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71.
The objective of this study was to reassess 99Tc transit times and transfer factors, from Sellafield to northern Norway, and to determine the extent of 99Tc migration to the Barents Sea. Filtered seawater samples were collected on a monthly basis from Hilles?y, northern Norway, and in February 1999 from the Barents Sea. Results showed an increase in levels of 99Tc at Hilles?y where activity concentrations have increased from a baseline of 0.2-0.4Bq m(-3) to a maximum of 1.6 Bq m(-3). A transit time of 42 months and a transfer factor of 6Bq m(-3) per PBq a(-1) have been derived, using cross-correlation analysis. The current study predicts that future levels are unlikely to increase dramatically over the levels observed in 1998. Levels of 99Tc in the Barents Sea ranged from 0.2 Bq m(-3) to 1.1 Bq m(-3) showing the influence of new 99Tc inputs by early 1999.  相似文献   
72.
The environmental fate and transport of chlorinated volatile organic compounds (VOCs) is controlled by the physical and chemical properties of the compound and the nature of the subsurface media through which the compound is migrating. Several processes (advection, dispersion, diffusion, biodegradation, and abiotic degradation, to name a few) result in a reduction in concentration and/or mass of contaminants in groundwater. Of these processes, biodegradation is often considered the dominant destructive attenuation mechanism for chlorinated VOCs. However, chlorinated VOCs can also degrade through abiotic processes and, in some cases, may be the primary or only destructive process occurring. © 2007 Wiley Periodicals, Inc.  相似文献   
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ABSTRACT: For many years, Federal water resources projects have been subjected to benefit-cost analysis to establish their economic feasibility. Several years ago social well-being was added as a consideration. This paper discusses the state-of-the-art in analyzing and evaluating aspects of social well-being. It stresses current short-falls and advocates a direction for further efforts.  相似文献   
75.
Global Reporting Initiative (GRI) is the best-known framework for voluntary reporting of environmental and social performance by business worldwide. Using extensive empirical data, including interviews and documentary analysis, we examine GRI's organizational field and conclude that since its modest beginnings in 1999 GRI has been by several measures a successful institutionalization project. But the institutional logic of this new entity, as an instrument for corporate sustainability management, leaves out one of the central elements of the initial vision for GRI: as a mobilizing agent for many societal actors. This emergent logic reflects GRI's dominant constituency – large global companies and financial institutions and international business management consultancies – and not the less active civil society organizations and organized labor. We attribute these developments to factors such as building GRI within the existing institutional structures; the highly inclusive multistakeholder process; and the underdeveloped base of information users. From the institutional theory perspective, this case shows how the process of institutionalization is deeply affected by initial strategies of the founders, and how it reproduces existing power relations. From the governance perspective, this case leads us to question the power of commodified information to mobilize civil society and to strengthen governance based on partnerships.  相似文献   
76.
The asymptotic behavior of a linear compartment model for the environmental movement of radionuclides is investigated. Here, the expression asymptotic behavior is used to designate the behavior of q(t) as t → ∞, where q is the solution of a vector differential equation of the form dq/dt = h + Kq. The asymptotic behavior of such equations is described. For the model and conditions under consideration, each element of q converges monotonically to a steady-state value. A hydrologic system is defined and used to illustrate this behavior. An approach to sensitivity analysis employing Latin hypercube sampling, rank transformations and stepwise regression is presented and then applied to this system. A total of 20 independent variables is introduced and the following dependent variables are investigated for the various components of the system: amount of radionuclide present at steady state. concentration of radionuclide at steady state, and time required to reach 90% of steady state. Finally, an application of asymptotic behavior in the analysis of a hypothetical site for the geologic isolation of high-level radioactive waste is described and a brief discussion of differential sensitivity analysis is given.  相似文献   
77.
There is general consensus that carbon (C) sequestration projects in forests are a relatively low cost option for mitigating climate change, but most studies on the subject have assumed that transaction costs are negligible. The objectives of the study were to examine transaction costs for forest C sequestration projects and to determine the significance of the costs based on economic analyses. Here we examine four case studies of active C sequestration projects being implemented in tropical countries and developed for the C market. The results from the case studies were then used with a dynamic forest and land use economic model to investigate how transaction costs affect the efficiency and cost of forest C projects globally. In the case studies transaction costs ranged from 0.38 to 27 million US dollars ($0.09 to $7.71/t CO2) or 0.3 to 270 % of anticipated income depending principally on the price of C and project size. The three largest cost categories were insurance (under the voluntary market; 41–89 % of total costs), monitoring (3–42 %) and regulatory approval (8–50 %). The global analysis indicated that most existing estimates of marginal costs of C sequestration are underestimated by up to 30 % because transaction costs were not included.  相似文献   
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79.
Urban stream restoration continues to be used as an ecological management tool, despite uncertainty about the long‐term sustainability and resilience of restored systems. Evaluations of restoration success often focus on specific instream indicators, with limited attention to the wider basin or parallel hydrologic and geomorphic process. A comprehensive understanding of urban stream restoration progress is particularly important for comparisons with nonurban sites as urban streams can provide substantial secondary benefits to urban residents. Here, we utilize a wide range of indicators to retrospectively examine the restoration of Nine Mile Run, a multi‐million dollar stream restoration project in eastern Pittsburgh (Pennsylvania, USA). Examination of available continuous hydrological data illustrates the high cost of failures to incorporate the data into planning and adaptive management. For example, persistent extreme flows drive geomorphic degradation threatening to reverse hydrologic connections created by the restoration and impact the improved instream biotic communities. In addition, human activities associated with restoration efforts suggest a positive feedback as the stream restoration has focused effort on the basin beyond the reach. Ultimately, urban stream restoration remains a potentially useful management tool, but continued improvements in post‐project assessment should include examination of a wider range of indicators.  相似文献   
80.
Few studies exist on how chloride from chloride‐based deicers is transported in infiltration‐based stormwater control measures. In 2009, the U.S. Environmental Protection Agency (USEPA) constructed a 0.4 ha parking lot in Edison, New Jersey, that was surfaced with permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). Each surface type has four equally sized, lined sections that direct all infiltrate to separate 5.7 m3 collection tanks. The USEPA acute criterion for aquatic life (860 mg/l) was exceeded in events immediately following a snow event. Concentrations of the infiltrate exceeded the detection limit (5 mg/l) year round but did not exceed the USEPA chronic toxicity (230 mg/l) after April. The chloride concentration decreased with cumulative rainfall since previous snow event, and a power regression described this relationship. In the power regression, the coefficient (b) described the initial concentration following a snow event, and the exponent (m) described the rate in which chloride was flushed through the system with infiltrating water. PC had the largest coefficient (5,664) and largest absolute exponent (?0.92), followed closely by PICP (= 4,943 and = ?0.87), and distantly by PA (= 2,907 and = ?0.67). The differences in release rate were proportional to the measured surface infiltration rates of 4,000; 2,400; and 200 cm/h for PC, PICP, and PA, respectively. These results will assist those who manage or regulate stormwater where receiving waters are chloride impaired.  相似文献   
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