Dead Sea water is extremely slow hence Mn(II) may practically be considered as the stable form of Mn in Dead Sea waters. Dilution by fresh water causes a pH rise and may facilitate faster oxidation of the dissolved divalent manganese. It is shown here that the shape of the Mn(II) profile, observed in the lake during 1963, may have developed by oxidation of Mn(II) in the more diluted upper layers and subsequent reduction of the oxidation products in the anoxic and more saline deeper layers during 260 years of continuous meromixis.  相似文献   

3.
Depth profiles of the chlorofluoromethanes (CFM), CFCl3 and CF2Cl2, have been obtained together with tritium profiles from water samples collected in the Norwegian Sea between surface and 2800 m depth. CFM analysis was performed by vacuum extraction of the dissolved gases from 500 ml samples of seawater and subsequent gaschromatographic measurement. The CFM concentration decreases with depth to about 10 percent of surface concentration at depths below 2000 m. The same behaviour is found for the tritium content. From a correlation of the CFM and tritium concentration the upper limit of the preindustrial atmospheric CFM levels can be estimated to 5 percent of the present day concentrations.  相似文献   

4.
Summary

In 1958 the U.S. Geological Survey and the U.S. Weather Bureau jointly conducted a study of tritium fallout distribution over the continental United States, Alaska, and Puerto Rico. The observation period extended from early April to late July in most areas. While this was insufficient to cover the decay side of the curve, it was sufficiently long to establish general trends of tritium activity contours. Tritium activities were found to be maximum in the north central part of the country and minimum in coastal areas. The tritium activities show an inverse correlation with chloride concentrations in precipitation. Tritium activities in precipitation appear to be influenced by several “low altitude effects” particularly in storms of brief duration. Ground level tritium activity measurements are not directly representative of tritium in cloud moisture because of these effects.  相似文献   

5.
Future use of tritium in mapping pre-bomb groundwater volumes   总被引：2，自引：0，他引：2  
The tritium input to groundwater, represented as volume-weighted mean tritium concentrations in precipitation, has been close to constant in Tucson and Albuquerque since 1992, and the decrease in tritium concentrations at the tail end of the bomb tritium pulse has ceased. To determine the future usefulness of tritium measurements in southwestern North America, volume-weighted mean tritium levels in seasonal aggregate precipitation samples have been gathered from 26 sites. The averages range from 2 to 9 tritium units (TU). Tritium concentrations increase with site latitude, and possibly with distance from the coast and with site altitude, reflecting local ratios of combination of low-tritium moisture advected from the oceans with high-tritium moisture originating near the tropopause. Tritium used alone as a tool for mapping aquifer volumes containing only pre-bomb recharge to groundwater will become ambiguous when the tritium in precipitation at the end of the bomb tritium pulse decays to levels close to the analytical detection limit. At such a time, tritium in precipitation from the last one to two decades of the bomb pulse will become indistinguishable from pre-bomb recharge. The threshold of ambiguity has already arrived in coastal areas with a mean of 2 TU in precipitation and will follow in the next three decades throughout the study region. Where the mean tritium level is near 5 TU, the threshold will occur between 2025 and 2030, given a detection limit of 0.6 TU. Similar thresholds of ambiguity, with different local timing possible, apply globally.  相似文献   

6.
Mean annual rates of tritium input into the ocean averaged over 5° latitude bands are presented for the major oceans, for the period 1952–1975. The rates are obtained by converting tritium concentrations in marine precipitation into net oceanic tritium input, by means of a hydrological model. The tropospheric tritium pattern is specified on the basis of available observations, and climatological means from the literature are used for the rates of evaporation and precipitation and for the relative humidity in ship's height, that enter the model. Tritium input by water vapor exchange exceeds that by precipitation about three-fold. Tritium input by river runoff and by net tropospheric tritium outflow from the continents is also accounted for. This contribution is small except for the northern Indian Ocean and the North Atlantic.The inputs have hemispheric maxima near 50° latitude. The northern hemisphere inputs were strongly peaked in 1963–1964, whereas temporal changes in the southern hemisphere were much more gradual. By 1972, about 75% of the total oceanic input had been received by the northern ocean. For the Pacific, the computed total input agrees with the actual tritium inventory within the limits of uncertainty (about ±20%). The global tritium inventory is estimated at 1.9 GCi in 1972, which corresponds to an average tritium yield of 0.9 kg tritium per megaton TNT equivalent of nuclear fusion.  相似文献   

