Skip to main content
Advanced Search

Filters: Tags: kinetics (X)

9 results (8ms)   

View Results as: JSON ATOM CSV
Reactions between CO2-charged brines and reservoir minerals might either enhance the long-term storage of CO2 in geological reservoirs or facilitate leakage by corroding cap rocks and fault seals. Modelling the progress of such reactions is frustrated by uncertainties in the absolute mineral surface reaction rates and the significance of other rate limiting steps in natural systems. Here we use the chemical evolution of groundwater from the Jurassic Navajo Sandstone, part of a leaking natural accumulation of CO2 at Green River, Utah, in the Colorado Plateau, USA, to place constraints on the rates and potential controlling mechanisms of the mineral–fluid reactions, under elevated CO2 pressures, in a natural system....
Phosphorus and nitrogen uptake capacities were assessed during 36–58 d drying cycles to determine whether the ability of sagebrush (Artemisia tridentata Nutt.) to absorb these nutrients changed as the roots were subjected to increasing levels of water stress. Water was withheld from mature plants in large (6 I) containers and the uptake capacity of excised roots in solution was determined as soil water potentials decreased from −0.03 MPa to −5.0 MPa. Phosphorus uptake rates of excised roots at given substrate concentrations increased as preharvest soil water potentials decreased to −5.0 MPa. Vmax and Km also increased as soil water potentials declined. Declining soil water potentials depressed nitrogen uptake...
The influences of spiked Zn concentrations (1-40 micromol/g) and equilibration time (approximately 95 d) on the partitioning of Zn between pore water (PW) and sediment were evaluated with estuarine sediments containing two levels (5 and 15 micromol/g) of acid volatile sulfides (AVS). Their influence on Zn bioavailability was also evaluated by a parallel, 10-d amphipod (Leptocheirus plumulosus) mortality test at 5, 20, and 85 d of equilibration. During the equilibration, AVS increased (up to twofold) with spiked Zn concentration ([Zn]), whereas Zn-simultaneously extracted metals ([SEM]; Zn with AVS) remained relatively constant. Concentrations of Zn in PW decreased most rapidly during the initial 30 d and by 11-...
Characterization of uptake and loss dynamics is critical to understanding risks associated with contaminant exposure in aquatic animals. Dynamics are especially important in addressing questions such as why coexisting species in nature accumulate different levels of a contaminant. Here we manipulated copper (Cu) stable isotopic ratios (as an alternative to radioisotopes) to describe for the first time Cu dynamics in a freshwater invertebrate, the bivalve Corbicula fluminea. In the laboratory, Corbicula uptake and loss rate constants were determined from an environmentally realistic waterborne exposure to 65Cu (5.7 microg L(-1)). That is, we spiked deionized water with Cu that was 99.4% 65Cu. Net tracer uptake was...
Numerous coal gasification studies have been found in the literature those employed various kinds of gasifying agents such as steam and carbon dioxide. These studies are featured with wide variations in the parametric conditions and the usage of equipments. Steam is frequently employed as a gasifying agent, however, in several studies carbon dioxide has also been used as a gasifying agent either pure or in combination with other gasifying agents (H2O, O2, CO, H2). This paper is a brief review of the coal gasification with CO2 as a diluent. Different factors were studied over the coal gasification with CO2 such as coal rank, pressure, temperature, gas composition, catalyst and the minerals present inside the coal,...
thumbnail
Two members of the Green River Formation in the Washakie Basin have been analysed by organic geochemical and organic petrographic techniques and the results placed in a sequence stratigraphic framework. One of these members, the Laney Shale, was deposited in a hydrologically closed, alkaline lake under an arid climate and was characterized by high concentrations of alginite-rich organic matter whereas the other, the Luman Tongue, was deposited in a hydrologically open, freshwater lake under a humid climate and consisted of organic-poor profundal lake mudstones and coaly lake margin sediments. Potential source rocks in both lake types have the potential for generating high-wax oil at high subsurface temperatures...
Chemical or mineralogical profiles in regolith display reaction fronts that document depletion of leachable elements or minerals. A generalized equation employing lumped parameters was derived to model such ubiquitously observed patterns: C = C 0 C 0 − C x = 0 C x = 0 exp ( Γ ini · k ˆ · x ) + 1 Here C, Cx = 0, and Co are the concentrations of an element at a given depth x, at the top of the reaction front, or in parent respectively. Γini is the roughness of the dissolving mineral in the parent and k̂ˆ is a lumped kinetic parameter. This kinetic parameter is an inverse function of the porefluid advective velocity and a direct function of the dissolution rate constant times mineral surface area per unit volume regolith....
The influences of spiked Zn concentrations (1-40 micromol/g) and equilibration time (approximately 95 d) on the partitioning of Zn between pore water (PW) and sediment were evaluated with estuarine sediments containing two levels (5 and 15 micromol/g) of acid volatile sulfides (AVS). Their influence on Zn bioavailability was also evaluated by a parallel, 10-d amphipod (Leptocheirus plumulosus) mortality test at 5, 20, and 85 d of equilibration. During the equilibration, AVS increased (up to twofold) with spiked Zn concentration ([Zn]), whereas Zn-simultaneously extracted metals ([SEM]; Zn with AVS) remained relatively constant. Concentrations of Zn in PW decreased most rapidly during the initial 30 d and by 11-...


    map background search result map search result map Organic geochemistry of freshwater and alkaline lacustrine sediments in the Green River Formation of the Washakie Basin, Wyoming, U.S.A. Organic geochemistry of freshwater and alkaline lacustrine sediments in the Green River Formation of the Washakie Basin, Wyoming, U.S.A.