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381.
The species studied individually responded to different forms of mineral fertilizers introduced into the soil. Some species positively responded to the application of one nutrient (Easter-bell starwort, millet grass, and bilberry) or several nutrients (wood sorrel and hairy wood rush), whereas other species responded negatively. 相似文献
382.
The exchange of NO, NO2 and O3 at the soil surface wasmeasured with automatic dynamic chambers in a spruce forest and in abeech forest during periods of several months.NO was emitted from the soil at a rate of02013;8 ng N m-2 s-1(spruce) and 02013;15 ng Nm-2 s-1(beech), but there was no simple relationship between the flux andeither soil temperature or soil moisture. NO2 and O3 weredeposited at the soil surface. Deposition velocities forNO2were on average 0.3 mm s-1 (spruce) and 0.1 mms-1(beech), and the deposition velocities of O3 were on average 1.6 mm s-1 (spruce) and 1.4 mm s-1 (beech). The depositionvelocity of O3 is fairly constant whereas the deposition velocityof NO2 varies greatly, but the reasons remain to be investigated. 相似文献
383.
Udo E. Simonis 《The Environmentalist》2001,21(2):103-107
In the past, most of the attempts to improve the situation of the developing countries have focused on economic policy, on the conditions of international trade, on aid and direct investment. A debate on a New International Economic Order (NIEO) was launched in the 1970s (c.f. Tinbergen, 1976)—and largely failed (c.f. Simonis, 1989). This paper shows that environmental policy could be a more effective lever for improving the lot of the developing countries; the near future may see the evolution of a new international environmental order which is likely to better link environmental protection and economic development. 相似文献
384.
Robert G. McLaren Peter A. Forsyth Edward A. Sudicky Joel E. VanderKwaak Franklin W. Schwartz John H. Kessler 《Journal of contaminant hydrology》2000,43(3-4)
Recent discovery of bomb-related 36Cl at depth in fractured tuff in the unsaturated zone at the Yucca Mountain candidate high-level waste (HLW) repository site has called into question the usual modeling assumptions based on the equivalent continuum model (ECM). A dual continuum model (DCM) for simulating transient flow and transport at Yucca Mountain is developed. In order to ensure properly converged flow solutions, which are used in the transport simulation, a new flow solution convergence criteria is derived. An extensive series of simulation studies is presented which indicates that rapid movement of solute through the fractures will not occur unless there are intense episodic infiltration events. Movement of solute in the environs of the repository is enhanced if the properties of the tuff layer at the repository horizon are modified from current best-estimate values. Due to a large advective2013;dispersive coupling between the matrix and fractures, the matrix acts as a major buffer which inhibits rapid transport along the fractures. Consequently, fast movement of solutes through the fractures to the repository depth can only be explained if the matrix2013;fracture coupling term is significantly reduced from a value that would be calculated on the basis of data currently available. 相似文献
385.
Ashok Chilakapati Steve Yabusaki James Szecsody Warren MacEvoy 《Journal of contaminant hydrology》2000,43(3-4)
A research tool for modeling the reactive flow and transport of groundwater contaminants in multiple dimensions is presented. Arbitrarily complex coupled kinetic2013;equilibrium heterogeneous reaction networks, automatic code generation, transfer-function based solutions, parameter estimation, high-resolution methods for advection, and robust solvers for the mixed kinetic2013;equilibrium chemistry are some of the features of reactive flow and transport (RAFT) that make it a versatile research tool in the modeling of a wide variety of laboratory and field experiments. The treatment of reactions is quite general so that RAFT can be used to model biological, adsorption/desorption, complexation, and mineral dissolution/precipitation reactions among others. The integrated framework involving automated code generation and parameter estimation allows for the development, characterization, and evaluation of mechanistic process models. The model is described and used to solve a problem in competitive adsorption that illustrates some of these features. The model is also used to study the development of an in situ Fe(II)-zone by encouraging the growth of an iron-reducing bacterium with lactate as the electron donor. Such redox barriers are effective in sequestering groundwater contaminants such as chromate and TCE. 相似文献
386.
H. -W. Jacobi R. Weller A. E. Jones P. S. Anderson O. Schrems 《Atmospheric environment (Oxford, England : 1994)》2000,34(29-30)
Because investigations of PAN at higher southern latitudes are very scarce, we measured surface PAN concentrations for the first time in Antarctica. During the Photochemical Experiment at Neumayer (PEAN'99) campaign mean surface PAN mixing ratios of 13±7 pptv and maximum values of 48 pptv were found. When these PAN mixing ratios were compared to the sum of NOx and inorganic nitrate they were found to be equal or higher. Low ambient air temperatures and low PAN concentrations caused a slow homogeneous PAN decomposition rate of approximately 5×10−2 pptv h−1. These slow decay rates were not sufficient to firmly establish the simultaneously observed NOx concentrations. In addition, low concentration ratios of [HNO3]/[NOx] imply that the photochemical production of NOx within the snow pack can influence surface NOx mixing ratios in Antarctica. Alternate measurements of PAN mixing ratios at two different heights above the snow surface were performed to derive fluxes between the lower troposphere and the underlying snow pack using calculated friction velocities. Most of the concentration differences were below the precision of the measurements. Therefore, only an upper limit for the PAN flux of ±1×1013 molecules m−2 s−1 without a predominant direction can be estimated. However, PAN fluxes below this limit can still influence both the transfer of nitrogen compounds between atmosphere and ice, and the PAN budget in higher southern latitudes. 相似文献