Sheet flow in a salt-marsh basin,North Inlet,South Carolina     

Jerry L. Miller  L. R. Gardner 《Estuaries and Coasts》1981,4(3):234-237

The magnitude of sheet flow in a small South Carolina salt marsh was evaluated by comparing the storage curve for the basin based on topographic data with that based on current measurements in the main channel. The results indicate that on spring tides more than 50% of the volume of water that enters the basin enters as sheet flow over the grassy flats of the marsh. The current data also suggest that the actual storage curve may be a hysteresis loop with separate flood and ebb segments.  相似文献   

Composition and vertical flux of organic matter in a large Alaskan estuary     

Alexander J. Chester  Jerry D. Larrance 《Estuaries and Coasts》1981,4(1):42-52

Observations of the composition and rate of input of organic matter to the sea floor were made at three locations in lower Cook Inlet, Alaska, during five cruises taken in the spring and summer of 1978. Total particulate, plant pigment, carbon, nitrogen, fecal pellet, and phytoplankton cell fluxes, inferred from sediment trap samples, were related to algal biomass and production in overlying waters. A daily average of 7.5% of the phytoplankton biomass was lost to the bottom. Of this loss, 83% was attributable to zooplankton grazing and fecal pellet production. At the three sampling sites, an average of 39 g C m^?2 (range of 17–60 g C m^?2, was sedimented to the bottom between May and August. This carbon flux represented an average of 12% of the total primary production measured for that time period. Kachemak Bay eastern arm of the inlet, is identified as an extremely productive embayment in which large amounts of organic matter were transferred to the sea floor.  相似文献   

Benthonic foraminiferal faunal and isotopic data for the postglacial evolution of the Champlain Sea     

Bruce H. Corliss  Allen S. Hunt  Lloyd D. Keigwin  Jr. 《Quaternary Research》1982,17(3):325-338

Benthonic foraminiferal faunal and isotopic data from Champlain Sea sediments (approximately 12,500 to 10,000 yr B.P. in age) in two piston cores from Lake Champlain provide a detailed, apparently continuous record of the evolution of the Champlain Sea. Cassidulina reniforme and Islandiella helenae are the dominant benthonic foraminifera during the initial phase of the Champlain Sea, and are replaced by Elphidium excavatum forma clavatum and Protelphidium orbiculare as the dominant species during the remainder of the sea's history. The oxygen-isotopic data show a gradual decrease in δ¹⁸O between approximately 12,500 and 10,900 yr B.P., followed by a more rapid decrease during the interval 10,900 to 10,000 yr B.P. The δ¹³C data have a similar trend as δ¹⁸O, with generally decreasing values up the section. The isotopic and faunal data suggest that nearly marine conditions were present in the initial plase of the Champlain Sea, followed by gradually decreasing salinities and increasing temperatures as the sea evolved. The beginning of the rapid isotopic decrease at approximately 10,900 yr B.P. marks the onset of the largest environmental change in the history of the Champlain Sea, probably reflecting a major pulse of meltwater from the Laurentide Ice Sheet.  相似文献   

Relationships between organically bound Cu and Mn in settling particulate matter and biological processes in a subarctic estuary     

Richard A. Feely  Alexander J. Chester  Anthony J. Paulson  Jerry D. Larrance 《Estuaries and Coasts》1982,5(1):74-80

Plankton studies in Kachemak Bay, Alaska were combined with short-term sediment trap deployments in order to show the relationships of fluxes of Cu and Mn in organic particulate matter with biological processes occurring in the overlying water column. A large spring bloom decrease throughout the summer, due to decreasing nutrient levels and increasing grazing pressure by zooplankton. The concentration of organically bound Cu and Mn in the sediment trap particulate material increased throughout the summer reaching a maximum in August while fecal pellet production exhibited a similar increase. The fluxes of total particulate matter and organic carbon reached a maximum in June and represented a 30% increase over the corresponding fluxes in May. In contrast, the fluxes of organically bound Cu and Mn and fecal pellets in August represented 200%, 360% and 760% increases, respectively, over their respective fluxes in May. These results suggest that the enrichment of Cu and Mn in the organic particulate matter during August was a result of bioaccumulation of these metals into fecal material. The increase in the flux of the organically bound metals indicates a strong coupling between biological processes in the water column and their vertical transport. Thus, the production and subsequent sinking of fecal pellets may govern the transport of trace metals to the underlying water column and may also govern the transfer of a primary source of food and its associated trace metals to benthic communities.  相似文献   

