Changes in Soybean Yields in the Midwestern United States as a Result of Future Changes in Climate, Climate Variability, and CO2 Fertilization     

Jane Southworth  R. A. Pfeifer  M. Habeck  J. C. Randolph  O. C. Doering  J. J. Johnston  D. G. Rao 《Climatic change》2002,53(4):447-475

This modeling study addresses the potential impacts of climate change and changing climate variability due to increased atmospheric CO₂ concentration on soybean (Glycine max (L.) Merrill) yields in theMidwestern Great Lakes Region. Nine representative farm locations and six future climate scenarios were analyzed using the crop growth model SOYGRO. Under the future climate scenarios earlierplanting dates produced soybean yield increases of up to 120% above current levels in the central and northern areas of the study region. In the southern areas, comparatively small increases (0.1 to 20%) and small decreases (–0.1 to–25%) in yield are found. The decreases in yield occurred under the Hadley Center greenhouse gas run (HadCM2-GHG), representing a greater warming, and the doubled climate variability scenario – a more extreme and variableclimate. Optimum planting dates become later in the southern regions. CO₂fertilization effects (555 ppmv) are found to be significant for soybean, increasing yields around 20% under future climate scenarios.For the study region as a whole the climate changes modeled in this research would have an overall beneficial effect, with mean soybean yield increases of 40% over current levels.  相似文献   

Importance of Nonequilibrium Sorption Conditions: Contaminated Soil     

Daniel R. Opdyke  Raymond C. Loehr 《Ground Water Monitoring & Remediation》2002,22(3):136-143

When modeling the fate and transport of chemicals in ground water, a common assumption is that sorption equilibrium is achieved rapidly. This local equilibrium assumption is valid when the rate of chemical sorption to soil particles is more rapid than the rate of aqueous chemical change by other processes. However, for some chemicals (e.g., weathered hydrocarbons) this assumption is not necessarily correct. As a result, an increasing body of knowledge related to the extent and rate of release (ROR) of hydrocarbons from soil has been generated.
When evaluating site remediation options, it is important to know when nonequilibrium sorption conditions may have a significant impact on such decisions. In this study, a tiered procedure was developed to consistently evaluate the importance of ROR information at a site. The procedure consists of three tiers, each requiring more information and computational effort than the previous one. The first tier employs three power-law relationships between site parameters and the importance of ROR kinetics to quickly and easily estimate the importance of ROR information at a site. The second tier involves running and evaluating the deterministic component of a ground water fate and transport model. The third tier involves running and evaluating the probabilistic component of the ground water model. Given the sequential nature of the procedure, it is not necessary to perform Tier II (or Tier III) unless the Tier I (or Tier II) evaluation indicates that ROR kinetics may be important at the specific site under consideration. An example of applying the Tier I analysis to a specific site is provided. The results illustrate the influence of the chemical removal processes (e.g., advection and biodegradation) on the predicted importance of ROR kinetics. For the site considered, ROR kinetics had an important impact on model predictions when the biodegradation rate was high.  相似文献   

Lead in the Bolsa wetland of southern California, USA: Effect of flood control channelization     

Raymond Z. Riznyk  Gail A. Mason 《Marine pollution bulletin》1979,10(12):349-351

The distribution of lead in sediments of an estuary receiving flood control discharge has been examined. Relatively high concentrations of lead with a mean value of 64 ppm were found within the outer portion of Bolsa Bay which receives flood control runoff. Significantly lower concentrations of lead with a mean value of 9 ppm were found within the impounded inner portion of the bay which does not receive flood control discharge. On the basis of our findings we recommend that flood control runoff no longer be discharged directly into estuaries but that discharge be either rerouted to ocean outfalls or reclaimed and used for agricultural and industrial purposes.  相似文献   

Dissolution kinetics and the weathering of mafic minerals     

Raymond Siever  Norma Woodford 《Geochimica et cosmochimica acta》1979,43(5):717-724

Fayalite, hypersthene, basalt, and obsidian were dissolved in buffered solutions (25°C; pH 4.5 and 5.5) under air, N₂ or O₂ atmospheres, in order to follow the kinetics of dissolution. Each dissolved more rapidly at lower pH values, dissolving most rapidly in the initial few days, followed by slower dissolution for periods up to six months. Dissolution was more rapid when air was excluded. In oxygen atmospheres an Fe(OH)₃ precipitate armors mineral surfaces, thus inhibiting further dissolution, and further affects the solution by scavenging dissolved silica and cations. Dissolution reactions include initial exchange between cations and H⁺, incongruent dissolution of silicate structures, oxidation of Fe²⁺ in solution, precipitation of Fe(OH)₃, and scavenging of dissolved silica and cations by Fe(OH)₃. Dissolution kinetics may explain weathering of mafic rocks and minerals at the Earth's surface, the formation of Fe-oxide coatings on mineral grains, weathering of submarine mafic rocks and intrastratal solution of mafic minerals in buried sandstones. Early Precambrian weathering would have been more rapid before the appearance of large amounts of oxygen in the atmosphere, and continental denudation rates may have been higher than at present because of this effect and the predominance of mafic igneous rocks at an early stage of continent formation and growth.  相似文献   

Genetic variation in two populations of blue crab,Callinectes sapidus     

Marthe A. Cole  Raymond P. Morgan 《Estuaries and Coasts》1978,1(3):202-205

Genetic variability of the blue crab,Callinectes sapidus, was estimated for populations in Chesapeake and Chincoteague Bays. Genetic similarity between these populations was attributed to larval intermixing in the mid-Atlantic Bight.  相似文献   

The Pyrenees: Subduction and collision?     

