Dissolved oxygen in the Dead Sea— seasonal changes during the holomictic stage

Measurements of dissolved oxygen, density and temperature were con ducted in the Dead Sea between August 1987 and December 1989. Oxygen concentrations were found to vary around an average value of 0.8 mlSTP (standard temperature and pressure) per kg. Dissolved oxygen variations were found to reflect both physical processes (a deepening of the epilimnion, a turnover etc.) and chemical processes (oxidation reduction). Transport coefficients for the oxygen exchange across the air/sea interface were found to be generally low compared to expected values based on laboratory experiments; the presence of surface films which inhibit the gas exchange rates under calm weather conditions is suspected. During stormy weather, the exchange rates were considerably higher, suggesting that the entrainment of bubbles was involved in the gas exchange process. Contribution No. 95, Department of Environmental Sciences and Energy Research. The Weizmann Institute of Science     

Bacterial activities in the Dead Sea, 1980-1991: survival at the upper limit of salinity

Since the mass development of halophilic bacteria in 1980 and the subsequent decline of the community in 1982, no new mass development of bacteria has occurred in the Dead Sea, and bacterial numbers have remained extremely low. The lake’s salinity, and more specifically the divalent cation concentration, have increased greatly during the last ten years. To quantitate the activity of the community of heterotrophic bacteria in the Dead Sea water column, rates of incorporation of amino acids, glycerol, and acetate were measured, both during the 1980–1981 bloom and in recent years. With the development of the bloom, rates of incorporation amino acids, glycerol and acetate increased. Concomitant with the decline in bacterial numbers, the incorporation rates of amino acids and acetate decreased at the end of 1980-beginning of 1981, while glycerol incorporation rates remained high for one more year. Measurements in 1989 and in 1991 showed very low but significant incorporation rates (three to four orders of magnitude lower than during the 1980–1981 bloom). By the use of specific inhibitors, it was shown that the remaining activity was due to halophilic archaeobacteria. The mechanism of the long-term survival of a small active bacterial community in the Dead Sea in the absence of primary producers and other obvious sources of organic carbon, and at divalent cation concentrations greatly exceeding those enabling growth, is still unknown.     

Slip rate on the Dead Sea transform fault in northern Araba valley (Jordan)

The Araba valley lies between the southern tip of the Dead Sea and the Gulf of Aqaba. This depression, blanketed with alluvial and lacustrine deposits, is cut along its entire length by the Dead Sea fault. In many places the fault is well defined by scarps, and evidence for left-lateral strike-slip faulting is abundant. The slip rate on the fault can be constrained from dated geomorphic features displaced by the fault. A large fan at the mouth of Wadi Dahal has been displaced by about 500 m since the bulk of the fanglomerates were deposited 77–140 kyr ago, as dated from cosmogenic isotope analysis (¹⁰Be in chert) of pebbles collected on the fan surface and from the age of transgressive lacustrine sediments capping the fan. Holocene alluvial surfaces are also clearly offset. By correlation with similar surfaces along the Dead Sea lake margin, we propose a chronology for their emplacement. Taken together, our observations suggest an average slip rate over the Late Pleistocene of between 2 and 6 mm yr⁻¹, with a preferred value of 4 mm yr⁻¹. This slip rate is shown to be consistent with other constraints on the kinematics of the Arabian plate, assuming a rotation rate of about 0.396° Myr⁻¹ around a pole at 31.1°N, 26.7°E relative to Africa.     

死海溴镁资源开发利用现状

对以色列和约旦死海中溴镁资源的开发综合利用进行了解述。包括死海卤水组成,资源储量,溴及其衍生物的镁化学制品生产现状。