Partition coefficients for olivine-melt and orthopyroxene-melt systems     

Paul Beattie  Clifford Ford  Douglas Russel 《Contributions to Mineralogy and Petrology》1993,114(2):288-288

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A comparison of two methods of estimating transpiration rates from a Sitka spruce plantation     

R. Milne  J. D. Deans  E. D. Ford  P. G. Jarvis  J. Leverenz  D. Whitehead 《Boundary-Layer Meteorology》1985,32(2):155-175

Estimates of hourly transpiration from a 16–17 yr old Sitka spruce forest were calculated from the Penman-Monteith combination equation and compared with estimates from an eddy correlation/energy balance method.Canopy conductances were estimated from stomatal conductances measured using null balance diffusion porometers and took account of canopy variations of stomatal conductance and needle area index.Vertical heat fluxes were measured by the eddy correlation method; transpiration fluxes were then estimated from an energy balance of the forest.There was not a 1:1 relationship between the estimates of transpiration from the two methods. The major sources of error were concluded to be (i) difficulties of estimating the variation in stomatal conductance and leaf area through the canopy, (ii) errors in the value of total leaf area index, and (iii) errors in stomatal conductance measurements.The eddy correlation method was suggested as the more useful for future studies of the variation of forest transpiration in time or space, because the Penman-Monteith equation requires extensive biological measurements.  相似文献   

Field meetings to the Western USA 1981 & 1982     

K.L. Duff  T.D. Ford 《Proceedings of the Geologists' Association. Geologists' Association》1984,95(2):97-148

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Rapid entrenchment of stream profiles in the salt caves of Mount Sedom,Israel     

Amos Frumkin  Derek C. Ford 《地球表面变化过程与地形》1995,20(2):139-152

Rock salt is approximately 1000 times more soluble than limestone and thus displays high rates of geomorphic evolution. Cave stream channel profiles and downcutting rates were studied in the Mount Sedom salt diapir, Dead Sea rift valley, Israel. Although the area is very arid (mean annual rainfall ≈ 50 mm), the diapir contains extensive karst systems of Holocene age. In the standard cave profile a vertical shaft at the upstream end diverts water from a surface channel in anhydrite or clastic cap rocks into the subsurface route in the salt. Mass balance calculations in a sample cave passage yielded downcutting rates of 0–2 mm s^?1 during peak flood conditions, or about eight orders of magnitude higher than reported rates in any limestone cave streams. However, in the arid climate of Mount Sedom floods have a low recurrence interval with the consequence that long-term mean downcutting rates are lower: an average rate of 8·8 mm a^?1 was measured for the period 1986–1991 in the same sample passage. Quite independently, long-term mean rates of 6·2mm a^?1 are deduced from ¹⁴C ages of driftwood found in upper levels of 12 cave passages. These are at least three orders of magnitude higher than rates established for limestone caves. Salt cave passages develop in two main stages: (1) an early stage characterized by high downcutting rates into the rock salt bed, and steep passage gradients; (2) a mature stage characterized by lower downcutting rates, with establishment of a subhorizontal stream bed armoured with alluvial detritus. In this mature stage downcutting rates are controlled by the uplift rate of the Mount Sedom diapir and changes of the level of the Dead Sea. Passages may also aggrade. These fast-developing salt stream channels may serve as full-scale models for slower developing systems such as limestone canyons.  相似文献   

Rates of cave and landform development in the Yorkshire Dales from speleothem age data     

Melvyn Gascoyne  Derek C. Ford  Henry P. Schwarcz 《地球表面变化过程与地形》1983,8(6):557-568

Uranium-series ages have been obtained for 87 speleothems collected from nine major cave systems in the Craven district of northern England. Large systems such as Ease Gill Caverns, the West Kingsdale caves, and Gaping Gill-Ingleborough Cave, which contain relict high-level tunnels, are found to be older than 350,000 years (the limit of the ²³⁰Th/²³⁴U dating method). There is little evidence to indicate a significant enlargement of these passages since this time. Estimates of the age of Victoria Cave from ²³⁴U/²³⁸U isotopic ratios suggest that the cave has been fully relict for more than 500,000 years. Ages of in situ speleothems immediately adjacent to local base level cave streams show that mean maximum downcutting rates in limestone channels are about 2 to 5 cm 1000 yr. These rates are significantly lower than those obtained from direct measurements on limestone bedrock in stream channels but are comparable to areal denudation rates based on solute budgets. Using the present elevation of caves with respect to adjacent valley floor levels, mean maximum valley entrenchment rates are found to range between 5 cm/ky and < 20cm/ky, which corresponds to 6 m to < 24 m of lowering per glacial/interglacial cycle. These rates suggest that upper beds of the limestone were incised to form the Yorkshire Dales between 1 and 2 million years ago. The results indicate that the erosional effects of individual glaciations are not as severe as previously proposed in the literature.  相似文献   

