摘要:

Prediction of the movement of contaminants in groundwater systems through the use of models has been given increased emphasis in recent years because of the growing trend toward subsurface disposal of wastes. Prediction is especially critical when nuclear wastes are involved. Contaminant transport models which include the effects of dispersion have been applied to several field situations. However, factors that limit the routine use of these models include the difficulty of determining the field coefficient of dispersion and numerical difficulties encountered when solving the dispersion equation. Regional size models which neglect the effects of dispersion have had limited success because of the scarcity and poor quality of field data. Another difficulty in the development of contaminant transport models is the current lack of knowledge regarding the quantification of chemical reaction terms. This review examines the formulation of contaminant transport models, application to field problems, difficulties involved in obtaining input data, and current status of modeling efforts.

ISSN:0007-8999    

DOI:10.1080/10643387909381669

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Results of computer simulation of methane migration around sanitary landfills are presented. Five computer codes, designed to treat a variety of landfill configurations and migration control schemes are described. Typical results for the migration codes are given in the form of printouts of methane mole fraction as a function of position and time. These results are used to generate design charts which allow planners to assess whether there is a potential methane migration hazard at a given site. If such potential exists, the appropriate codes can be run using additional site specific data. Migration control configurations treated include pumped and unpumped trenches and pipes as well as barriers. Also treated are hybrid systems involving pumped or unpumped trenches with barriers installed on the outside of the trench. A case history is presented wherein several migration design alternatives are compared for a particular site. The best configuration is then studied in more detail to optimize the design. Finally, the effects of system shut down are evaluated to determine the probable rate of readvance of methane.

ISSN:0007-8999    

DOI:10.1080/10643387909381670

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Freshwater wetlands can, in some circumstances, renovate added secondarily treated wastewater, thus providing an alternative to land or water disposal or expensive physical‐chemical treatment processes. This review summarizes North American studies in the contexts of ecosystem function and water quality changes, for both natural and artificial wetland ecosystems. All components of an ecosystem are involved in the alteration of the dissolved nutrient status and sediment content of the water. The results of recent studies are interpreted in terms of the principles of hydrology and nutrient cycling in wetlands. Initial uptake and alteration mechanisms involve sorption and microbial processes, such as denitrification. Peat soils provide a maximum condition for this rapid uptake. Detritus supports microbial populations and active periphyton, which coupled with other algae, represent a second temporary sink. The vascular plant community also represents nutrient storage which may be exploited by herbivores or detritivores. Decomposition subsequently releases some of the nutrients to recycle, while the remainder is stored as peat. The buffer performance of these ecosystems is interpreted in light of prevailing economic, political, and regulatory considerations.

ISSN:0007-8999    

DOI:10.1080/10643387909381671

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor