Responses of arid and semiarid watersheds to increasing carbon dioxide and climate change as shown by simulation studies   总被引：1，自引：0，他引：1  

J. W. Skiles  Jon D. Hanson 《Climatic change》1994,26(4):377-397

The atmospheric concentration of carbon dioxide is expected to double in the next century causing increased temperatures and decreasing precipitation in some regions of the U.S. The increase in CO₂ will also directly affect stomatal conductance of plants. At the first-order watershed scale, changes in evaporative demand, transpiration, and runoff will also occur. Previous modeling studies of the effect of increased CO₂ on the water budgets of watersheds have been single-factor exercises where a single parameter representing stomatal conductance was reduced and the results noted. After showing validation results of the hydrology module, we used a comprehensive ecosystem model to examine the consequences of changes in precipitation, temperature, and CO₂-induced plant-function characteristics on small-basin runoff. As a result of the complex interactions and of the compensatory mechanisms simulated by the model, we conclude that for arid and semiarid watersheds of the western United States, there will be little change or an actual decrease in surface runoff because of increased CO₂ and climate change. This is due to the decrease in precipitation imposed on the model simulations. Implementing stomatal closure in the model did not increase runoff from the watersheds when temperatures were increased and precipitation decreased.  相似文献   

Preliminary study of the redistribution and transformation of HgS from cinnabar mine tailings deposited in Honda Bay, Palawan, Philippines     

Gaboury Benoit  Jon M. Schwantes  Gil S. Jacinto  Margaret R. Goud-Collins 《Marine pollution bulletin》1994,28(12):754-759

Mining operations in Palawan, Philippines, resulted in cinnabar (HgS) mine tailings being used to build a 600 m long peninsula in Honda Bay. Samples collected from the peninsula as well as sediments from the surrounding waters had elevated mercury levels as high as 570 ppm. Natural processes are transporting mercury as much as 10 km from the peninsula, mainly in a coastwise direction, and preferentially associated with fine-grained, organic-rich sediments. Depth of penetration into sediments exceeds 10 cm near the source. As the HgS is transported away from the peninsula, it is rapidly altered to more bioavailable forms; 50% conversion occurs within a distance of only 10–40 m.  相似文献   

Water quality, phosphorus input reductions, analytical methods and lake internal/self-purification measures: A case study of lake Frøylandsvatn, Norway     

Jon Lasse Bratli 《Marine pollution bulletin》1994,29(6-12):435-438

Lake Frøylandsvatn is a shallow eutrophic lake which has frequent blooms of various species of blue-green algae, often producing toxins. The lake receives heavy nutrient loads, mainly from agriculture, as well as a large internal load from its own sediments. It also shows several signs of being an unbalanced ecosystem. It has been calculated that phosphorus and chlorophyll levels need to be reduced by approximately 50% to improve the water quality enough for swimming. The analysis presented here makes it possible to compare the cost-effectiveness of different measures, including both catchment area and lake-internal methods. In addition to conventional means of reducing phosphorus pollution caused by agricultural activities and sewage, other measures, including biomanipulation and self-purification processes through artificial ponds and wetlands, will be necessary to achieve the ambitious goal that has been set.  相似文献   

The effect of the seawater cooling system of a nuclear generating station on the growth of mussels in experimental populations     

Jon Kastendiek  Stephen C. Schroeter  John Dixon 《Marine pollution bulletin》1981,12(12):402-407

In order to determine the effects of the effluent of a nuclear generating station on the growth of mussels, replicate experimental populations of Mytilus edulis were suspended from buoys located various distances upcoast and downcoast from the outfall of the cooling system and from buoys in a control area 13 km downcoast. Experiments were conducted for periods of one, two, and four months when the plant was pumping heated effluent and for similar periods when the pumps were operating intermittently and the effluent was not heated. Significant positive linear trends of growth with distance from the outfall were observed during all experiments. In contrast, a significant relationship of growth relative to the origin of the array of stations at the control site was observed only once. These results demonstrate that the cooling system caused a decrease in the growth of mussels in the vicinity of the outfall, and that factors other than heat were responsible for this reduced growth.  相似文献   

Rare-earth element fractionation and petrogenetic modelling in charnockitic rocks,southwest Norway     

Jon Steen Petersen 《Contributions to Mineralogy and Petrology》1980,73(2):161-172

Quantitative analysis of REE distribution in differentiated, clearly intrusive charnockites from southwest Norway, reveal extreme variation in both absolute abundances and fractionation patterns. The pyroxene-bearing, charnockitic facies show uniform REE patterns with slight enrichment of the light-REE (about 150x chondrites) and positive, neutral or negative Eu-anomalies. Subsequent amphibole-bearing, adamellitic facies show progressive, preferential enrichment of light-REE, reaching La-values higher than 500x chondrites, and increasingly negative Euanomalies. Finally, highly differentiated biotite-granites show a marked depletion of ight-REE, ending with chondrite-normalized La/Lu ratios about 1 and Eu/ Eu^* ratios less than 0.2.Using geochemical model calculation, relating major element variations between three main stages of differentiation in terms of refractory mineral assemblages, stepwise quantitative modelling of the REE distributions reproduces the observed changes, and support an origin of the charnockite series as progressively fractionated residual liquids.Close similarity with the REE patterns of charnockite-rapakivi suites elsewhere implies that these may constitute a series of co-magmatic rocks, derived from related more basic source magmas. The fact that the least differentiated members of the series, the charnockites, generally display remarkably uniform REE-patterns, suggests that they equilibrated with a refractory crystal fraction that produces a uniform, bulk partition coefficient. The present analysis suggests that this would be plagioclase and orthopyroxene in a ratio of about 41 and including minor apatite, which in turn points towards affinity with potentially plagioclase-rich cumulates.  相似文献   

