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1.
Challenges in quantifying biosphere-atmosphere exchange of nitrogen species   总被引:2,自引:0,他引:2  
Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas-aerosol interactions, organic nitrogen and N(2) fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N(2)O, NO and bi-directional NH(3) exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols.  相似文献   
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Plants of soybean (Glycine max L.) were grown with and without the ozone protectant EDU (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-n2 phenylurea) at a suburban site, a remote rural site and a rural roadside site around the city of Lahore, Pakistan. The development and yield of the plants was determined in two experiments--one immediately post-monsoon and one in the following spring (pre-monsoon). Concentrations of nitrogen dioxide and photochemical oxidants were measured at each site. The effect on yield of EDU at the suburban site (47 and 113% increase in seed weight per plant relative to the untreated plants in the post- and pre-monsoon experiments, respectively) was similar to the effects of filtration on yield on soybean in a parallel open-top chamber study at the same site (77% increase relative to plants subjected to unfiltered air for the pre-monsoon experiment). Effects of EDU on yield were greater at both rural sites than at the suburban site in both experiments, and greater in the spring experiment (182% at the remote rural site and 285% at the rural roadside site) than in the post-monsoon experiment (94% at the remote rural site and 170% at the rural roadside site); oxidant concentrations were also greater at the rural sites than at the suburban site, and greater in the spring experiment than the post-monsoon experiment. The results imply that ozone may be causing significant crop losses in rural areas around Lahore; however, the geographical extent of the problem, and the implications for peri-urban agriculture around other cities of south Asia are uncertain.  相似文献   
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Anuran populations are sensitive to changing environmental conditions and act as useful indicators. Presently, much information collected concerning frog populations comes from volunteers following the North American Amphibian Monitoring Protocol. Does weather variability allowed within protocol affect the abundance of calling frogs? For 10 years, Credit Valley Conservation (Ontario, Canada) has been collecting anuran data concerning nine frog species employing three frog monitoring runs. Records include frog abundance by protocol code and five weather variables. Antecedent precipitation and temperature were determined from the nearest weather station. Locations with large source populations of two Hylidae species were selected (spring peeper calling in April and gray tree frog in May). Spearman correlations suggested there were no significant relationships between calling abundance of Hylidae species and ambient wind speed or humidity. However, gray tree frogs were temperature sensitive and calling was significantly related to increased water and air temperatures as well as day time high temperatures over the previous 2 weeks. Both species of calling Hylidae were affected by the volume and timing of precipitation (though, in different ways). Gray tree frogs seem to prefer drier conditions (when temperatures are significantly warmer) while spring peepers prefer to call during, or closely following, precipitation. Monitors targeting gray tree frog should track local weather conditions and focus on evenings when it is (a) warmer than the minimum temperatures and (b) drier than suggested by the protocol. It is recommended that an additional monitoring run could be added to reduce detection variability of this species.  相似文献   
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Managing Watershed Externalities in India: Theory and Practice   总被引:2,自引:0,他引:2  
Watershed development is the focus of poverty alleviation programs in rural India. Watershed projects aim to solve problems of externalities, but they also create their own externalities, which cause uneven distribution of costs and benefits that undermine project objectives and harm the poor. Numerous approaches exist to internalize externalities, including awareness creation, moral suasion, investment subsidies, regulatory limits and fines, indirect benefits, mergers, and recent innovations like payment for environmental services and cap and trade. These can be judged on several criteria; the best approach would solve the problem cost effectively and help or at least not hurt poor people. Watershed projects in India were examined to identify the approaches taken to internalize watershed externalities. Investment subsidies and indirect employment benefits are the least effective approaches theoretically, but they are the most commonly applied, most likely because they are easy to administer and bring popular short term gains. Some theoretically favorable approaches that have been used elsewhere, such as payment for environmental services, may not work as well in India due to high transaction costs. However, one key innovation that easily could be applied in India is to make investment subsidies contingent on performance. Legal support and property rights reform would be needed for other favorable approaches.  相似文献   