7.
In this paper the reaction of the salt‐/freshwater interface due to the changes in the Dead Sea level are elaborated at in details by using the inflows into the Dead Sea, the outflows due to evaporation losses and artificial discharges, and the hydrographic registrations of the Dead Sea level. The analyses show that the interface seaward migration resulted in a groundwater discharge of around 423 Mio m3 per meter drop in the level of the Dead Sea in the period 1994–1998 and of around 525 Mio m3/m in the period 1930–1937. The additional amount of groundwater joining the Dead Sea due to the interface seaward migration was 51 Mio m3 per one square kilometer of shrinkage in the area of the Dead Sea in the period 1930–1937 and 91 Mio m3/km2 in the period 1994–1998. The riparian states of the Dead Sea are nowadays loosing 370 Mio m3/a of freshwater to the Dead Sea through the interface readjustment mechanisms as a result of their over exploitation of waters which formerly fed the Dead Sea.  相似文献   

8.
Tritium concentrations are used to trace water circulation in the Urumqi and Turfan basins in the Xinjiang, western China. Tritium analyses were made for 77 water samples of river waters, groundwaters, spring waters, lake waters and glacier ice collected in summers in 1992 and 1994. The tritium concentrations in the waters are in a wide range from 0 to 125 TU, most of which are considerably high compared with those of most waters in Japan, because tritium levels in precipitation in the area are over ten times as high as those in Japan. River waters originating in glacier regions contain melt glacier, the proportion of which is over 0.5 to river water. The mean resi-dence time of circulating meteoric water in the mountain regions is estimated to be about 15 years. Most groundwaters and spring waters in the flat regions are mainly derived from river waters originating in glacier regions. The groundwater of greatest tritium concentrations in wells in Urumqi City is derived from Urumqi River about 25 years ago. It takes several ten years for river water to pass the underground to many springs. Some groundwaters and spring waters have taken a long time more than 40 years to travel under the ground. Enrichment of tritium in lake water by evaporation is considered to estimate the contribution of groundwater flow to the recharge of lake. Various contributions of groundwater to lakes are inferred for the various type of salinity in closed or semi-closed lakes. The inflow rates of groundwater to salt lakes are small as against fresh water lakes.  相似文献   

9.
As a part of Jordan’s efforts to quantify the effect of the Dead Sea level decline on the precious groundwater resources of the surrounding aquifers, the authors analyzed the historic or predevelopment inflows and outflows of the Dead Sea basin and the resulting water balance which included precipitation, evaporation, surface‐ and groundwaters. The predevelopment situation was taken as the point of departure for the sake of this study. Furthermore, the present situation was analyzed in an attempt to quantify the groundwater inflows into the Dead Sea as a result of drop in the Dead Sea level. The groundwater component and the corresponding saltwater/freshwater interface were taken as the variables to balance the levels of the sea that would have been reached without the contribution of the uncontrolled groundwater inflows as a result of the salt/freshwater interface seaward migration. The present day water balance that includes all the water diversion projects from all riparians indicates serious declines in the Dead Sea level. The effects of the present day level declines on the fresh groundwater/saltwater interface indicate that considerable amounts of groundwater are driven into the Sea as a result of the seaward migration of the freshwater/saline water interface.  相似文献   

10.
Tritium and14C data of the “GOGO I” station at 28.5°N, 121.6°W in November 1971 are reported. The tritium decline between 150 and 350 m depth is as pronounced as was observed on a previous occupation of the same position, station “Geosecs I” in September 1969, and the tritium concentrations below 200 m are unchanged.14C data from the depth range of tritium decline are corrected for fallout14C contribution. The correcting procedure requires simultaneous measurements of14C, ΣCO2, and tritium. It is concluded that the natural absolute14C concentration attains a maximum near 400 m depth, of 7.5% excess over that of surface water.  相似文献   

