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71.
The effects of thermal discharges from the Oyster Creek Nuclear Generating Station at Barnegat Bay, New Jersey, are recorded
in the microstructural growth ofMercenaria mercenaria, a common coastal marine pelecypod. The analysis of the shell microstructure shows that this bivalve acts as an effective
monitor of the environmental conditions existing in the marine waters adjacent to the power station. Many physiological and
environmental events such as spawning, winter (freeze) shocks, summer (heat) shocks, thermal shocks, tidal cycles, and major
storms are clearly recorded in the shell microstructure. The exact time of occurrence of these events can be determined by
counting daily growth increments backwards from the outer shell margins of freshly killed individuals.
Microstructural growth patterns reflected in Barnegat Bay specimens indicate that these pelecypods were affected mainly by
temperature extremes, temperature variations, tides, type of substratum, and age. Growth patterns in specimens from areas
surrounding Oyster Creek (affected by thermal effluent) are significantly different from those from other bay localities (unaffected
by thermal effluent).Mercenaria mercenaria within approximately a 1.6km radius of Oyster Creek show a lower summer growth rate (10 percent to 25 percent lower) and
a greater number of growth breaks (2 to 6 more per clam) than those away from the creek. The lower summer growth rates occur
in bivalves subjected to the effluent because the added heat during the summer months causes water temperatures to exceed
a critical threshold for optimum growth in the species. The greater number of growth breaks takes place, in turn, because
many of the breaks (thermal shock breaks) are generated by rapidly fluctuating temperatures associated with abrupt shutdowns,
massive load reductions and rapid renewal of operations following shutdowns or load reduction periods at the nuclear power
station.
In addition, the effluent may be upsetting natural spawning events in the clams when abrupt changes in power station operations
overlap with spawning periods. In this respect, spawning may be precluded by sharp temperature changes which result in physiological
shocks to the animal. 相似文献
72.
Ernest W. Peterson Peter A. Taylor Jørgen Højstrup Niels Otto Jensen Leif Kristensen Erik L. Petersen 《Boundary-Layer Meteorology》1980,19(3):303-313
Observations of flow over complex terrain taken at Risø during June–July 1978 and numerical studies confirm earlier findings that small variations in surface elevation have significant effects on mean wind profiles. Measured shear stresses in the nonequilibrium region of the flow are consistent with theory but quite different from those obtained assuming simple flux-profile relationships. These findings imply that flux-profile relationships can be quite complicated over other than simple homogeneous terrain. 相似文献
73.
A Three-Dimensional Global Model Study of Carbonyl Sulfide in the Troposphere and the Lower Stratosphere 总被引:4,自引:0,他引:4
Erik Kjellström 《Journal of Atmospheric Chemistry》1998,29(2):151-177
Global distributions of carbonyl sulfide and carbon disulfide have been calculated with a three-dimensional global model of the atmospheric general circulation (ECHAM). The model calculates a global sink strength for carbonyl sulfide of 0.3 Tg S yr-1, with vegetation uptake being the largest sink. With this sink strength, the sources have to be close to the lower limit of the present estimate in the literature. The calculated mixing ratios are higher in the Southern Hemisphere than in the Northern Hemisphere. This interhemispheric gradient is the opposite of what is observed demonstrating that the present knowledge of the distribution of sinks and sources is not fully adequate. The model calculations support the idea that the open oceans could act as a net sink of carbonyl sulfide. The calculated stratospheric photolysis of carbonyl sulfide constitutes about 4% of the total sink of carbonyl sulfide. A stratospheric production of sulfate from carbonyl sulfide of 0.013 Tg S yr-1 is obtained, which is 3 to 12 times less than what is needed to maintain the stratospheric sulfate aerosol layer. Although these results are associated with uncertainties, due to the low upper boundary and coarse vertical resolution of the model, they support recent findings of a low stratospheric production of sulfate from carbonyl sulfide. Instead, sulfur dioxide transported from the troposphere is calculated to be the most important precursor for the stratospheric sulfate aerosol layer. 相似文献
74.
Erik Thorson Brown Robert F. Stallard Matthew C. Larsen Didier L. Bourls Grant M. Raisbeck Franoise Yiou 《Earth and Planetary Science Letters》1998,160(3-4):723-728
Accurate estimates of watershed denudation absent anthropogenic effects are required to develop strategies for mitigating accelerated physical erosion resulting from human activities, to model global geochemical cycles, and to examine interactions among climate, weathering, and uplift. We present a simple approach to estimate predevelopment denudation rates using in-situ-produced cosmogenic 10Be in fluvial sediments. Denudation processes in an agricultural watershed (Cayaguás River Basin, Puerto Rico) and a matched undisturbed watershed (Icacos River Basin) were compared using 10Be concentrations in quartz for various size fractions of bed material. The coarse fractions in both watersheds bear the imprint of long subsurface residence times. Fine material from old shallow soils contributes little, however, to the present-day sediment output of the Cayaguás. This confirms the recent and presumably anthropogenic origin of the modern high denudation rate in the Cayaguás Basin and suggests that pre-agricultural erosional conditions were comparable to those of the present-day Icacos. 相似文献
75.
76.
77.
Erik Kiviat 《Estuaries and Coasts》1978,1(3):196-200
The literature is reviewed and analysis made of references to more than 60 vertebrates that use lodges or bank burrows built by the muskrat,Ondatra zibethicus L. Muskrat homes are important to turtles, waterfowl, terns, carnivores, rodents, and other species for shelter, nesting, getting above the water, or seeking food. No use is obligate but the availability of muskrat homes may limit some species. Effects on vertebrate associates should be considered when muskrat populations are manipulated. 相似文献
78.
79.
William A. Olsson 《Tectonophysics》1974,24(3):277-285
Two fundamentally distinct types of microfractures are present in an experimentally deformed limestone: subaxial microfractures and microfaults. Macroscopic faults are composed of coalesced microfaults and are not related to the subaxial microfractures. A high-temperature mechanical instability occurs at temperatures of 200° C and above when the confining pressure is 600 bars or less. 相似文献
80.
Erik M. Horstman Kathelijne M. Wijnberg Alfons J. Smale Suzanne J.M.H. Hulscher 《Ocean & Coastal Management》2009,52(12):593-611
The potential impacts of climate change on coastal zones combined with the ever increasing number of people living in these areas, motivate a more long-term perspective in coastal management. To explore whether such a perspective raises the need for developing coastal management strategies at larger spatial scales, this paper presents a case study for the dune-protected Holland coast. Long-term (200 years) coastal management strategies are set-up at different levels of spatial aggregation, accounting for specific characteristics of the coast itself and for types of land use in the hinterland. Using a combination of multi-criteria analysis and cost-benefit analysis the new coastal management strategies are compared to the long-term continuation of present coastal management practice. It appears that the large uncertainties that inevitably accompany a long-term perspective do not preclude the comparison of long-term coastal management strategies. Additionally, it appears that a long-term perspective favors solutions for coastal defense enhancement that are more spatially extended and alongshore uniform than those emerging from continuing today's coastal management practice for two centuries. 相似文献