土壤與地下水污染題庫 1. Please explain the reason why the hydraulic gradient becomes steeper, forming a characteristic lowering of the water table or potentiometric surface (also called cone of depression) as the water approaches the borehole. (hints: using the Darcy’s law) 2. The movement of a contaminant through a natural system, such as an aquifer, is controlled by transport mechanisms. Please list and clarify these mechanisms. 3. Adsorption and desorption of organic molecules in soils in controlled by the chemical properties of the molecules and the surface properties of the particular soil. Please demonstrate the relevant properties in details. 4. A description of the chemical forms that an element takes in solution is termed its speciation. The speciation behavior of an element in soils profoundly affects its bioavailability. Environmental scientists argued that this concept should be applicable to the heavy metals. Please provide your own opinions for the statement. 5. What are the hierarchies of pollution prevention? Explain each of them. 6. What is ISO 14000? Please give benefits and pitfalls for ISO 14000. 7. What is the major agreement of Kyoto Protocol? The objective of the Kyoto Protocol will be defeated if what event occurs? 8. To achieve project objectives in a cost-effective manner, a clear strategy for mapping the contaminant zones must be established prior to commencement of field or laboratory work. Please provide a detail strategy for hydrogeologic site investigations. 9. What is NAPL? NAPLs have a tremendous impact on the remediation of contaminated aquifers, because it is very difficult or impossible to remove all of the residual NAPL blobs once they are trapped in individual pores. Please give a detail explanation for the above mentioned statement. 10. Please give a sketch of the effect of falling and rising water table on the distribution of mobile and residual phases on an LNAPL. 11. Unless the DNAPL observation well is screened directly within a DNAPL pool or lens and is constructed correctly, the apparent DNAPL thickness can give erroneous indications of the quantity of DNAPL in the formation. Please explain why? 12. Give some containment methods for source control to eliminate the potential spread of environmental contaminants. 13. Please give some examples for the abiotic transformations of heavy metals, such as Cr, As, and Hg, in the nevironment. 14. What is dose-response curve used for? If only single values from the dose-response curves are available, it must be kept in mind that those values will not provide any information about the shape of the curve. Please justify this statement. 15. Acute toxicity, which is often generated in tests because of the savings in time and expense, may not accurately reflect chronic toxicity dose-response relationships. Please give an example with detail explanations for above mentioned statement. 16. Given the following parameters for an aquifer, which received pollutants from adjacent industrial area. Porosity of 0.15 and water conductivity of 5 m/day. How long will the pollutant affect the water supply from a well 5000 m away from the discharge point? 17. Any of the “four” major characteristics will make a waste hazardous. Please specify each of them. 18. Site soil conditions frequently limit the selection of a treatment process. In addition, a treatment technology may be eliminated based upon the soil classification (e.g., particle-size distribution) or other soil characteristics (e.g., soil moisture, pH, variability, bulk density, particle density, permeability, Eh). Please give a throughout discussion of the influences of soil properties on the selection of a remediation strategy. 19. Of which heavy metals commonly found in contaminated sites in Taiwan do the plants fail to play the role of a biological alarm that would warn of toxicity? Will the inert response of plant to the metals, which you propose, affect the selection of treatment process? Explain why your answers are? 20. It is usual that a site that includes an unconfined aquifer separated from an underlying confined aquifer by a confining layer. Please sketch a procedure for installation of a monitoring well into the underlying confined aquifer without introducing contamination from above. 21. Define the terms point source and nopoint source and give some examples of each. Explain why nonpoint sources are often more difficult to control than point sources. 22. (A) Define the terms: degradable pollutants, non-degradable pollutants and persistent pollutants and give some examples of each. 23. Describe primary, secondary and tertiary wastewater treatments. What happens at each stage in the treatments and what pollutants are removed ? 24. Define the terms: natural eutrophication and anthropogenic eutrophication and explain the differences between them. Which inorganic nutrients are the main causes of anthropogenic eutrophication? Describe the major pathways for their transports from their sources to surface water? List some strategies for eliminating these nutrients from water. 25. Define the term natural succession. Describe how inorganic nutrients can accelerate natural succession in a lake. 26. Why chlorine gas is used to treat human sewage and drinking water? What dangers and problems does its use pose? Suggest two alternative substances that can be uses without causing these problems. 27. List at least three strategies for removing heavy metals from soils and describe the physical and chemical bases behind them. 28. Describe where phosphorus is removed from sewage water in an activated sludge wastewater treatment plant and give a balanced chemical reaction for lead removal in the tertiary stage. 29. Why do chlorinated hydrocarbons persist in the environment? Why do they posses threat to human health even though they are found in low concentration in water? 30. Give an example of the methods or techniques that are currently available for eliminating chlorinated hydrocarbons from soils and describe its physical, chemical or biological mechanisms. 31. Provide a conceptual figure to demonstrate the sequence of steps required to move sorbate molecules between soil solution and all the sorptive sites in a typical soil aggregate. 32. Give five reasons why it is important to know to what extent a given chemical is present in the sorbed form in a natural system. 33. What are the most important natural sorbents and sorption mechanisms for (a) apolar compound, (b) polar compounds, and (c) ionized compounds? 34. Why is soil organic matter (SOM) such an important sorbent for all organic compounds? What are the most important properties of SOM with respect to the sorption of organic compounds? 35. Provide the definition in words for (a) bioconcentration factor, (b) biomagnification factor, (c) bioaccumulation factor. 36. For what kind of organic compounds and in which environmentally relevant cases is adsorption of organic chemicals to inorganic surfaces in water important? Give five examples. 37. Three polychlorinated ethanes (1,1,2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane and pentachloroethane) are introduced into a lake by an accident. Calculate the half-life for chemical transformation of each of the three compounds in the lake (T=25 °C, pH=8.5). For each compound indicate the pH at which the neutral and base-catalyzed reactions would be equally important. What is (are) the transformation product(s) for these compounds? Compound Neutral reaction kN at 25 °C Base-catalyzed reaction kB (s-1) at 25 °C Cl2HC-CHCl2 Cl3C-CClH2 Cl3C-CHCl2 1.6x10-11 4.3x10-10 8.2x10-10 2.0x108 3.6x10-4 2.2x101 References: Environmental Science and Technology 22:658; 23:965. 38. Tetrachloroethylene (PCE) is a common organic solvent that may contaminate groundwater if leached through soil from a disposal site. Given its water solubility of about 5 mmol/L, estimate the distribution coefficient for PCE in a soil containing 20 g humus per kilogram. Is PCE immobilized well by the soil? log K OM 2.188 0.729 log S W ater K d K OM f OM Kd: the distribution coefficient of contaminants between soil and water KOM: the distribution coefficient of contaminants between organic matter and water. FOM: the organic matter fraction of soil. 39. Explain why sulfur cycle in sediments is related to the transformation and movement of some heavy metals in water. 40. Explain why in groundwater the transfer and transformation of arsenics is related to the transformation of Fe(II)/Fe(III) species.