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41.
There is a growing need to assess and monitor forest cover and its conservation status over global scales to determine human impact on ecosystems and to develop sustainability plans. Recent approaches to measure regional and global forest status and dynamics are based on remotely sensed estimates of tree cover. We argue that tree cover should not be used to assess the area of forest ecosystems because tree cover is an undefined subset of forest cover. For example, tree cover can indicate a positive trend even in the presence of deforestation, as in the case of plantations. We believe a global map of forest naturalness that accounts for the bio-ecological integrity of forest ecosystems, for example, intact forests, old-growth forest patches, rewilding forests (exploited forest landscapes undergoing long-term natural succession), and managed forests is needed for global forest assessment. 相似文献
42.
Riccardo Rossi Gianluca Iaccarino 《Atmospheric environment (Oxford, England : 1994)》2009,43(16):2518-2531
We present a numerical study of scalar transport released from a line source downstream of a square obstacle to investigate the capabilities and limitations of gradient-transport modeling in predicting atmospheric dispersion. The standard k–? and k–ω models and a Reynolds Stress Transport closure are employed and compared to predict the time-averaged turbulent flow field, while a standard gradient–diffusion model is initially adopted to relate the scalar flux to mean gradients of the concentration field. The analysis of two algebraic closures for turbulent scalar fluxes based on the generalized-gradient–diffusion hypothesis and its quadratic extension is also presented. In spite of the rather simple flow setup, where both the flow and the scalar fields can be assumed homogeneous in the spanwise direction, the analysis clarifies several critical issues concerning gradient-transport type models. We established the dominant role of predicted turbulent kinetic energy on scalar dispersion when a scalar diffusivity is employed, irrespectively of the Reynolds stress closure adopted for the averaged momentum equation. Moreover, the standard gradient–diffusion hypothesis failed to predict the streamwise component of the scalar flux, which is characterized by a counter-gradient-transport mechanism. Although the resulting contribution in the averaged scalar transport equation is small in the present flow configuration, this limitation can become severe for strongly inhomogeneous flows in the presence of point sources, where the spread of the scalar plume is essentially three-dimensional. The predictive capabilities of gradient-transport type modeling are found clearly improved using algebraic closures, which appear to represent a promising tool for predicting atmospheric dispersion in complex flows when unsteady transport mechanisms are not dominant. 相似文献
43.
Mosca S Torelli GN Guerriero E Tramontana G Pomponio S Rossetti G Rotatori M 《Journal of environmental monitoring : JEM》2010,12(5):1092-1099
The Stockholm Convention on Persistent Organic Pollutants (POPs) was signed in May 2001 by 127 countries. Currently, 12 substances are regulated by the convention, and the work on finding new candidate chemicals to the convention has started. Among these 12 substances, dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are the objects of this study. There are no European standard methods for the simultaneous determination of these microorganic compounds, together with polycyclic aromatic hydrocarbons (PAHs) in ambient air--they must be referred to three different methods developed by the U.S. Environmental Protection Agency (EPA). The quali-quantitative analysis of these microorganic pollutants is an important challenge due to the low concentrations at which they may be present. In this study, the development of a simplified, alternative, fast and affordable sampling method for the determination of PAHs, PCDDs, PCDFs and PCBs in ambient air was performed. The sampling time was extended from 24 h to 7 d in order to enrich the sample, to fall within the instrumental limits of detection and to reduce the number of samples to be processed and, therefore, errors that may arise. First of all, experiments with labelled standards were conducted in the research area of Montelibretti (rural station, which is sited about 20 km northeast of Rome), with the purpose of optimizing sampling efficiency. Finally, the method was applied to the analysis of these compounds in the air of a suburban area with small industrial plants in order to evaluate the feasibility of the proposed sampling method system, by comparing concentrations of native compounds acquired during simultaneous daily and weekly sampling. 相似文献
44.
