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This paper introduces a new direct method for measuring water and contaminant fluxes in porous media. The method uses a passive flux meter (PFM), which is essentially a self-contained permeable unit properly sized to fit tightly in a screened well or boring. The meter is designed to accommodate a mixed medium of hydrophobic and/or hydrophilic permeable sorbents, which retain dissolved organic/inorganic contaminants present in the groundwater flowing passively through the meter. The contaminant mass intercepted and retained on the sorbent is used to quantify cumulative contaminant mass flux. The sorptive matrix is also impregnated with known amounts of one or more water soluble 'resident tracers'. These tracers are displaced from the sorbent at rates proportional to the groundwater flux; hence, in the current meter design, the resident tracers are used to quantify cumulative groundwater flux. Theory is presented and quantitative tools are developed to interpret the water flux from tracers possessing linear and nonlinear elution profiles. The same theory is extended to derive functional relationships useful for quantifying cumulative contaminant mass flux. To validate theory and demonstrate the passive flux meter, results of multiple box-aquifer experiments are presented and discussed. From these experiments, it is seen that accurate water flux measurements are obtained when the tracer used in calculations resides in the meter at levels representing 20 to 70 percent of the initial condition. 2,4-Dimethyl-3-pentanol (DMP) is used as a surrogate groundwater contaminant in the box aquifer experiments. Cumulative DMP fluxes are measured within 5% of known fluxes. The accuracy of these estimates generally increases with the total volume of water intercepted. 相似文献
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Structural change and environmental impact: Empirical evidence on thirty-one countries in east and west 总被引:2,自引:0,他引:2
Martin Jänicke Harald Mönch Thomas Ranneberg Udo E. Simonis 《Environmental monitoring and assessment》1989,12(2):99-114
Although structural change in many industralized countries has increased since the early 1970s, the environmental policy aspects of this change have hardly been investigated. The more pronounced the positive environmental effects of structural change become, the more positive will be the structure-oriented options of environmental policy.Using a set of four indicators, in this study thirty-one Eastern and Western industrialized countries are being tested with regard to economic structure and environmentally significant structural change. The authors come to the conclusion that the strong correlation between economic performance and environmental pollution, unequivocal in 1970, had become much weaker by 1985. The de-linking of economic growth from material-intensive industrial production processes is particularly evident. In some cases automatic environmental benefits (environmental gratis effects) were generated in this way.However, the development profiles of the countries investigated differ greatly. There are countries, in particular Sweden, with absolute structural improvement in the ecological sense; countries like Japan and Norway with structural improvement relative to economic growth; and countries, including most Eastern and Southern European states, featuring no structural improvement or even environmentally negative structural change.The question is being left open to what extent the modernized economic structures are accompanied by modernized forms of environmental pollution. 相似文献
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