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This paper is the report of a meetingthat gathered many of the UK's most senioranimal scientists with representatives of thefarming industry, consumer groups, animalwelfare groups, and environmentalists. Therewas strong consensus that the current economicstructure of agriculture cannot adequatelyaddress major issues of concern to society:farm incomes, food security and safety, theneeds of developing countries, animal welfare,and the environment. This economic structure isbased primarily on competition betweenproducers and between retailers, driving foodprices down, combined with externalization ofmany costs. These issues must be addressed by acombination of legislation, restructuring ofthe market, and use of public funds. Themeeting included workshops that made otherrecommendations for research and education. Themost urgent requirement is recognition thatchange is needed and development of a visionfor what that change must achieve.  相似文献   
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A methodology was developed to prioritize the suitability of sites for long-term monitoring of avian populations, including vulnerable species, both to enhance assessment of changes in ecological resources and to facilitate land-use planning at the regional scale. This paper argues that a successful monitoring program begins with a site prioritization procedure that integrates scores based on spatial controls with ecological and socio-economic indicators, particularly those dependent on community involvement. The evaluation strategy in this study combines 1) spatial controls such as land ownership and accessibility, with 2) biological and habitat indicators such as vulnerable species and habitat connectivity, and 3) community and agency variables such as volunteer commitment and agency priorities. In total, a set of ten indicators was identified. This strategy was applied to predominantly agricultural landscapes, which are experiencing increasing human pressures, in three sub-watersheds of the Credit River, Southern Ontario. Specifically, bird populations were recorded during the breeding seasons of 2000-2002 in nine land units or habitat types including marsh, deciduous forest, and grasslands as mapped by Credit Valley Conservation (CVC) following Ecological Land Classification (ELC) guidelines. CVC selected sites for long-term monitoring in 2002 and the relationships between the scored (or ranked) sites and the selected long-term monitoring sites are discussed.  相似文献   
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Natural bioluminescence (that not mechanically stimulated by human intervention) produced by organisms on the seafloor of the northeast Atlantic ocean between 970 and 4,800 m depth was examined using an image intensifying (ISIT) camera mounted on an autonomous lander system. In the absence of bait little or no luminescence was observed but with bait present there was a significant inverse relationship with depth, Log10 (1 + number of events h−1) = 1.7627–0.3235 depth (km) (r 2 = 0.8158, P < 0.001) indicating an average of 2.6 events h−1 at 4 km and 28 h−1 at 1 km. But in an area at ca. 1 km depth near carbonate and coral mounds the mean was 133 events h−1, much higher than predicted. In this bioluminescent hot spot 52–483 events h−1 were observed including moving luminescent targets and release of patches of luminescent material into the water around the bait so that on occasions the whole area around the bait was illuminated persisting on a time scale of minutes. At abyssal depths, luminescence was much less than reported at similar depths in the tropical NE Atlantic off Cape Verde. The sources of luminescence could not be determined but in the most active areas were associated with presence of eels Synaphobranchus kaupii which although themselves not luminescent may have stimulated luminescence from prey organisms such as ostracods (Vargula norvegica).  相似文献   
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Carbon in the Vegetation and Soils of Great Britain   总被引:1,自引:0,他引:1  
•The total amount of carbon held by vegetation in Great Britain is estimated to be 114 Mtonnes. •Woodlands and forests hold 80% of the G.B. total although they occupy only about 11% of the rural land area. Broadleaf species hold about 50% of the carbon in woodlands and forests. •A map of carbon in the vegetation of Great Britain at 1 km×1 km resolution based on land cover identified in the I.T.E. Land Cover Map is presented. The predominant location of vegetation carbon is the broadleaved woodlands of southern England. •The amount of carbon in the soils of Great Britain is estimated to be 9838 Mt (6948 Mt in Scotland and 2890 Mt in England and Wales). •In Scotland, most soil carbon is in blanket peats, whereas most soil carbon is in stagnogley soils in England and Wales. •The carbon content of the soils of Great Britain is mapped at 1 km×1 km resolution. Scottish peat soils have the greatest density of carbon and in total contain 4523 Mt of carbon, 46% of the G.B. total.  相似文献   
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