11.
The high‐density Dead Sea water (1.235 g/cm3) forms a special interface configuration with the fresh groundwater resources of its surrounding aquifers. The fresh groundwater column beneath its surroundings is around one tenth of its length compared to oceanic water. This fact alone indicates the vulnerability of the fresh groundwater resources to the impacts of changes in the Dead Sea level and to saltwater migration. Ghyben‐Herzberg and Glover equations were used to calculate the volumes of water in coastal aquifers which were replaced by freshwater due to the interface seaward migration as a result of the drop in the level of the Dead Sea. For that purpose, the dynamic equation of Glover approach has been integrated to accommodate that type of interface readjustment. The calculated amounts of freshwater which substituted salt Dead Sea water due to the migration of interface are 3.21 · 1011 m3, from a Dead Sea level of –392 m to τ411 m below sea level. The average porosity of coastal aquifers was calculated to range from 2.8 to 2.94%. Geoelectric sounding measurements showed that areas underlying the coastal aquifers formerly occupied by the Dead Sea water are gradually becoming flushed and occupied by freshwater. The latter is becoming salinized due to the residuals of Dead Sea water in the aquifer matrix, the present salinity of which is lower than that of the Dead Sea water. At the same time salt dissolution from the Lisan Marl formation is causing collapses along the shorelines in the form of sinkholes, tens of meters in diameter and depth.  相似文献   

12.
The Dead Sea is a hypersaline terminal lake located in the Rift Valley between Jordan and Israel. In this work a generalised mathematical model describing the behaviour of the Dead Sea has been developed. The model established the condition of the Sea by evaluating a series of ordinary differential equations describing mass balances on the water and major chemical species in the Sea. The Sea was modelled as a two-layer system. The model was validated by comparing its predictions to measured level records. The results obtained highlighted the importance of detailed evaporation modelling, showed the necessity to model the Sea as a two-layer system, validated the usage of average distribution data to estimate the flowrates of rivers, and justified ignoring diffusion effects in further modelling. The model predicted that in the case of continuing current conditions, the level will continue to decline, at a decelerating rate, because the area and evaporation rate are both decreasing. Under these conditions, the model shows that the salinity of both layers will continue to increase, and that seasonal stratification and seasonal crystallisation of gypsum and aragonite will continue.  相似文献   

13.
From 1979 to 1984, the overall water balance of the Dead Sea was characterized by a water deficit. However, an excess of freshwater inflow during the 1979/80 rainy season resulted in a 3-year-long meromictic phase. This was followed by three consecutive overturns of the water column in December 1982, 1983 and 1984. The buildup and dissipation of the seasonal thermocline and halocline is followed throughout this period which covers a wide range of water balance situations. The gravitational stabilities of the summer pycnoclines, measured in terms of N2 3×10−2 s−2, are at least one order of magnitude greater than the values reported in freshwater lakes and oceans. The contributions of temperature and salinity to N2 and to the integrated stability W are examined separately, and their interdependence is pointed out. Two irreversible effects in the evolution of the properties of the water masses are identified: (1) a monotonic increase in the density of the deep waters; and (2) a monotonic shift of the NaCl saturation curve towards higher salinities.  相似文献   

14.
Tritium concentrations were measured in a survey of 24 lakes, 15 wetlands, and 133 groundwaters in the oil sands region of northeastern Alberta and compared with both recent precipitation and precipitation sampled during the 1960s tritium peak caused by atmospheric thermonuclear weapons testing. Water samples from lakes included a group of 14 thaw lakes that had higher runoff attributed to melting of permafrost in peat plateaus within their watersheds. While tritium in all lakes was found to be intermediate between recent and 1960s concentrations, the thaw lakes were found to be significantly enriched in tritium compared with other lakes, as were unfrozen wetlands characterized by a thick sequence of low‐hydraulic conductivity peat. The results provide further evidence of different water sources to the thaw lakes and may indicate that melting of modern permafrost in part formed since the 1950s is occurring in these systems. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

15.
The Dead Sea is a closed lake, the water level of which is lowering at an alarming rate of about 1 m/year. Factors difficult to determine in its water balance are evaporation and groundwater inflow, some of which emanate as submarine groundwater discharge. A vertical buoyant jet generated by the difference in densities between the groundwater and the Dead Sea brine forms at submarine spring outlets. To characterize this flow field and to determine its volumetric discharge, a system was developed to measure the velocity and density of the ascending submarine groundwater across the center of the stream along several horizontal sections and equidistant depths while divers sampled the spring. This was also undertaken on an artificial submarine spring with a known discharge to determine the quality of the measurements and the accuracy of the method. The underwater widening of the flow is linear and independent of the volumetric spring discharge. The temperature of the Dead Sea brine at lower layers primarily determines the temperature of the surface of the upwelling, produced above the jet flow, as the origin of the main mass of water in the submarine jet flow is Dead Sea brine. Based on the measurements, a model is presented to evaluate the distribution of velocity and solute density in the flow field of an emanating buoyant jet. This model allows the calculation of the volumetric submarine discharge, merely requiring either the maximum flow velocity or the minimal density at a given depth.  相似文献   

