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101.
Fred M. Phillips Stanley N. Davis Peter Kubik 《Ground Water Monitoring & Remediation》1990,10(3):106-113
Chlorine-36 has been produced in large amounts by hundreds of nuclear explosions on the Nevada Test Site as well as 12 off-site explosions at eight locations in five states. Continued monitoring of the redistribution of radionuclides by subsurface water is of concern in most of the areas affected by the detonations. Chlorine-36 has the following advantages as a built-in tracer for this redistribution: its mobility is equal to or greater than water, its long half-life assures its continued usefulness over long periods, collection and storage of samples is simple, it is not subject to vapor transport at ordinary temperatures, its natural background is very low, and it does not form insoluble precipitates. Chlorine-36 from the Gnome event near Carlsbad, New Mexico, illustrates how 36 C1 can be used to help study the redistribution of radionuclides in the soil profile. Chlorine-36 is also potentially useful as a tracer to study movement of contaminants around large nuclear reactor complexes and near respositories for radioactive waste. 相似文献
102.
Clifford R. Stanley 《Mathematical Geosciences》1990,22(8):933-956
Recent publications have demonstrated that the composition of a system can be described by the angles which define the vector resulting from the projection of the composition onto the unit hypersphere. Although published trigonometric relationships allow determination of the angles in any number of dimensions, no general hyperdimensional recursive formulae exist for the calculation of these quantities and their variances and covariances. A general methodology for calculating the angles which describe the compositions of systems in any number of dimensions is presented. These angles can be used to calculate statistics (central moments and resultant vectors) describing the central tendency and dispersion among rock compositions, as well as to quantify the angular differences between compositions. Equations that relate the variances and covariances of these angular variables to the variances and covariances of the actual component proportion variables are presented, allowing projection of these measurements from one reference frame to another (cartesian to spherical and vice versa). 相似文献
103.
104.
Fish assemblages that included known predators of benthic crustaceans were compared between kelp and barren habitats in northeastern New Zealand using baited underwater video census methods. The benthic-feeding fish were observed in winter, spring/summer and autumn, as well as during night-time in spring/summer. Overall, the fish assemblages varied between barren and kelp habitat, being most marked in winter. Individual benthic-feeding species, such as grey mao mao (Scorpis lineolatus) and leatherjacket (Meuschenia scaber) were associated with barren habitat, while the spotted wrasse (Notolabrus celidotus) was more strongly associated with kelp habitat. The results suggest that changes in habitats on coastal reefs affect populations of species that are benthic predators, which may in turn influence the distribution and abundance of their prey species, such as juvenile spiny lobsters. 相似文献
105.
Palygorskite is a clay mineral widely distributed in late Quaternary deposits of the eastern Mediterranean, where, locally,
it proves an ideal tracer of sediment dispersal. This study shows that the origin of this mineral is not limited to African
sources. Cores containing late Pleistocene to recent sediment record the transport of palygorskite from the Plain of Helos
on the Peloponnesus to specific deep basins along the Hellenic Arc. Palygorskite, commonly concentrated in the silt size fraction,
may be overlooked in studies that focus only on the <2 μm fraction. In this region we find that the detrial palygorskite distribution
is partially controlled by size-sorting effects related to gravity-induced transport processes. In consequence, comprehensive
compositional analyses should be made both on the silt and clay fractions. 相似文献
106.
We investigated the toxicities of six drilling muds, toxicities of mud fractions (supernatants and suspensions) and the toxicities of common mud components—barite and bentonite (particulates) and ferrochrome lignosulfonate (soluble)—to the stage I larvae of six species of shrimp and crab. The drilling muds we tested were not very toxic to these larvae: LC50's for supernatants ranged from 0·6 to 82% (vol/vol). Shrimp larvae were slightly more sensitive than crab larvae.Drilling muds were not rapidly toxic, in contrast to toxicants such as the water-soluble fractions of oil. Supernatants, prepared by centrifuging whole muds, were mildly toxic. Suspensions were more toxic than supernatants and toxicity was greatest when particulates remained suspended: for example, used Cook Inlet mud suspensions were about seven times more toxic than supernatants. The toxicity of used Cook Inlet mud was therefore primarily due to suspended solids (88%) rather than chemical toxicity: ferrochrome lignosulfonate was relatively toxic alone, but accounted for only about 6% of the toxicity of used Cook Inlet mud suspensions. Contributions of particulates to mud toxicities varied considerably. Barite and bentonite were not very toxic when tested alone. The toxicity of one mud was caused by its high alkalinity. 相似文献
107.
