Showing papers on "Water environment published in 1976"

Mercury uptake by fish and biomethylation mechanisms

Abstract: the 1950's and the ornithological di saster in Sweden in the 1960's, the health hazard imposed by environmental mercury pollution has received international atten tion. It seems that the form of mercury discharged into the environment is unim portant, because any form of mercury may be converted to methylmercury by micro organisms. Numerous studies have been directed toward delineating the sources of mercury contamination, its movement in the environment, and the route through which mercury reaches human beings. The general physical-chemical properties of mercury have been studied since the days of alchemy; however, a paucity of data exists concerning mercury's dynamic properties. These include the mechanisms by which mercury is released, mobilized, and subsequently transformed into methyl mercury in the water environment and the external environmental factors affecting these transformations. Several studies have been conducted in volving the biomethylation occurring in sediments and the subsequent fish uptake of the methylmercury produced. Unfortu nately, the majority of these studies were conducted without proper consideration of environmental factors such as temperature, degree of organic pollution, chloride ion concentration, mercury concentration, and pH. Furthermore, no known experiments have varied these factors in a single study. It is obvious that the methylation of mer cury contained in sediments needs quantifi cation in terms of different environmental conditions, and those factors affecting methylmercury uptake by fish require eluci dation. Objectives The objectives of these studies were (a) to examine the dynamic properties of in organic mercury and methylmercury, (b) to determine the uptake rates of methyl mercury biosynthesized in sediment by fish and the effects on the uptake rates of varying environmental conditions, and (c) to observe the effects of varying environ mental parameters on the overall methyla tion activities of microorganisms. In addi tion, an estimate of the retention time of mercury in contaminated sediments was to be ascertained. Methodology

Mineral Metabolism During the Ontogenesis of Rainbow Trout (Salmo gairdneri)

Abstract: Rainbow trout (Salmo gairdneri) eggs were collected from three females, fertilized by the milt of two males per female, and incubated separately. Samples were taken before fertilization, at +0.5 h and on days 1, 1.5, 3, 4, 5, 13, 17, 21, at hatching (23 days), and on day 37, immediately after postyolk absorption. The water environment contributed an estimated minimum 26% of the Na, 30% of the Fe, and 13% of the Zn found at hatching. Derivation of Ca, Na, K, Fe, and Zn from the water environment at postyolk absorption was estimated to be at least 70, 76, 45, 68, and 2%, respectively. All the P and Cu at hatching and in the larva could have been derived from the unfertilized oocyte.

Purging a Muddy–Earthy Flavor Taint from Rainbow Trout (Salmo gairdneri) by Transferring to Artificial and Natural Holding Environments

Abstract: Studies were conducted to determine the length of time required to purge a muddy–earthy flavor taint from pond cultured rainbow trout (Salmo gairdneri) transferred to two different clear water environments. Sensory data from trained judges show that this required 5 days for fish transferred to a rapidly changing purified artificial water environment and 16 days for fish transferred to a relatively static natural water environment to reduce this taint to or below threshold levels of recognition.

Environmental Effects on Graphite-Epoxy Fatigue Properties

Abstract: Effects of torsional and flexural fatigue on the long-time Integrity of advanced graphite-epoxy structural composites have been investigated. Torsional fatigue tests were run at stress ratios of R = 0 (zero to maximum, repeated) and R = -1 (zero mean stress) on unidirectional, angleply, and woven graphite fiber materials in air and water at room temperature and at 74 C. Flexural fatigue tests (four-point bending) with R = -1 were run in air and water at room temperature, and with R = 0 in air. Results show that, in torsional cycling, both water environment and higher test temperature contribute to significant degradation of torsional stiffness. The degradation of stiffness from torsional stress cycling was observed to be much greater with R = -1 than with simple R = 0 cycling. The effect of environment also is greater in the fully reversed cycling. Flexural fatigue results on +/- 30 deg material show a large fatigue effect, with fatigue limits of less than 50% and 30% of the static failure strength for specimens tested under stress ratios of R = 0 and R = -1, respectively. Compliance measurements indicate that the final failures are preceded by damage initiation and accumulation, which begins at about 1% of the specimen life.

