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881.
Frederick M. Fisher Kenneth L. Dickson John H. Rodgers Keith Anderson John Slocomb 《Journal of the American Water Resources Association》1988,24(5):1017-1026
ABSTRACT: A method to partition the variation in concentrations of water chemistry parameters in a river is described. The approach consists of fitting a family of curves for each chemical parameter. Each curve indicates the response of the parameter to river flow for a particular time period or location. An analysis of covariance is then used to identify statistically significant differences between curves. Such differences result largely from two factors: (1) the discharge of effluents and (2) river flow-concentration relationships. The deviations from the fitted curves indicate month-to-month variations unrelated to river flow that are controlled by factors such as temperature-related seasonal patterns. Underlying statistical assumptions are discussed with respect to water chemistry data. The technique is applied to a data set consisting of monthly samples of 22 water chemistry parameters from the Sulphur River of Texas and Arkansas. Several patterns of response to river flow and to two effluent discharges were revealed. 相似文献
882.
Davar Khalili Lucien Duckstein Martin M. Fogel 《Journal of the American Water Resources Association》1988,24(5):1035-1040
ABSTRACT: Resource utilization as practiced by humans is identified as the main cause of the degradation of rangeland watersheds, a process referred to as desertification. This paper introduces a multi-objective decision making methodology for the selection of a plan which if implemented should limit the desertification process. The evaluation objectives are measured by quantitative and qualitative criteria. The quantitative criteria provide the performance level for production and sediment yield, while the qualitative criteria give such information as public acceptance of a particular alternative or worth of an appropriate wildlife habitat. A system model is applied to describe the dynamics of a range site in response to climatic and human inputs. As such it provides the information required by the quantitative criteria as well as a range condition index that identifies the productivity of a given range site. A multiobjective selection procedure is presented that will lead to the appropriate technique from an available set, in this case ESAP, Environmental Sensitivity Analysis Package. Four individuals with diverse backgrounds in natural resource management participated as decision makers and decided on their preferred alternatives. Finally, ranked alternatives in agreement with all of the decision makers were obtained. 相似文献
883.
David J. Wilson 《Environmental monitoring and assessment》1997,48(1):73-100
Diffusion of VOC from cylindrical vadose zone domains contaminatedwith distributed nonaqueous phase liquid is examined in the steadystate approximation. The effects of first-order biodegradation and ofan extended underlying pool of LNAPL floating on the water table belowthe cylindrical domain are explored by means of an orthogonal functionsapproach. The distribution of VOC in the vadose zone above a floatingcircular LNAPL pool of finite size is explored by a numerical method.The results provide information useful in estimating the spacing anddepth at which soil gas samples should be taken in order to detect thepresence of such source areas. Comparison of model results with soilgas VOC measurements at various depths also provides insight into theextent to which natural biodegradation of the VOCs is taking place. 相似文献
884.
Monitoring and dispersion modelling of emissions from the fluidised bed combustion of poultry litter
Henihan AM Kelleher BP Leahy MJ Cummins E Leahy JJ 《Environmental monitoring and assessment》2003,85(3):239-255
Gaseous emissions from the fluidised bed combustion of chickenlitter were monitored and recorded. Emission data was used tocreate a dispersion model for a proposed site on a poultry farmin Limerick, Ireland. Variables within the combustion unit notonly influenced combustion but also emission levels ofpollutants such as SO2 and NOx. CO emissions decreased withuse of the correct ratio between fluidising and secondary air,the staging of secondary air and the degree of turbulence withwhich the secondary air is introduced. Dispersion modelling ofactual combustion at a proposed poultry unit predicted thatground level concentrations for the set of emissions data wouldbe below the limits and guidelines set by air quality standards.This was true for both and line source. Line sourceconcentration levels were less than those for point source. 相似文献
885.
Operational and Design Considerations of a Trickling Filter for Ammonia Removal from Potable Water 总被引:1,自引:0,他引:1
We studied the steady-state behavior of a mathematical model of a nitrifying trickling filter. In particular, we studied the effect of the operating conditions of the filter on the complete and safe nitrification. We presented the results with the help of the operating diagram of the system and we determined the range of operating conditions resulting in optimal operation. We also computed biofilm thickness along the filter depth and concentration profiles inside the biofilm, and compared them with experimental results found in the literature. The comparison shows very good qualitative agreement between model predictions and experimental data. 相似文献
886.
887.