Sand-sized terrigenous material from 450 samples representing 24 piston cores is used to compare slope, perched slope basin, and trench apron, plain and margin depositional environments within the Hellenic Trench west of the Peloponnesus. Recognition of three stratigraphically defined layers in the core sections served as a basis for evaluating changes in time. Statistical testing showed that within the upper defined layer (0–5700 yrs. B.P.) terrigenous grains are distributed rather uniformly throughout the slope and basin complexes in contrast to distributions in underlying layers (5700–17,000 and 17,000–45,000 yrs. B.P., respectively. These distributions reflect intense reworking by gravitative processes as evidenced by sediment structures, incomplete slope sections, high accumulation rates, and dilution of sapropels. The homogeneity of the upper layer is explained by failure and downslope transport of sediments that were deposited on the slope during lower stands of sea level. The quantitative analyses performed highlight the rapidity by which land-derived sediments by-pass high-relief slopes, temporarily reside in perched basins on the slope, and ultimately are dispersed to distal trench apron and basin environments by sporadic gravity flows. 相似文献
108.
Cellulose levels in the sediments of Loch Linnhe and Loch Eil were measured over a period of years following the introduction of pulp mill effluent to system. Cellulose levels in experimental sediment systems subjected to pulp fibre inputs at levels simulating various possible loch input levels were measured and compared. No permanent build up of cellulose in either the loch systems or the experimental systems was observed, even at high input levels.Pulp fibre degradation rates were measured experimentally using two different techniques. No difference was found between the degradation rates of wet and predried fibre.Degradation rates equivalent to 0·2 g dry fibre m?2 day?1 were found in areas of low fibre input and 0·5 g dry fibre m?2 day?1 in areas of high input were recorded. These rates were of the same order as, but somewhat lower than, the probable input rates to the sediments in Loch Eil. Speculations as to possible reasons for this are advanced. 相似文献
109.
Stanley D. Brunn 《The Professional geographer》2018,70(2):209-218
The American Association of Geographers (AAG) president's annual address is considered an important statement about how she or he views the state of the discipline or one's research specialties. Building on previous studies on journal and individual impacts, this study measures the impacts of addresses using Google Scholar data and the Web of Science score. Using these data I classify the addresses into three distinct categories: alpha, beta, and gamma. The results reveal wide and substantial differences in Scholar ratings and Web of Science scores. A few have very high ratings, but many more are in the gamma category. Addresses by women and men presidents that promote new fields of study, extend geographic research to interdisciplinary audiences, and encourage the topics and frameworks of existing fields have higher ratings than those that appeal to more specialized audiences. 相似文献
110.
Abstract A new ENSO SST index is documented that is strongly correlated to the core ENSO phenomenon. The SST anomaly in much of the east‐central and eastern tropical Pacific is closely related to ENSO. However, the anomaly from approximately the centre of the eastern half of the equatorial Pacific westward to near the date line is suggested to be most strongly ENSO‐related when data spanning the most recent several decades are used. This is the case both with respect to (1) strength of association with other oceanic/atmospheric ENSO‐related anomalies (both simultaneously and as a time‐delayed predictand), and (2) impact on remote worldwide climate anomalies. This observational insight was lacking in the early 1980s when the four “Niño” regions were developed. While a firmer dynamical foundation for this regional preference still needs to be established, the region straddling Niño 3 and Niño 4 may be regarded as an appropriate general SST index of the ENSO state by researchers, diagnosticians and forecasters. A dataset of this index, called “Niño 3.4” (5°N‐5°S, 120–170°W), is maintained on the Internet, shown in the Climate Diagnostics Bulletin, and provided in the Appendix of this note. 相似文献