The inner city: In search of the problem     

Ray Forrest  John Lloyd  Nick Rogers  Peter Williams 《Geoforum》1979,10(1):109-116

This paper explores the theoretical content of the inner-city debate in Britain and seeks to examine the extent to which the ‘problem’ is either new or primarily economic. It is argued that the inner-city issue, while subject to specific political and ideological forces, is associated with the general processes of uneven capitalist development. In this sense, metropolitan decline is a further manifestation of the relationship between the built environment, the transience of economic activity and social change. More specifically the decline of the inner city relates to the incipient role of Britain in the development of capitalism and its current position in the world economy. The emergence of this as a ‘problem’ for the British state is combined with a convenient spatial determinism, which isolates the inner city as an anomaly even as the search for palliatives is erected to the status of a major social task.  相似文献   

Variations in carbon and oxygen isotope ratios as a possible guide to ore     

Lloyd Hamilton 《Mineralium Deposita》1968,3(1):81-84

Contour maps showing variations in carbon and oxygen isotope ratios may be useful as a guide to ore. Previous literature suggests that the isotopic composition of carbon is related to the environment in which it is deposited. Sedimentary syngenetic ore deposits are also related to the depositional environment in which they occur and should therefore be related to the isotopic composition of the carbon deposited along with the ore. Although metamorphism may obscure palaeontological and stratigraphic indicators of environment, the isotopic composition of organic carbon appears to be unaffected by it. Previous literature suggests that variations in oxygen isotopes can be used also as a guide to certain epigenetic ore deposits.

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Zusammenfassung Isotopenverteilungskarten sind nützliche Hilfsmittel bei der Erzprospektion. In der Literature wird auf die Abhängigkeit der Isotopen-Zusammensetzung vom Ablagerungsmilieu aufmerksam gemacht. Sedimentäre syngenetische Erzlagerstätten sind ohne Zweifel vom Ablagerungsmilieu abhängig. Es liegt deshalb nahe, die Isotopen-Zusammensetzung des darin enthaltenen Kohlenstoffs mit derjenigen der erzbildenden chemischen Elemente zu vergleichen. Obwohl metamorphe Prozesse paläontologische und stratigraphische Prozesse verwischen können, scheint die Isotopen-Zusammensetzung davon unbeeinflußt zu bleiben. Als Hilfsmittel können weiterhin die in der Literatur beschriebenen Isotopenverhältnisse des Sauerstoffs herangezogen werden.

  相似文献   

Solubility of crude oil in methane as a function of pressure and temperature     

Leigh C. Price  Lloyd M. Wenger  Tom Ging  Charles W. Blount 《Organic Geochemistry》1983,4(3-4)

The solubility of a 44° API (0.806 sp. gr.) whole crude oil has been measured in methane with water present at temperatures of 50 to 250°C and pressures of 740 to 14,852 psi, as have the solubilities of two high molecular weight petroleum distillation fractions at temperatures of 50 to 250°C and pressures of 4482 to 25,266 psi. Both increases in pressure and temperature increase the solubility of crude oil and petroleum distillation fractions in methane, the effect of pressure being greater than that of temperature. Unexpectedly high solubility levels (0.5–1.5 grams of oil per liter of methane—at laboratory temperature and pressure) were measured at moderate conditions (50–200°C and 5076–14504 psi). Similar results were found for the petroleum distillation fractions, one of which was the highest molecular weight material of petroleum (material boiling above 266°C at 6 microns pressure). Unexpectedly mild conditions (100°C and 15,200 psi; 200°C and 7513 psi) resulted in cosolubility of crude oil and methane. Under these conditions, samples of the gas-rich phase gave solubility values of 4 to 5 g/l, or greater.Qualitative analyses of the crude-oil solute samples showed that at low pressure and temperature equilibration conditions, the solute condensate would be enriched in C₅–C₁₅ range hydrocarbons and in saturated hydrocarbons in the C₁₅₊ fraction. With increases in temperature and especially pressure, these tendencies were reversed, and the solute condensate became identical to the starting crude oil.The data of this study, compared to that of previous studies, shows that methane, with water present, has a much greater carrying capacity for crude oil than in dry systems. The presence of water also drastically lowers the temperature and pressure conditions required for cosolubility.The data of this and/or previous studies demonstrate that the addition of carbon dioxide, ethane, propane, or butane to methane also has a strong positive effect on crude oil solubility, as does the presence of fine grained rocks.The n-paraffin distributions (as well as the overall composition) of the solute condensates are controlled by the temperature and pressure of solution and exsolution, as well as by the composition of the original starting material. It appears quite possible that primary migration by gaseous solution could ‘strip’ a source rock of crude-oil like components leaving behind a bitumen totally unlike the migrated crude oil. The data of this study demonstrate previous criticisms of primary petroleum migration by gas solution are invalid; that primary migration by gaseous solution cannot occur because methane cannot dissolve sufficient volumes of crude oil or cannot dissolve the highest molecular weight components of petroleum (tars and asphaltenes).  相似文献   