16.
The Feshcha springs issue in a 4 km long strip on the Dead Sea shores. They constitute two separate groups: a) T-N waters, similar in their salt composition, temperature and radon content to the many other members of the Rift Valley “Tiberias-Noit water association”. The hydrologic, radon, tritium and carbon-14 indicate they are mixtures of recent meteoric waters with ancient (trapped) T-N waters of an age of at least 18000 years. b) Z-Y waters which, like other members of the Dead Sea basin “Zohar-Yesha water group”, originate by a mixing of T-N waters with Dead Sea waters. This is seen in the chemical compositions and is confirmed by the oxygen-18 and deuterium data.  相似文献   

17.
The Dead Sea is the lowest spot on Earth. It is a closed saline lake located in the middle of the Jordan Rift Valley between Lake Tiberias and the Red Sea. Its major tributaries are the Jordan River itself and the Dead Sea side wadis. The Dead Sea has a unique ecosystem and its water has curative, industrial and recreational significance. The level of the Dead Sea has been continuously falling since the early 1930s at an average rate of 0·7 m per year. The water level, as of February 1998, is about 410·9 m below mean sea level. In this paper, a water balance model is developed for the Dead Sea by considering different hydrological components of this water balance, including precipitation, runoff, evaporation and groundwater flow. This model is calibrated based on historical levels of the Dead Sea. Different scenarios are investigated, including the proposed Dead Sea–Red Sea Canal. This project is supposed to halt the shrinking of the Dead Sea and restore it to pre‐1950 levels in the next century. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

18.
Environmental tracers, such as tritium, have generally been used to estimate aquifer recharge under natural conditions. A tritium tracer test is presented for estimating recharge under semi‐arid and irrigated conditions. The test was performed along 429 days (June 2007–August 2008) on an experimental plot located in SE Spain with drip irrigation and annual row crops (rotation of lettuce and melon), in which common agricultural practices were followed in open air. Tritiated water was sprinkled (simulated rainfall) over the plot, soil cores were taken at different depths and a liquid scintillation analyzer was used to measure tritium concentration in soil water samples. Tritium transport, as liquid or vapor phase, was simulated with the one‐dimensional numerical code SOLVEG. Simulations show that the crop water use was below potential levels, despite regular irrigation. Continuous high water content in soil promoted a great impact of rainfall events on the aquifer recharge. The results obtained from tritium tracer test have been compared with other independent recharge assessment, soil water balance method, to evaluate the reliability of the first one. Total recharge from tracer test was 476 mm for the October 2007–September 2008 period versus 561 mm from soil water balance method for the same period, which represents 37.1% and 43.7% of the applied water (1284 mm, irrigation + precipitation), respectively. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

19.
The distributions of dissolved and of particulate iron in the Dead Sea during the period which preceeded its overturn and thereafter (1977–1980) are reported. During 1977–1978, the vertical profiles of the iron phases revealed facets of the mixing pattern: the progressive deepening of the pycnocline, restricted mixing within the upper water mass and penetration of surface waters into the deepest layer. The inventories of particulate iron suggest resuspension of bottom sediments in November 1978 and after the overturn the gradual disappearance from the water column of iron sulfides and iron oxy-hydroxides. Fluxes of iron from and to the lake in the undisturbed meromictic Dead Sea have been estimated: it appears that diffusion of divalent iron from bottom sediments was the major source for the standing crop of iron in the lower water mass. Low settling velocities of solid particles in the dense and viscous Dead Sea is one of the causes for the relatively large concentrations of particulate iron. The rate constant for oxidation of divalent iron in Dead Sea sediment interstitial waters is larger by two orders of magnitude than in other natural waters.  相似文献   

20.
Previous studies have shown that the Red Sea was formed by two stages of sea-floor spreading, with a quiescent period in between. We suggest that these two phases have occurred in different directions. The shape of the central trough indicates that the present-day motion is almost E-W, whereas the total opening, deduced from the shape of the coastlines, is NE-SW. If the axial trough has opened in an E-W direction, the earlier stage of opening was in a direction which made the Dead Sea Rift fall along a small circle to the pole of early opening, and hence suggests that the Dead Sea Rift was a transform fault during this early stage. The later movement gives almost pure extension along the Dead Sea Rift, and this should be seen by normal faulting. Available first-motion studies are not precise enough to confirm or deny this hypothesis.  相似文献   

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