Coral growth rate: Variation with depth     

Paul A. Baker  Jon N. Weber 《Earth and Planetary Science Letters》1975,27(1):57-61

Light and temperature are two of the most important physical factors affecting rates of growth of reef corals. The effect of light has been determined by X-radiographic measurement of long-term growth rates for 89 colonies of the coralMontastrea annularis collected over a 27.5-m depth range from St. Croix, U.S. Virgin Islands. These measurements, in conjunction with measurements of skeletal density, have established thatM. annularis calcifies most rapidly at intermediate depths, and they have confirmed the identification of two distinct populations within this important frame-building species.  相似文献   

Xxth International Congress of Photogrammetry and Remote Sensing     

Paul R. T. Newby  Peter A. Woodsford  Jon P. Mills  David A. Holland  William Tompkinson  Adrian J. Holmes  Stuart Robson  Paul Aplin  Simon J. Buckley  Henny Mehner 《The Photogrammetric Record》2004,19(108):375-402

The XXth International Congress of Photogrammetry and Remote Sensing was held at the Istanbul Convention and Exhibition Centre (ICEC), Turkey, from 12th to 23rd July 2004. Reports are given on the Congress as a whole, including the General Assembly, some Technical Commission activities and the Congress Exhibition. Papers from the Congress are published in Volume XXXV of the International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences.  相似文献   

Green hope or greenwash? The actions of the European Union at the World Summit on sustainable development     

Simon Lightfoot  Jon Burchell   《Global Environmental Change》2004,14(4):73

This article examines whether the European Union (EU) could be seen as a normative power at the recent World Summit on Sustainable Development. We explain how the EU operationalised its commitment to the concept of sustainable development before highlighting the impact the EU had on the final summit outcomes. It shows that although in many areas the EU was able to offer leadership, internal policy coherence prevented it fully being able to develop that role and thus fully promoting the norm of sustainable development.  相似文献   

Correlation and dating of Quaternary alluvial-fan surfaces using scarp diffusion     

Leslie Hsu  Jon D. Pelletier 《Geomorphology》2004,60(3-4):319-335

Great interest has recently been focused on dating and interpreting alluvial-fan surfaces. As a complement to the radiometric methods often used for surface-exposure dating, this paper illustrates a rapid method for correlating and dating fan surfaces using the cross-sectional shape of gullies incised into fan surfaces. The method applies a linear hillslope-diffusion model to invert for the diffusivity age, κt (m²), using an elevation profile or gradient (slope) profile. Gullies near the distal end of fan surfaces are assumed to form quickly following fan entrenchment. Scarps adjacent to these gullies provide a measure of age. The method is illustrated on fan surfaces with ages of approximately 10 ka to 1.2 Ma in the arid southwestern United States. Two areas of focus are Death Valley, California, and the Ajo Mountains piedmont, Arizona. Gully-profile morphology is measured in two ways: by photometrically derived gradient (slope) profiles and by ground-surveyed elevation profiles. The κt values determined using ground-surveyed profiles are more consistent than those determined using photo-derived κt values. However, the mean κt values of both methods are comparable. The photometric method provides an efficient way to quantitatively and objectively correlate and relatively-date alluvial-fan surfaces. The κt values for each surface are determined to approximately 30–50% accuracy.  相似文献   

Chemical studies of L chondrites. VI: variations with petrographic type and shock-loading among equilibrated falls     

Jon M Friedrich  John C Bridges  Ming-Sheng Wang 《Geochimica et cosmochimica acta》2004,68(13):2889-2904

To study compositional trends associated with open and closed system metamorphism and/or shock-induced heating of the L4-6 chondrite parent(s), we used ICPMS and RNAA to quantify 51 trace elements in 48 chemically representative fall samples. With these data, we used graphic and two multivariate statistical methods for examining evidence for compositional differences with respect to petrographic type and degree of shock loading. Comparisons of mildly shocked (S1-S3) L5 and L6 suites (9 and 8 chondrites, respectively) yield no convincing statistical evidence for a difference in trace element content. Our multivariate comparisons show a difference on a model-dependent basis, but yield indeterminate results on a model-independent basis. Compositionally, suites of strongly shocked (S4-S6) and mildly shocked L4-6 chondrites (26 and 19 samples, respectively) can be distinguished at statistically significant levels on both model-dependent and -independent bases. In the strongly shocked suite, contents of refractory lithophiles are higher, and siderophiles and volatiles are lower than those of the mildly shocked suite at moderately (p ≤ 0.05) to highly significant (p ≤ 0.01) levels. Our studies suggest that chemical differences from vaporization and loss of volatiles along with metal/silicate partitioning are present from extended cooling of shock-heated bodies produced by intermittent impacts, especially the massive impact(s) that disrupted the L chondrite parent(s) ∼500 Ma ago.  相似文献