Hashem A. Faidi Luis A. Garcia Maurice M. Albertson 《Environmental Modeling and Assessment》2002,7(3):191-206
A model for simulation of solute transport in a dynamic stream–aquifer system is developed by integrating four existing sub-models. Interface packages are created to link the sub-models. The developed model is successfully used to simulate chloride transport in the stream–aquifer system of the Arkansas River and the Equus Beds Aquifer in Kansas and demonstrates that chloride concentration in the aquifer decreases in the vicinity of the simulated channel over time. 相似文献
888.
Monitoring the results of Canada/U.S.A acid rain control programs: some lake responses 总被引:1,自引:0,他引:1
Jeffries DS Brydges TG Dillon PJ Keller W 《Environmental monitoring and assessment》2003,88(1-3):3-19
Aquatic acidification by deposition of airborne pollutants emerged as an environmental issue in southeastern Canada during the 1970s. Drawing information from the extensive research and monitoring programs, a sequence of issue assessments demonstrated the necessity of reducing the anthropogenic emissions of acidifying pollutants, particularly sulphur dioxide (SO2). The 1991 Canada-U.S. Air Quality Agreement (AQA) was negotiated to reduce North American SO2 emissions by 40% relative to 1980 levels by 2010, and at present, both countries have reduced emissions beyond their AQA commitment. In response to reduced SO2 emissions, atmospheric deposition of sulphate (SO4
2–) and SO4
2– concentrations in many lakes have declined, particularly in south-central Ontario and southern Québec. Sulphate deposition still exceeds aquatic critical loads throughout southeastern Canada however. Increasing pH or alkalinity (commonly deemed recovery) has been observed in only some lakes. Several biogeochemical factors have intervened to modify the lake chemistry response to reduced SO4
2– input, notably release of stored SO4
2– from wetlands following periods of drought and reduction in the export of base cations from terrestrial soils. Three examples from Ontario are presented to illustrate these responses. Significant increases in pH and alkalinity have been observed in many lakes in the Sudbury area of Ontario due to the large reductions in local SO2 emissions; early-stage biological recovery is evident in these lakes. An integrated assessment model predicts that AQA emission reductions will not be sufficient to promote widespread chemical or biological recovery of Canadian lakes. Monitoring and modeling are mutually supporting assessment activities and both must continue. 相似文献
889.
A coupled three-dimensional hydrodynamic–ecological model was used for the assessment of water quality in Narva Bay during one biologically active season. Narva Bay is located in the south-eastern Gulf of Finland. Narva River with a catchment’s area covering part of Russia and Estonia discharges water and nutrients to Narva Bay. The ecological model includes phytoplankton carbon, nitrogen and phosphorus, chlorophyll a, zooplankton, detritus carbon, nitrogen and phosphorus, inorganic nitrogen, inorganic phosphorus and dissolved oxygen as state variables. Both the hydrodynamic and ecosystem models were validated using a limited number of measurements. The hydrodynamic model validation included comparison of time series of currents and temperature and salinity profiles. The ecological model results were compared with the monitoring data of phytoplankton biomass, total nitrogen and phosphorus and dissolved oxygen. The comparison of hydrodynamic parameters, phytoplankton biomass, surface layer total phosphorus and dissolved oxygen and near-bottom layer total nitrogen was reasonable. Time series of spatially mean values and standard deviations of selected parameters were calculated for the whole Narva Bay. Combining model results and monitoring data, the characteristic concentrations of phytoplankton biomass, total nitrogen and phosphorus and near-bottom dissolved oxygen were estimated. Phytoplankton biomass and total phosphorus showed seasonal variations, of 0.6–1.1 and 0.022–0.032 mg/l, respectively, during spring bloom, 0.1–0.3 and 0.015–0.025 mg/l in summer and 0.2–0.6 and 0.017–0.035 mg/l during autumn bloom. Total nitrogen and near-bottom oxygen concentrations were rather steady, being 0.25–0.35 and 2–6 mg/l, respectively. The total nitrogen and phosphorus concentrations show that according to the classification of Estonian coastal waters, Narva Bay water belongs to a good water quality class. 相似文献
890.
The purpose of the present study was to evaluate the groundwater contamination due to the construction and operation of the
municipal landfill of Amari, Rethymno, Crete. The groundwater flow and leachate transport in the vadose and saturated zones
were studied and simulated, using three different models: the one-dimensional groundwater flow and contaminant transport model
for the vadose zone Pesticide Root Zone Model (PRZM-3), the Geographical Information System (GIS) Argus ONE and the three-dimensional
groundwater flow and contaminant transport model Princeton Transport Code (PTC). The simulation time was 30 and 20 years,
and the results obtained, according to the models and the existing hydrogeological conditions, were very encouraging and reassuring
about the groundwater quality of the broad region. 相似文献