Salinity stress in harpacticoid copepods     

Colin M. Finney 《Estuaries and Coasts》1979,2(2):132-135

Three species of intertidal harpacticoid copepods,Tigriopus japonicus, Tachidius brevicornis andTisbe sp., were tested for their response to salinities ranging from 0‰ to 210‰. At 90‰Tigriopus became dormant, but could be reanimated if placed in 30‰ seawater within 18 hours.Tachidius became dormant at 60‰ but could also be revived if placed in 30‰ seawater.Tisbe died shortly after an exposure to seawater of 45‰. Death was brought about inTigriopus andTachidius by salinities of 150‰. Naupliar, copepodite, and adult stages ofTigriopus withstood the salinities equally well, while egg sacs could tolerate five times the length of exposure of these stages. The respiratory rate ofTigriopus was 3.76 (±1.32) μl 0₂ hr^?1 for active adults and 0.03 (±0.01) nl 0₂ hr^?1 mg dry wt^?1 for adults in the dormant state. The duration of dormancy, with successful revival, appears to be limited to the time before the loss of the vital water content of the tissues due to the high osmotic pressure. The ability to enter dormancy in times of stress may have high survival value to some intertidal copepods.  相似文献   

Bedrock freeze-thaw weathering regime in an alpine environment,colorado front range     

Colin E. Thorn 《地球表面变化过程与地形》1979,4(3):211-228

Reduced major axis analysis is used to describe monthly temperature averages for daily maxima, minima, means and ranges at a sequence of bedrock microenvironments in the alpine zone of the Colorado Front Range. Seven thermistors buried at 1 cm in bedrock provide comparative data on easterly, southerly and westerly aspects, and also upon the impact of snow accumulation (?0.5m to ≥4.0m deep) against an east-facing rock wall. Intersite temperatures commonly differ by less than 5°C and, rarely, by more than 10°C. The freezing intensity of freeze-thaw cycles occurring within the confines of a seasonal snow patch rarely dropped to ?5°C, while at snowfree, vertical faces freezing dropped to ?5°C quite commonly. Comparison with laboratory established criteria for effective freeze-thaw weathering (abundant moisture and freezing to at least ?5°C) suggests that moisture rich microsites lack adequate freezing intensity, while adequately frozen sites lack moisture. Available data suggest that the overlap between freeze-thaw and hydration weathering requires careful re-evaluation.  相似文献   

Experimental hydrogen isotope studies,II. Fractionations in the systems epidote-NaCl-H₂O,epidote-CaCl₂-H₂O and epidote-seawater,and the hydrogen isotope composition of natural epidotes     

Colin M. Graham  Simon M.F. Sheppard 《Earth and Planetary Science Letters》1980,49(2):237-251

The hydrogen isotope fractionation factors between epidote and aqueous 1 M and 4 M NaCl, 1 M CaCl₂ solutions, and between epidote and seawater, have been measured over the temperature range 250–550°C over which the degree of dissociation of dissolved species varies significantly. Measured fractionations at 350°C are decreased by up to 12‰, 9‰ and 7‰ relative to pure water in seawater, 1 M CaCl₂ and 1 M NaCl respectively, while above 500°C fractionations are not measurably dependent on fluid composition. Water—solution fractionation factors are derived which are generally applicable to the correction of mineral—water hydrogen isotope fractionations for the composition of the fluid phase.The hydrogen isotope compositions of natural epidotes are interpreted in the light of experimental fractionation data for situations where temperature, δD (fluid), and, in some cases, fluid chemistry, are independently known. Epidotes from active geothermal systems have hydrogen isotope quench temperatures consistent with or close to measured well temperatures unless the measured temperature has declined substantially since epidote formation or there is uncertainty in the D/H ratio of the water associated with the epidote because of isotopic heterogeneity in the well waters. Hydrothermal and metamorphic epidotes show closure temperatures of 175–225°C and 200–250°C. There is no evidence that retrograde metamorphic fluids, if present, are isotopically different from prograde fluids.The water-solution fractionations indicate strong solute-solvent interactions between 250 and 450°C and imply that both dissociated and associated species contribute to the fractionation effects through modification of the orientations and structure of the water molecules. Solute-solvent interactions become negligible at temperatures around 550°C.  相似文献   

Sedimentary noble gases     

F.A. Podosek  M. Honda  M. Ozima 《Geochimica et cosmochimica acta》1980,44(11):1875-1884

This paper presents experimental data for the trapped noble gas contents in a variety of shales and related samples. These data, along with those previously available, indicate that the normal sedimentary rock pattern is one of progressive enrichment of the heavier gases in comparison with the proportions in air, from which sedimentary rock gases were presumably acquired. Within this normal pattern, however, variations considerably beyond an order of magnitude characterize both abundance and composition, so that multiple processes appear to be necessary to account for trapping of noble gases in sedimentary rocks. Relative to the normal pattern a number of cases of anomalous Ne enhancement occur. This unexplained phenomenon, previously thought to be exotic, must now be considered unexceptional.Noble gases in air occur in approximately the ‘planetary’ proportions characteristic of meteorites, except for more than an order of magnitude deficiency of Xe. It is commonly held that atmospheric noble gases are indeed planetary, the Xe deficiency in air being made up by the inventory in sedimentary rocks. We consider that while this hypothesis cannot be proved false the available data do not support it. At least equal weight should be given to the alternatives: either that (preferentially) Xe has failed ever to become part of the atmosphere or that the total terrestrial noble gas inventory is simply not planetary.  相似文献   