Gianluca Grilli Isabella De Meo Giulia Garegnani Alessandro Paletto 《Journal of Environmental Planning and Management》2017,60(7):1276-1295
A multi-criteria analysis (MCA) was implemented to assess the best solutions for enhancing the production of renewable energy in the Alps. A set of criteria were selected based on the impacts of four renewable energy sources (forest biomass, hydropower, ground solar photovoltaic and wind power) on the three spheres of sustainability (environmental, social and economic). Three different scenarios are presented, each with a different set of weights for the criteria: the first scenario considers equally all three aspects of sustainability; the second scenario foresees an environmentally-oriented perspective, while the third scenario is more focused on the socio-economic aspects related to the development of renewable energy. Results show that forest biomass and hydropower seem to be the most viable solutions for enhancing the share of renewable energy in the Alps. Ground solar photovoltaic and wind power, on the other hand, seem to be less attractive alternatives due to their high impacts on land use. 相似文献
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46.
Arturs Purvins Heinz Wilkening Gianluca Fulli Evangelos Tzimas Gianni Celli Susanna Mocci Fabrizio Pilo Sergio Tedde 《Journal of Cleaner Production》2011,19(17-18):1909-1916
This article assesses the impact of extensive deployment of indigenous and external renewable energy sources on a local electricity system (Sardinia Island) and discusses the main challenges faced by the European power grids in integrating high shares of renewable-based generation technologies. It presents the 2030 scenarios for the Sardinian power system and the results of steady-state analyses in extreme (renewable) generation and consumption conditions. These results are eventually combined with the assessment of key technology development trends to explain how this can affect the development of a European supergrid. In general, the article stresses that rendering the bulk-power system capable of accommodating high renewable energy penetration not only requires reinforcing the electricity highways but also demands carefully planning the architecture of and the interface with regional power systems. 相似文献
47.
This paper describes an innovative process to increase superheated steam temperatures in waste-to-energy (WTE) plants. This solution is mainly characterised by a fluidised bed reactor in which hot flue gas is treated both chemically and mechanically. This approach, together with gas recirculation, increases the energy conversion efficiency, and raises the superheated steam temperature without decreasing the useful life of the superheater. This paper presents new experimental data obtained from the test facility installed at the Hera S.p.A. WTE plant in Forlì, Italy; discusses changes that can be implemented to increase the duration of experimental testing; offers suggestions for the design of an industrial solution. 相似文献
48.
We examined the role of social embeddedness in creating positive perceptions of organizational support among managerial and staff employees (n = 72) of a large manufacturing firm. We operationalized social embeddedness as the size, density, and quality of employees' networks of multiplex, reciprocated exchange relationships with colleagues. After controlling for support from supervisors and upper management, we found all three aspects of social embeddedness to be associated with perceived organizational support (POS). This research suggests that in addition to the top‐down influence of the organizational hierarchy, POS results from the organizational community within which employees are embedded through their social network in the workplace. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
49.
Martina Milanese Antonio Sarà Gianluca Sarà Jason H. Murray 《Chemistry and Ecology》2013,29(2):95-105
This commentary describes a gap in the qualitative and quantitative knowledge of the provision of benefits to humans from the intertidal ecosystems of the Mediterranean and offers a framework for quantification of the benefits provided by these systems. The identification of such benefits, understanding their spatial distribution and their subsequent quantification will be critical to the design of policy responses to future climate change, sea level rise and seawater acidification. A baseline understanding of the current state of ecosystem functions, as well as of the provision of related ecosystem services, is therefore needed. Further, researchers must strive to generate forecasts of the changes in these functions and services conditional on policy responses and the range of expectations for climate change. 相似文献
50.
International institutions, understood as sets of rules contained in international agreements, are aimed at orienting national
governments towards specific policy options. Nevertheless, they can determine a change in national policies and practices
only if states are willing and capable of incorporating international obligations into their national legislations and ensuring
their application and enforcement in areas that follow completely under national jurisdiction. The establishment of marine
protected areas promoted by international agreements as a tool for the protection of marine resources represents an interesting
case for revealing the complex interactions between international institutions and national actors. Particularly, the establishment
of these areas in Senegal shows the salience of domestic constellations of actors who may support or undercut national commitments
to international regimes: political elites, bureaucracies, the general public and target groups. By anchoring the empirical
analysis to an actor-centred institutionalist perspective, the article explains how dynamic constellations of actors can distort
the penetration of international objectives in the national policy framework. Different constellations of national actors
can indeed bend international institutions at different moments: during the formulation of a new law in line with international
obligations; in the definition of its implementation framework; and in the enforcement of national policies. 相似文献