Temperature and rate dependent fracture in glass-filled polystyrene

Abstract: The rate and temperature dependent fracture behavior of glass-filled polystyrene has been investigated over the crack speed range of 1013 to 1 mm/sec and in the temperature range 283 to 396°K for three environmental conditions: (i) air; (ii) water; and (iii) hot water exposure at 363°K and subsequent drying. Relationships between fracture toughness (Kc), crack speed and temperature have been obtained experimentally and analysed according to the concepts of fracture mechanics and reaction rate theories. Crack propagation in air is shown to be controlled by a β-relaxation process associated with crazing. Activation energies of 200 ∼ 210 kj/mole in air and 80 ∼ 120 kj/mole in water are reported. At a given temperature and crack speed, the glass-filled polystyrene is shown to display smaller crack propagation resistances in a water environment when compared with the air results. Specimens subjected to hot water exposure and then tested after drying also possess less cracking resistance. This toughness degradation phenomenon is a result of the damaging effects of the water which penetrates into the glass-filled composite.

Tests of Oil Recovery Devices In a Broken Ice Field

Abstract: As part of its Arctic pollution response program, the United States Coast Guard recently completed a two phase testing program of oil spill recovery devices operating in a broken ice field at below freezing temperatures. The Phase I program consisted of tests of Lockheed and Marco oil spill recovery devices to determine their performance when operating in an oil/ice/water environment. Tests were conducted in both salt and fresh water ice, with No.2 fuel oil and a crude oil similar to Prudhoe Bay crude oil, and in nominal oil thickness of 1/2 inch and 2 inches. These tests demonstrated that with minor hardware modifications and the proper operating procedures both devices can successfully recover oil spilled in a broken ice field of moderate ice piece size. The Phase II test program, was primarily directed towards the evaluation of modifications intended to improve the performance of the devices when operating in broken ice cover, and the determination of the variation in oil recovery performance with variation in forward speed and drum or belt rotational speed. Among additional secondary tests incorporated in the Phase II program were spreading tests to determine the natural equilibrium slick thickness of the oils tested, and brief oil recovery performance tests of the oil recovery devices at low temperatures in open water. Tests of the modified Lockheed and Marco devices demonstrated that the modifications did improve their performance when operating in broken ice cover. The spreading tests demonstrated that light oils will spread to a very thin layer, whether in open water or in broken ice cover. Heavy oils in broken ice cover will, however, achieve a natural equilibrium thickness many times greater than the open water thickness due to the partial containment of the oil by the broken ice pieces.

Tectonic Framework of Sedimentation in the Western Part of the Palnad Basin, Andhra Pradesh

Abstract: The lithologic character of sediments, geometry and sedimentary characters of the formations belonging to the Palnad Basin have been taken into consideration in interpreting the probable tectonic framework of sedimentation and tectono-environmental classification of sedimentary formations in the western part of the Palnad basin. The Banganpalli quartzites were deposited in the littoral to infra-littoral environment under stable shelf conditions. The Narji limestones were deposited in infra-littoral to neritic environment under stable shelf conditions. Due to uplift the environment changed to infra-littoral and quiet water environment, when the Auk shales were deposited. The Paniam quartzites were deposited in the littoral to infra-littoral environment under stable shelf conditions with minor tectonic instability in certain local areas where positive elements were active during the uplift of the basin. The Kundair limestones and shales were deposited in neritic zones under reducing environment on stable shelf.

Diving gas recovery apparatus

Abstract: An improved diving habitat for providing breathing gas to a diver in which expired breathing gas is recovered from the habitat utilizing an indirect fluid coupling which is in fluid communication with the interior of the habitat and with a recovery line adapted for connection to a diving gas reconditioning system, the coupling providing for the transfer of the expired breathing gas from the habitat to the recovery line under normal conditions and further providing for a flow of water to the recovery line from the water environment in the event of a dangerous change in pressure in the recovery line.