Pumping Test Analysis for a Tidally Forced Aquifer   总被引：3，自引：0，他引：3  

Michael G. Trefry  Colin D. Johnston 《Ground water》1998,36(3):427-433

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Half-life of 92Nb     

Tomoko Makino  Masatake Honda 《Geochimica et cosmochimica acta》1977,41(10):1521-1523

The long-lived nuclide ⁹²Nb together with ⁹¹Nb and ⁹⁴Nb were produced from Mo by neutron irradiation. The activities of the nuclides were determined by γ spectroscopy and the atomic abundances were determined by mass spectrometry. Intercomparison of ⁹²Nb and ⁹⁴Nb activities and abundances yielded a value for half-life $\text{(}{}^{92}\text{Nb) = (3.3 ± 0.5) × 10}{}^7$ yr based on a value for half-life $\text{(}{}^{94}\text{Nb) = 2.0 × 10}{}^4$ yr. The same value was obtained within errors from absolute counting data and dilution analysis.  相似文献   

Reviews     

A. T. Miesch  A. C. Cook  John W. Harbaugh  H. Colin  P. H. A. Sneath  Douglas M. Hawkins  Martin A. Buzas  D. F. Merriam 《Mathematical Geosciences》1974,6(2):207-217

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Modelling the chloride signal at Plynlimon,Wales, using a modified dynamic TOPMODEL incorporating conservative chemical mixing (with uncertainty)     

T. Page  K. J. Beven  Jim Freer  Colin Neal 《水文研究》2007,21(3):292-307

The application of a modified version of dynamic TOPMODEL for two subcatchments at Plynlimon, Wales is described. Conservative chemical mixing within mobile and immobile stores has been added to the hydrological model in an attempt to simulate observed stream chloride concentrations. The model was not fully able to simulate the observed behaviour, in particular the short‐ to medium‐term dynamics. One of the primary problems highlighted by the study was the representation of dry deposition and cloud‐droplet‐deposited chloride, which formed a significant part of the long‐term chloride mass budget. Equifinality of parameter sets inhibited the ability to determine the effective catchment mixing volumes and coefficients or the most likely partition between occult mass inputs and chloride mass inputs determined by catchment immobile‐store antecedent conditions. Some success was achieved, in as much as some aspects of the dynamic behaviour of the signal were satisfactorily simulated, although spectral analysis showed that the model could not fully reproduce the 1/f power spectra of observed stream chloride concentrations with its implications of a wide distribution of residence times for water in the catchment. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Pleistocene sediments,soils and landscape evolution at Stebbing,Essex     

Colin A. Whiteman  Rob A. Kemp 《第四纪科学杂志》1990,5(2):145-161

Pleistocene sediments and soils exposed at Stebbing in central Essex, England are described, analysed and interpreted. The sand and gravel units above Eocene London Clay and Upper Pliocene Red Crag are shown to be a high level member of the Kesgrave Formation, with a surface immediately beneath that of the Westland Green Gravels, which are tentatively assigned to the Pre-Pastonian ‘a’ Stage of the British Quaternary succession. The rubified, argillic soil developed in the surface of these fluvial deposits is a composite of the Valley Farm and Barham Soils and displays micromorphological evidence of several phases of clay illuviation, gleying and clay coating disruption. Originally truncated and buried beneath Anglian gelifluction deposits, cover sand and till, the soil has been exhumed in most places by subsequent erosion. The full succession, however, is preserved within large gulls that formed by periglacial cambering prior to this erosion. More recent loess incorporation and pedogenesis have modified the exhumed soil and the materials within the gulls.  相似文献   

The Loch Lomond Readvance on north Arran,Scotland: glacier reconstruction and palaeoclimatic implications     

Colin K. Ballantyne 《第四纪科学杂志》2007,22(4):343-359

Geomorphological mapping of northern Arran provides evidence for two advances of locally nourished glaciers, the younger being attributable to the Loch Lomond Stade (LLS) of ca. 12.9–11.5 k yr BP, primarily through the mutually exclusive relationship between glacial limits and Lateglacial periglacial features. The age of the earlier advance is unknown. Inferred LLS glacier cover comprised two small icefields and eight small corrie or valley glaciers and totalled 11.1 km². ELAs reconstructed using area–altitude balance ratio methods range from 268 m to 631 m for individual glaciers, with an area‐weighted mean ELA of 371 m. ELAs of individual glaciers are strongly related to snow‐contributing areas. The area‐weighted mean ELA is consistent with a north–south decline in LLS ELAs along the west coast of Great Britain. This decline has an average latitudinal gradient of 70 m 100 km^?1, equivalent to a mean southwards ablation‐season temperature increase of ca. 0.42°C 100 km^?1. Mean June–August temperatures at the regional climatic ELA, estimated from chironomid assemblages in SE Scotland, lay between 5.7 ± 0.1°C and 4.1 ± 0.2°C. Empirical relationships between temperature and precipitation at modern glacier ELAs indicate equivalent mean annual precipitation at the ELA lay between 2002 ± 490 mm and 2615 ± 449 mm. These figures suggest that stadial precipitation on Arran fell within a range between +8% and ?33% of present mean annual precipitation. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献