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381.
Hock Hwee Heng Nikolas P. Nikolaidis 《Journal of the American Water Resources Association》1998,34(2):359-374
ABSTRACT: The Watershed Nutrient Transport and Transformation (NTT-Watershed) model is a physically based, energy-driven, multiple land use, distributed model that is capable of simulating water and nutrient transport in a watershed. The topographic features and subsurface properties of the watershed are refined into uniform, homogeneous square grids. The vertical discretization includes vegetation, overland flow, soil water redistribution and groundwater zones. The chemical submodel simulates the nitrogen dynamics in terrestrial and aquatic systems. Three chemical state variables are considered (NO3--, NH4+, and Org-N). The NTT-Watershed model was used to simulate the fate and transport of nitrogen in the Muddy Brook watershed in Connecticut. The model was shown to be capable of capturing the hydrologic and portions of the nitrogen dynamics in the watershed. Watershed planners could use this model in developing strategies of best management practices that could result in maximizing the reductions of nitrogen export from a watershed. 相似文献
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Breakthrough curves, on a semi-log scale, from tests in porous media with block-input of viruses, bacteria, protozoa and colloidal particles often exhibit a typical skewness: a rather slowly rising limb and a smooth transition of a declining limb to a very long tail. One-site kinetic models fail to fit the rising and declining limbs together with the tail satisfactorily. Inclusion of an equilibrium adsorption site does not seem to improve simulation results. This was encountered in the simulation of breakthrough curves from a recent field study on the removal of bacteriophages MS2 and PRD1 by passage through dune sand. In the present study, results of laboratory experiments for the study of this issue are presented. Breakthrough curves of salt and bacteriophages MS2, PRDI, and phiX174 in 1 D column experiments have been measured. One- and two-site kinetic models have been applied to fit and predict breakthrough curves from column experiments. The two-site model fitted all breakthrough curves very satisfactorily, accounting for the skewness of the rising limb as well as for the smooth transition of the declining limb to the tail of the breakthrough curve. The one-site model does not follow the curvature of the breakthrough tail, leading to an overestimation of the inactivation rate coefficient for attached viruses. Interaction with kinetic site 1 is characterized by relatively fast attachment and slow detachment, whereas attachment to and detachment from kinetic site 2 is fast. Inactivation of viruses and interaction with kinetic site 2 provide only a minor contribution to removal. Virus removal is mainly determined by the attachment to site 1. Bacteriophage phiX174 attached more than MS2 and PRD1, which can be explained by the greater electrostatic repulsion that MS2 and PRD1 experience compared to the less negatively charged phiX174. 相似文献
386.
Amanda Machin 《环境政策》2019,28(2):208-227
ABSTRACTOver the last three decades, ecological modernisation (EM) has emerged as a powerful political discourse, in which economic growth, environmental protection and energy security are mutually reinforcing. Here, the trajectory of EM in the European Union is traced, using a discourse analysis of the seven Environmental Action Programmes. The discourse articulated in these documents points towards an encroaching ‘double depoliticisation’. First, political decisions are discursively constructed as a matter of market rationality rather than a democratic process that engages with different political positions. Second, EM is reified as the only feasible solution, and alternative and contesting discourses are marginalised. Thus not only are political differences erased from the discourse, but the discourse is itself removed from political debate. 相似文献
387.
Brock TC Crum SJ Deneer JW Heimbach F Roijackers RM Sinkeldam JA 《Environmental pollution (Barking, Essex : 1987)》2004,130(3):411-426
Three different risk assessment procedures are described that aim to protect freshwater habitats from risks of the photosynthesis-inhibiting herbicides metribuzin and metamitron. These procedures are (1) the first-tier approach, based on standard toxicity tests and the application of an assessment factor, (2) the Species Sensitivity Distribution (SSD) approach, based on laboratory tests with a wider array of species and the application of a statistical model to calculate the HCx (the Hazardous Concentration for x% of the species), and (3) the model ecosystem approach, based on the evaluation of treatment-related effects in field enclosures. A comparison of the risk assessment procedures reveals that the first-tier approach is the most conservative for metamitron and metribuzin, and that HC5 values (and even HC10 values) based on acute EC50 values of algae and aquatic vascular plants may be used to derive maximum permissible concentrations for single applications. For both compounds these HC5 values were very similar to the ecological threshold concentrations in the enclosure studies. In contrast to model ecosystem experiments, however, HCx values based on lab toxicity tests do not provide information on the recovery potential of sensitive endpoints and on indirect effects, which may be important for regulatory decision-making. In the enclosure study, indirect effects of metribuzin on invertebrate populations were observed at an exposure concentration that was approximately 20 times lower than the corresponding HC5 value based on lab toxicity data for aquatic invertebrates. 相似文献
388.
氧化镁FGD脱硫过程的建模及其应用 总被引:8,自引:0,他引:8
氧化镁烟气脱硫是以氧化镁为脱硫反应剂的一种湿法烟气脱硫技术,目前国内外应用甚少,但开发前景广阔。以实验室小试为基础,从气液传质入手,利用双膜理论建立脱硫过程的数学模型,从而对中试脱硫效率进行预测并进行参数敏感性分析。结果表明,模型预测的脱硫效率与实际脱硫效率有很高的吻合度,其计算参数能反映出实际运行参数对脱硫效率的影响,对实际工况中操作条件的变更以及运行参数的调试有很高的指导意义。 相似文献
389.
In this study, organic pollutants in sandy soils are detected using a time domain relectrometry (TDR) probe system and eigendecomposition technique. As a demonstration, four types of organic fluids (motor oil, diesel oil, methanol and ethanol) were examined. Samples were prepared with different combinations of deionized water and organic fluid contents. For each experiment, reflected signals were captured by an oscilloscope, and their characteristics were identified using eigendecomposition technique. Autoregressive modeling and singular value decomposition methods were utilized for calculating the eigenvalues. The most significant eigenvalues were then identified based on their relative magnitude. Experimental results indicated that the presented system is sensitive to both water and pore fluid organic contents. For saturated conditions, signature curves were determined for identification of organic and/or water contents in soil pore fluids. 相似文献
390.
讨论了环境规划中区域社会-经济-环境模型建立的原则,提出了适合非定态城市发展过程中规划因子的预测方法,并给出了江苏靖江“十一五”期间环境规划中的具体应用。 相似文献