Holistic environmental assessment and offshore oil field exploration and production     

Salter E  Ford J 《Marine pollution bulletin》2001,42(1):45-58

According to UK Government surveys, concern for the environment is growing. Environmental regulation of the industry is becoming wider in its scope and tougher in its implementation. Various techniques are available to assess how the industry can drive down its environmental impact and comply with environmental regulation. Environmental Assessments (EA) required by European law do not cover the whole life cycle of the project that they are analysing. Life Cycle Analysis (LCA) was developed to assess the environmental loadings of a product, process or activity over its entire life cycle. It was the first technique used in environmental analysis that adopted what was described as a holistic approach. It fails this approach by not assessing accidental emissions or environmental impacts other than those that are direct. Cost Benefit Analysis (CBA) offers the opportunity to value environmental effects and appraise a project on the basis of costs and benefits. Not all environmental effects can be valued and of those that can there is considerable uncertainty in their valuation and occurrence. CBA cannot satisfactorily measure the total environmental risk of a project. Consequently there is a need for a technique that overcomes the failures of project-level EA, LCA and CBA, and assesses total environmental risk. Many organizations such as, the British Medical Association, the European Oilfield Speciality Chemicals Association, the Royal Ministry of Petroleum and Energy (Norway) and Shell Expro now recognize that a holistic approach is an integral part of assessing total risk. The Brent SPAR case study highlights the interdisciplinary nature required of any environmental analysis. Holistic Environmental Assessment is recommended as such an environmental analysis.  相似文献   

The potential impact of herbivores on the susceptibility of the marsh plantSagittaria lancifolia to saltwater intrusion in coastal wetlands     

James B. Grace  Mark A. Ford 《Estuaries and Coasts》1996,19(1):13-20

The objective of this study was to experimentally evaluate the effects of simulated herbivory on the ability of a freshwater marsh plant to recover from temporary saltwater intrusion such as can be caused by tropical storms. Sods containingSagittaria lancifolia, a dominant plant in interior coastal marshes, were manipulated in the field so as to subject plants to a pulse of 15‰ salt water for a duration of 1 wk. In addition to the exposure to salt water, some plants were also subjected to both short-term and long-term flooding treatments of 20 cm, and to simulated herbivory (clipping). Following exposure to salt water, plants were allowed to recover over the winter and were harvested the next June. Neither simulated herbivory, nor salinity, nor flooding caused any long-term effect either singly or in pairwise combinations. However, when plants were subjected to herbivory, salt water, and flooding simultaneously, reduced growth and plant death occurred. These results suggest that high levels of grazing by herbivores may increase the susceptibility of coastal marsh plants to damage from saltwater intrusion. *** DIRECT SUPPORT *** A01BY073 00002  相似文献   

Field Meeting: The economic geology of the Peak District: 30 June – 2 July 1978     

T.D. Ford 《Proceedings of the Geologists' Association. Geologists' Association》1980,91(3):229-234

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A simulation study of the development of rillenkarren     

J. R. Glew  D. C. Ford 《地球表面变化过程与地形》1980,5(1):25-36

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Stable isotope studies of fluid inclusions in speleothems and their paleoclimatic significance     

Henry P Schwarcz  Russell S Harmon  Peter Thompson  Derek C Ford 《Geochimica et cosmochimica acta》1976,40(6):657-665

Fluid inclusions found trapped in speleothems (cave deposited travertine) are interpreted as samples of seepage water from which enclosing calcium carbonate was deposited. The inclusions are assumed to have preserved their D/H ratios since the time of deposition. Initial ¹⁸O/¹⁶O ratios can be inferred from δD because rain- and snow-derived seepage waters fall on the meteoric water line (δD = 8δ¹⁸O + 10). Estimates of temperature of deposition of the carbonate can be calculated from inclusion D/H ratios and δ¹⁸O of enclosing calcite in Pleistocene speleothems. For most speleothems investigated (0–200,000 yr old) δ¹⁸O of calcite appears to have decreased with increasing temperature of deposition indicating that the dominant cause of climate-dependent change in δ¹⁸O of calcite was the change in K_cw, the isotope fractionation equilibrium constant, with temperature; δ¹⁸O of meteoric precipitation generally increased with increasing temperature, but not sufficiently to compensate for the decrease in K_cw.  相似文献