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481.
Fabíola Maria N. Nunes M.C.C. Veloso P.A. de P. Pereira J.B. de Andrade 《Atmospheric environment (Oxford, England : 1994)》2005,39(40):927
Biogenic emissions of volatile organic compounds (VOCs) play a fundamental role in atmospheric chemistry. Vegetation is the most abundant natural source of VOCs, while terpenoids, as limonene, α and β pinene and mircene, top the plants emission list. Much interest has been demonstrated in oxidation and photooxidation reactions of VOCs, particularly of monoterpenoids, owing to their diversity and to uncertainties regarding their mechanism of reaction. Quantification of primary carbonylic compounds, as well as of biradical reaction components, is highly relevant to the understanding of the major reactions. In this context, taking into account both structural factors and the fact that these compounds are found in the essential oils of plants typically found in Brazil and that they may be present in the atmosphere from emission by the plants, the monoterpenoids (S)-(+)-carvone, (R)-(−)-carvone, (−)-carveol, geraniol and citral (a mixture of the isomers geranial and neral) were selected for this study.The ozonolysis reactions of the monoterpenoids were carried out under dark conditions for all experiments, due to their photochemical reactivity. The analysis of the results lets us propose a mechanism by which these reactions occur. The observed results of the ozonolysis of S and R carvone suggest that the stereochemistry of asymmetric carbon does not affect either in the yields of both formaldehyde and of OH radicals produced in the reaction, or in the reactivity of these compounds, for which the rate constants were in the scale of 10−6 s−1.We found that, in the (−)-carveol's cis and trans mixture, even though the hydroxyl in the axial position—in the case of trans-(C) and cis-(D′) isomers—favors the attack by the ozone molecule on the external double bond, thus increasing the mixture's reactivity , it affects the average production of formaldehyde. The presence of geraniol and citral led to the production of formaldehyde, propanone, glyoxal, methyl–glyoxal and cyclohexanone (OH radicals) as reaction products. The influence of an electron attractor group bonded to the carbon of the double bond, on the reactivity of the double bond, could not be observed in the case of citral, due to strong interference occurring in the instrument in all experiments with this monoterpenoid. For this reason, only the kinetics of geraniol was monitored . 相似文献
482.
Creating and restoring wetland and riparian ecosystems between farms and adjacent streams and rivers in the Upper Mississippi River Basin would reduce nitrogen loads and hypoxia in the Gulf of Mexico and increase local environmental benefits. Economic efficiency and economic impacts of the Hennepin and Hopper Lakes Restoration Project in Illinois were evaluated. The project converted 999 ha of cropland to bottomland forest, backwater lakes, and flood‐plain wetland habitat. Project benefits were estimated by summing the economic values of wetlands estimated in other studies. Project costs were estimated by the loss in the gross value of agricultural production from the conversion of corn and soybean acreage to wetlands. Estimated annual net benefit of wetland restoration in the project area amounted to US$1,827 per ha of restored wetland or US$1.83 million for the project area, indicating that the project is economically efficient. Impacts of the project on the regional economy were estimated (using IMPLAN) in terms of changes in total output, household income, and employment. The project is estimated to increase total output by US$2,028,576, household income by US$1,379,676, and employment by 56 persons, indicating that it has positive net economic impacts on the regional economy. 相似文献
483.
Tony Prato 《Journal of the American Water Resources Association》2003,39(4):935-946
ABSTRACT: The technocratic approach for managing the Missouri River and other large rivers is not effective in resolving conflicts among competing uses of water and dealing with uncertainty about how river ecosystems respond to alternative management actions. Adaptive management offers an alternative way to address these and other issues. It has the potential to alleviate management gridlock and provide lasting solutions to management of the Missouri River and other large river ecosystems. In passive adaptive management, simulation models and expert judgment are combined to select a preferred management action. While passive adaptive management is relatively simple and inexpensive to use, it does not necessarily provide reliable information for making management decisions. Active adaptive management uses statistically designed experiments to test assumptions or hypotheses about ecosystem responses to management actions. It is best carried out by a collaborative working group. Active adaptive management has several advantages, but the inability to satisfy certain prerequisites for successful application makes it more difficult to implement in large river ecosystems. A second‐best approach is proposed here to select, implement, monitor, and evaluate a preferred management action and retain that action provided ecological conditions improve and socioeconomic indicators do not fall below established acceptability limits. 相似文献
484.
This paper explores the nature of tri-sector partnerships applied to community development in the mining sector. The case study approach was used to examine an initiative for environmental improvement and socio-economic development in the diamond province of the Republic of Sakha (Yakutia), in the Russian Federation. The study follows the journey of this initiative from a potential tri-sector partnership model between the diamond mining company ALROSA, the Government of the Republic of Sakha (Yakutia) and the SAPI Foundation, to a bi-lateral partnership between ALROSA and the Government represented by the Target Fund. The study explores the community development in the diamond province in the light of economic and political transition within the mining sector of the Russian Federation. 相似文献
485.
