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241.
The study analyzes the performance of an innovative cap-and-trade program designed to make cost-effective reductions of an ozone precursor in Chicago and finds that decentralized market incentives were undermined by the continuance of centralized traditional emission point or command-and-control regulation. The study makes two contributions for urban areas considering this regulatory measure: it shows that using two regulatory measures to achieve one emissions reduction goal can undercut cost-effective emissions trading, and it provides a redesign of the market system that coordinates both regulatory measures for cost-effective control and avoidance of trading problems, such as hot spots and inter-temporal spikes.  相似文献   
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The weathering of coal combustion products (CCPs) in a lotic environment was assessed following the Tennessee Valley Authority (Kingston, TN) fly ash release of 2008 into surrounding rivers. Sampled materials included stockpiled ash and sediment collected from 180 to 880 days following the release. Total recoverable concentrations of heavy metals and metalloids in sediment were measured, and percent ash was estimated visually or quantified by particle counts. Arsenic and selenium in sediment were positively correlated with percent ash. For samples collected 180 days after the release, total concentrations of trace elements downstream of the release were greater than reference levels but less than concentrations measured in stockpiled ash. Total concentrations of trace elements remained elevated in ash-laden sediment after almost 2.5 years. A sequential extraction procedure (SEP) was used to speciate selected fractions of arsenic, copper, lead, nickel, and selenium in decreasing order of bioavailability. Concentrations of trace elements in sequentially extracted fractions were one to two orders of magnitude lower than total recoverable trace elements. The bulk of sequentially extractable trace elements was associated with iron-manganese oxides, the least bioavailable fraction of those measured. By 780 days, trace element concentrations in the SEP fractions approached reference concentrations in the more bioavailable water soluble, ion exchangeable, and carbonate-bound fractions. For each trace element, the percentage composition of the bioavailable fractions relative to the total concentration was calculated. These SEP indices were summed and shown to significantly decrease over time. These results document the natural attenuation of leachable trace elements in CCPs in river sediment as a result of the loss of bioavailable trace elements over time.  相似文献   
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‘Live as domestic a life as possible. Have your child with you all the time. Lie down an hour after each meal. Have but two hours intellectual life a day. And never touch pen, brush or pencil as long as you live’. Dr S. Weir Mitchell, 1855 When Dr Mitchell, purportedly the greatest North American nerve specialist of his time, gave the above advice to his patient Charlotte Perkins Gilman, he almost certainly believed he was helping her get over a severe nervous condition. Fortunately, she did not take his advice. Instead she devoted herself to the study of economics and regained her health. The perspectives offered to working women by many a modern day Dr Mitchell appear to have changed somewhat in subtlety, but little in kind. For example, the August 18, 1986 cover of Fortune magazine featured a beaming mother and cherubic child illustrating the lead article, entitled ‘Why women are bailing out’. The article goes on to tell why four of the ‘best’ women MBAs had quit the workforce. One stated ‘I had to hire and fire people … I just don't want the hassle’ (of corporate life). Another having passed up a promotion at a Houston bank, ‘quit to have her first child’ and after her second had no plans to go back to work. A third complained: ‘I just couldn't do it. I watched other women sliding as they tried to juggle both career and family, making themselves crazy in the process’. And the fourth left a big accounting firm because the ‘hours were bad, and is now happier as a “part time teacher”’. While the Fortune article mentioned several reasons for women's leaving the corporate world ranging from competing family demands to discrimination, the underlying messages were clearly that mothers have to choose between children and career and that the business world is too cold, uncaring and tough for women, in a word no place for a lady. A chorus of such articles have appeared in the popular media warning against the dangers of career commitment for women, which are said to include everything from burnout, infertility, alcoholism, heart attacks to terminal spinsterhood (Faludi, 1991). More serious treatments emanating from academia have often reached similar conclusions. These dire pronouncements are especially influential to young women contemplating a professional or managerial career, but indeed those already in such careers may also wonder if they have made a bad choice. To answer such questions, this paper will explore some aspects of the relationship between career and emotional health and well-being for a group of highly successful career women.  相似文献   
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Ambio - The peregrine falcon (Falco peregrinus) and the gyrfalcon (Falco rusticolus) are top avian predators of Arctic ecosystems. Although existing monitoring efforts are well established for both...  相似文献   
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To investigate the coupled effects of solution chemistry and hydrodynamics on the mobility of quantum dot (QD) nanoparticles in the vadose zone, laboratory scale transport experiments involving single and/or sequential infiltrations of QDs in unsaturated and saturated porous media, and computations of total interaction and capillary potential energies were performed. As ionic strength increased, QD retention in the unsaturated porous media increased; however, this retention was significantly suppressed in the presence of a non-ionic surfactant in the infiltration suspensions as indicated by surfactant enhanced transport of QDs. In the vadose zone, the non-ionic surfactant limited the formation of QD aggregates, enhanced QD mobility and transport, and lowered the solution surface tension, which resulted in a decrease in capillary forces that not only led to a reduction in the removal of QDs, but also impacted the vadose zone flow processes. When chemical transport conditions were favorable (ionic strength of 5 × 10(-4)M and 5 × 10(-3)M, or ionic strengths of 5 × 10(-2)M and 0.5M with surfactant), the dominating phenomena controlling the mobility and transport of QDs in the vadose zone were meso-scale processes, where infiltration by preferential flow results in the rapid transport of QDs. When chemical transport conditions were unfavorable (ionic strength of 5 × 10(-2)M and 0.5M) the dominating phenomena controlling the mobility and transport of QDs in the vadose zone were pore-scale processes governed by gas-water interfaces (GWI) that impact the mobility of QDs. The addition of surfactant enhanced the transport of QDs both in favorable and unfavorable chemical transport conditions. The mobility and retention of QDs was controlled by interaction and capillary forces, with the latter being the most influential. GWI were found to be the dominant mechanism and site for QD removal compared with solid-water interfaces (SWI) and pore straining. Additionally, ripening phenomena were demonstrated to enhance QDs removal or retention in porous media and to be attenuated by the presence of surfactant.  相似文献   
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Forest cover in the upper Wabash River basin in Indiana was fragmented due to agricultural conversion beginning more than 175 years ago. Currently, urban expansion is an important driver of land-use change in the basin. A land transformation model was applied to the basin to forecast land use from 2000 to 2020. We assessed the effect of this projected land-use change scenario on five forest rodent species at three scales: using occupancy models at the patch level, proportional occupancy models at the landscape level, and ecologically scaled landscape indices to assess the change in connectivity at the watershed level. At the patch and landscape scales, occupancy models had low predictability but suggest that gray squirrels are most susceptible to land-use change. At the watershed scale, declines in connectivity did not correspond with the decline of forest. This study highlights the importance of map resolution and consideration of matrix elements in constructing forecast models. Unforeseen drivers of land use, such as changing economic incentives, may also have important ramifications.  相似文献   
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The United States funds a number of national monitoring programs to measure the status and trends of ecological and natural resources. Each of these programs has a unique focus; the scientific objectives are different as are the sample designs. However, individuals and committees, all well aware of the cost of ecological monitoring, have called for more effective monitoring programs. The objective of this paper is to summarize existing programs' statistical designs and discuss potential alternatives for improvement in national monitoring. Can we improve the current situation by providing an overall framework for the design or analysis of data from these disparate surveys? First, the paper summarizes the objectives of these surveys, compares and contrasts their survey designs as currently implemented, and determines what variables they collect. Through this process we identify commonalities and issues that impact our ability to combine information across one or more of the surveys. Three potential alternatives are presented, leading to comprehensive monitoring in the United States.  相似文献   
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