Increased accuracy of geostatistical prediction of nitrogen dioxide in the United Kingdom with secondary data     

C.D. Lloyd  P.M. Atkinson 《International Journal of Applied Earth Observation and Geoinformation》2004,5(4):293-305

Five techniques were used to map nitrogen dioxide (NO₂) concentrations in the United Kingdom. The methods used to predict from point data, collected as part of the UK NO₂ diffusion tube network, were local linear regression (LR), inverse distance weighting (IDW), ordinary kriging (OK), simple kriging with a locally varying mean (SKlm) and kriging with an external drift (KED). These techniques may be divided into two groups: (i) those that use only a single variable in the prediction process (IDW, OK) and (ii) those that make use of additional variables as a part of prediction (LR, SKlm and KED). Nitrous oxides emission data were used as secondary data with LR, SKlm and KED. It was concluded that SKlm provided the most accurate predictions based on the summary statistics of prediction errors from cross-validation.  相似文献   

Vulnerability of Island Tropical Montane Cloud Forests to Climate Change, with Special Reference to East Maui, Hawaii     

Lloyd L. Loope  Thomas W. Giambelluca 《Climatic change》1998,39(2-3):503-517

Island tropical montane cloud forests may be among the most sensitive of the world's ecosystems to global climate change. Measurements in and above a montane cloud forest on East Maui, Hawaii, document steep microclimatic gradients. Relatively small climate-driven shifts in patterns of atmospheric circulation are likely to trigger major local changes in rainfall, cloud cover, and humidity. Increased interannual variability in precipitation and hurricane incidence would provide additional stresses on island biota that are highly vulnerable to disturbance-related invasion of non-native species. Because of the exceptional sensitivity of these microclimates and forests to change, they may provide valuable listening posts for detecting the onset of human-induced global climate change.  相似文献   

Analysis of Nitrate-Nitrogen Movement Near High-Capacity Irrigation Wells     

Xunhong Chen  Jerry F. Ayers  David C. Gosselin 《Ground Water Monitoring & Remediation》1998,18(4):148-156

AGalerkin finite-element model coupled with a particle tracking routine was developed to analyze the flow and transport dynamics near a high-capacity irrigation well. The model was used to compute the head distribution around the pumping well, to determine the area of influence, and to define ground water flowlines during short-term pumping periods typical of those used to collect water quality samples from high-capacity wells. In addition to hypothetical example results, the model was used to qualitatively analyze data obtained from pump-and-sample experiments conducted in an unconfined alluvial aquifer within the Platte River valley of south-central Nebraska where nitrate-nitrogen (NO₃-N) contamination is prevalent.
Simulation results of both the hypothetical and field cases suggest that short-term pumping events, impact a limited volume of aquifer. The area of influence and flowlines are affected by aquifer anisotropy, pumping rate, and well construction characteristics). Ground water above or below the screened intervals does not enter a partially penetrating well in anisotropic aquifers. In aquifers where NO₃-N concentration varies vertically and horizontally, waler quality samples from an irrigation, or other high-capacity, well provide only limited information about ground water contamination. A numerical model is thus recommended for calculating the area of influence and determining flowlines around high-capacity wells so that information derived from water quality samples collected at the wellhead can be better interpreted.  相似文献