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81.
Model oligo esters of terephthalic acid with 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol have been investigated with regard to their biodegradability in different biological environments. Well-characterized oligomers with weight-average molar masses of from 600 to 2600 g/mol exhibit biodegradation in aqueous systems, soil, and compost at 60°C. SEC investigations showed a fast biological degradation of the oligomer fraction consisting of 1 or 2 repeating units, independent of the diol component used for polycondensation, while polyester oligomers with degrees of polymerization higher than 2 were stable against microbial attack at room temperature in a time frame of 2 months. At 60°C in a compost environment chemical hydrolysis also degrades chains longer than two repeating units, resulting in enhanced degradability of the oligomers. Metabolization of the monomers and the dimers as well by the microorganisms could be confirmed by comparing SEC measurements and carbon balances in a Sturm test experiment. Based on these results degradation characteristics of potential oligomer intermediates resulting from a primary chain scission from copolyesters consisting of aromatic and aliphatic dicarbonic acids can be predicted depending on their composition. These results will have an evident influence on the evaluation of the biodegradability of commercially interesting copolyesters and lead to new ways of tailor-made designing of new biodegradable materials as well. 相似文献
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Public Perception of Flood Hazard in the Niger Delta,Nigeria 总被引:3,自引:0,他引:3
Summary Our study had the aim of understanding how floodplain dwellers regard the risk of flooding. About 500 questionnaires were
administered to landowners in the selected settlements in the study area using systematic random sampling. The results of
analysis show, among other things, that the population regards most important the causes of floods as heavy, prolonged rainfall
and river overflow. Nevertheless, they have little knowledge of the frequency of severe floods, and flood alleviation schemes.
Most flood victims do not get compensation or relief during flood disaster, and the reason why they remain in the study area
is influenced by their occupations, especially fishing, subsistence agriculture, and the presence of crude oil in the region
which has attracted many migrants who cannot afford the high cost of accommodation and are therefore forced to live in vulnerable
areas of the floodplain. Finally, the study concludes that flood control in the region needs the cooperation of government,
community efforts and an enlightenment programmes through environmental education and mass media. 相似文献
85.
A study of a watershed planning process in the Cache River Watershed in southern Illinois revealed that class divisions, based
on property ownership, underlay key conflicts over land use and decision-making relevant to resource use. A class analysis
of the region indicates that the planning process served to endorse and solidify the locally-dominant theory that landownership
confers the right to govern. This obscured the class differences between large full-time farmers and small-holders whose livelihood
depends on non-farm labor. These two groups generally opposed one another regarding wetland drainage. Their common identity
as “property owner” consolidated the power wielded locally by large farmers. It also provided an instrument – the planning
document – for state and federal government agencies to enhance their power and to bring resources to the region. The planning
process simultaneously ameliorated conflicts between government agencies and the large farmers, while enhancing the agencies’
capacity to reclaim wetlands. In this contradictory manner, the plan promoted the environmental aims of many small-holders,
and simultaneously disempowered them as actors in the region’s political economy.
An erratum to this article is available at . 相似文献
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Gaverick?Matheny Kai?M.?A.?ChanEmail author 《Journal of Agricultural and Environmental Ethics》2005,18(6):579-594
Few moral arguments have been made against vegetarian diets. One exception is the “Logic of the Larder:” We do animals a favor
by purchasing their meat, eggs, and milk, for if we did not purchase these products, fewer animals would exist. This argument
fails because many farm animals have lives that are probably not worth living, while others prevent a significant number of
wild animals from existing. Even if this were not so, the purchase of animal products uses resources that could otherwise
be used to bring a much greater number of animals into existence. 相似文献
89.
Laboratory leaching tests may be used for source term determination as a basis for risk assessment for soil-groundwater pathways on contaminated sites. In order to evaluate different leaching procedures, batch extraction tests and percolation tests were performed using three reference materials produced from contaminated soil, demolition waste and municipal solid waste incinerator bottom ash. Emphasis was placed on the investigation of the leachability of the heavy metals copper and chromium, polycyclic aromatic hydrocarbons (PAHs) and the anions chloride and sulfate. Significant discrepancies between column experiments and batch/extraction tests were found for the release of PAHs and to a lesser extent for the heavy metals Cu and Cr. Additionally interlaboratory comparisons were conducted based on different leaching tests with the reference materials and evaluated using the criteria of comparability and reproducibility. The best reproducibility was achieved for all investigated substances in column tests. The reproducibility of batch tests was acceptable except for PAHs. The results from the experimental work will help establish standardized and feasible laboratory procedures as fundamental for substance specific risk assessment of contaminated sites. 相似文献
90.
It is a great challenge to sample seawater across interfaces, for example the halocline or the redoxcline, to investigate trace metal distribution. With the use of 10l sampling bottles mounted to a wire or a CTD-Rosette it is possible to obtain a maximum vertical resolution of 5m. For the detection of small vertical structures in the vertical distribution of trace metals across the redoxcline, the CTD-Bottle-Rosette is not sufficient. Therefore, a PUMP-CTD-System was developed, which enables water sampling with high resolution (1m maximum) along a vertical profile. To investigate the suitability and possible contamination sources of this device two experiments were carried out in the Gotland Basin. The first experiment consisted of two separate profiles. The first profile was obtained with the CTD-Bottle-Rosette and the second with the PUMP-CTD-System. Both were taken from the bottom to the surface water layer. The second experiment was a combined profile obtained from the surface to the bottom with the PUMP-CTD-System attached to the CTD-Bottle-Rosette. Concentrations of dissolved Pb, Cd, Cu, Zn, Fe, Mn, Co and Ni from the "Niskin Bottles" and from the PUMP were measured and compared for each investigation. We demonstrate that it is useful to perform vertical sampling from lower to higher concentrations, e.g. surface to bottom in this environment, and that a longer flushing is required for sampling seawater in the anoxic bottom water. A comparison of the two systems for oxygen and hydrogen sulphide measurements showed an improvement of the precision and the quality of the sampling when using the PUMP. Thus, metal speciation at the oxic-anoxic gradient zone and on a high vertical resolution will be accessible. As concentrations of dissolved Pb, Cd, Cu, Zn, Co, Ni, Fe and Mn in seawater sampled with both devices were in the same range, we conclude that the PUMP-CTD-System is well suited to sample seawater for trace metal analyses. 相似文献