Susana L. H. Rebelo A. Melo R. Coimbra M. Emília Azenha Mariette M. Pereira Hugh D. Burrows Mohamed Sarakha 《Environmental Chemistry Letters》2007,5(1):29-33
The photodegradation of the herbicides atrazine and ametryn with visible light in aerated neutral aqueous solutions and 5,
10, 15, 20-tetrakis (2,6-dichloro-3-sulfophenyl) porphyrin or 5, 10, 15, 20-tetrakis (4-sulfophenyl) porphyrin as sensitizers
are reported for the first time. Our findings show that the degradation percentage reached 30% for atrazine and 63% for ametryn.
The final photoproducts were characterized as dealkylated s-triazines. Photolysis of the pesticides in the presence of a singlet oxygen quencher showed only a minor contribution of
this type of mechanism, while a bimolecular quenching reaction between the triplet state of the sensitizer and the pesticides
is excluded by flash photolysis studies. It is proposed that the mechanism may involve the formation of a superoxide radical
anion from the triplet state of the sensitizer and molecular oxygen, followed by a radical decomposition pathway.
Selected article from 1st International Meeting on Photochemistry, Photocatalysis and Environmental Applications, Agadir,
2006, organised by Prof. Dr. Ait Ichou, University Ibn Zohr, Agadir, Morocco 相似文献
486.
487.
Maria do Socorro S. Pereira Eduardo Winter Jose Roberto Guimarães Susanne Rath Anne Hélène Fostier 《Environmental Chemistry Letters》2007,5(3):137-141
Here, we show a fast and sensitive method for the determination of inorganic arsenic in natural waters using differential
pulse cathodic stripping voltammetry. All the arsenite determinations were done in 2.0 mol L−1 HCl + 3.15 × 10−4 mol L−1 Cu(II) supporting electrolyte. 1 × 10−3 mol L−1 sodium thiosulphate was used as As(V) reducing agent. The detection limit was 0.5 μg L−1 for both species. The method has been applied to water samples collected in an arsenic-contaminated region of Brazil, in
particular, to verify the efficiency of the solar oxidation and removal of arsenic process applied to these waters. 相似文献
488.
Tony Jones 《Local Environment》1996,1(1):87-106
Local authorities are increasingly undertaking policy initiatives which aim to achieve local sustainability. Indeed, the rapid development in this area since its first tentative steps in the late 1980s is very impressive. However, it is legitimate to question whether any real progress has been made in improving local environmental conditions. This is almost impossible to determine as very few have translated policy rhetoric into measurable environmental achievement. Although the development of sustainability indicators will, in the long term, provide some means of measuring success, few authorities have the necessary precursor for its achievement in place: performance-based environmental programmes. This important stage of development has been all but missed in the rush for national and international credibility, often at the expense of local communities and their environment rather than for their benefit. This paper examines the activities of one local authority, the London Borough of Hackney, and its efforts to translate policy principals into practical Action for the Environment through the mechanism of performance review. It is concluded that performance review has a valuable role to play in achieving environmental improvements to help move society towards sustainability but, like any mechanism, there are limitations in its use which need to be acknowledged if it is to be used effectively. These are explored in detail in the paper in the hope that they assist others when developing similar performance-based environmental programmes. 相似文献
489.
Harold G. Fowler Maria Inez Pagani Osvaldo Aulino Da Silva Luis Carlos Forti Virgilio Pereira Da Silva Heraldo Luis De Vasconcelos 《Environmental management》1989,13(6):671-675
Leaf-cutting ants of the generaAcromyrmex andAtta are considered the principal polyphagous pests of the Neotropics Although some members of these genera are of economic importance, have a broad geographic distribution, and are extremely good colonizers, others are endemic and closely interact with native ecosystems. Control is generally practiced against any colony, irrespective of its taxonomic status. Indiscriminate control coupled with habitat destruction threatens endemic species with extinction, and, through habitat simplification, favors other pest species. As nests ofAtta are large, having several square meters of nest surface, the endemic taxa can be easily used as environmental indicators for natural ecosystems Likewise, the pest species can be used to detect environmental disturbance As these ants are keystone species and easily identified by nonspecialists, efforts should be made to integrate these into viable conservation programs 相似文献
490.
Helen Carnaghan Catherine P. James Paul B. Charlesworth Marco Ghionzoli Susana Pereira Mohamed Elkhouli David Baud Paolo De Coppi Greg Ryan Prakesh S. Shah Mark Davenport Anna L. David Agostino Pierro Simon Eaton Gastroschisis Study Group 《黑龙江环境通报》2020,40(8):991-997