Gilbert Boillot  Raymond Capdevila 《Earth and Planetary Science Letters》1977,35(1):151-160

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Rare earth element investigation of the Cliefden Outcrop,N.S.W., Australia     

Phillip L. Hellman  Raymond E. Smith  Paul Henderson 《Contributions to Mineralogy and Petrology》1977,65(2):155-164

The effect of low grade hydrous burial metamorphism (prehnite-pumpellyite facies) upon the rare earth elements (REE) has been studied by using samples from the Cliefden Outcrop, New South Wales. The REE, together with other reputedly immobile elements, have been mobilised during the metamorphism. Although mobile, the REE have behaved remarkably coherently with little light rare earth (LREE) fractionation. This is reflected in the chondrite normalised patterns which are sub-parallel to parallel in shape. High correlations of REE with other elements can be used to predict the maximum likely variation of these elements in the studied outcrop. The high correlations do not necessarily mean that, for similarly metamorphosed terrains, crystallisation-differentiation processes have operated but may rather have resulted from strong geochemical coherence during post-crystallisation elemental redistribution. The REE do not appear to be strongly domain controlled within the Cliefden Outcrop.  相似文献   

Underground Storage Tank Monitoring: Observation Well Based Systems     

Raymond A. Scheinfeld  John B. Robertson  Todd G. Schwendeman 《Ground Water Monitoring & Remediation》1986,6(4):49-55

A growing number of state and local governments and petroleum-related companies require the use of release detection systems for underground petroleum storage tanks. This has resulted in a confusing array of commercially available petroleum product detection devices, many of which have not been extensively field-tested. These systems, which are installed in ground water observation wells, vapor wells or U-tubes, include hydrocarbon-detecting paste, bailers, interface probes, electrical resistivity sensors, thermal-conductivity sensors, hydrocarbon-soluble devices, hydrocarbon-permeable materials and vapor detectors. This paper describes the available state-of-the-art technology for leak detection and the application for which each system is best suited.  相似文献   

Experimental ‘syntectonic’ hydration of basalt     

E.H Rutter  C.J Peach  S.H White  D Johnston 《Journal of Structural Geology》1985,7(2):251-266

This paper outlines in general terms the role of metamorphic transformations during rock deformation. Long duration, triaxial stress relaxation tests at 600°C. 160 MPa confining pressure on wet crushed basalt, sheared in sawcuts made in intact basalt cylinders are reported. Mechanical data are interpreted in terms of a material which shows a small strain-rate sensitivity to large variations in applied stress, but which work hardens dramatically as a result of marked microstructural changes which occur during straining. Permanent distortions of c. 20% were produced in the samples.Tests at 100 MPa pore-water pressure resulted in the formation of oriented overgrowths of amphibole, preferentially developed on less stressed interfaces between original grains and in pore spaces. Substantial redistribution of feldspar also occurred. At low pore pressures no amphibole formed and only feldspar was recrystallized. Much of the original porosity of the rock was eliminated in all cases.The mechanical and microstructural data are interpreted in terms of flow by some combination of grain sliding and diffusional accommodation, with the reprecipitated, diffused material being the product of a chemical reaction involving all original solid phases plus water. From a consideration of the effects of the reaction on the chemical potential gradients driving diffusion, it is concluded that although the syntectonic hydration exerts a profound effect on the microstructural and mineralogical development of the rock during deformation, there is no substantial enhancement of the rate of strain.Similar microstructural developments also occur in natural rocks deformed during retrogressive metamorphic events, and examples are described for comparison.  相似文献   

A magnetic method for determining the geometry of hydraulic fractures     

J. D. Byerlee  M. J. S. Johnston 《Pure and Applied Geophysics》1976,114(3):425-433

Summary We propose a method that may be used to determine the spatial orientation of the fracture plane developed during hydraulic fracture. In the method, magnetic particles are injected into the crack with the fracturing fluid so as to generate a sheet of magnetized material. Since the magnetization of a body with extreme dimension ratios, such as a crack, exceeds that of an equidimensional body and since this magnetization is sensitive both to orientation and geometry, this could be used to obtain information about the crack. By measuring the vertical and horizontal components of the magnetic field and field gradients at the earth's surface surrounding the injection well with superconducting magnetometers having 10^–4 gamma sensitivity and also by measuring field direction within the well itself, it should be possible to calculate the orientation and perhaps infer the approximate geometry of the fracture surface. Experiments on electric field potential operated in conjunction with this experiment could further constrain estimates of shape and orientation.  相似文献