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排序方式: 共有1016条查询结果,搜索用时 31 毫秒
831.
我国核能利用与能源可持续发展探讨 总被引:1,自引:0,他引:1
阐述了我国目前的能源利用状况,火电与核电对环境影响的比较,核废物的处理技术及核电的安全性等,指出大力发展高效清洁的核电是我国实施可持续发展战略的必然要求。 相似文献
832.
833.
中国酸雨的生态影响和防治对策 总被引:33,自引:0,他引:33
我国是继欧洲、北美之后 ,在世界上出现的第三大酸雨区。长江以南各省是我国酸雨的主要分布区。酸雨对生态系统的危害日益严重。本文阐述了酸雨对农作物、森林和人体健康的影响。并根据可持续发展的战略思想 ,提出防治对策。 相似文献
834.
水分管理与秸秆施用对稻田CH4和N2O排放的影响 总被引:30,自引:0,他引:30
2000年6~10月在南京近郊江宁区实施大田试验.主要研究了水稻生长季常规灌溉和连续淹水条件下有机质(小麦秸杆)不同施用量(0,2.25,4.5t/hm2)对稻田CH4和N2O排放的影响.结果表明,在连续淹水条件下,CH4排放量与秸杆施用量成正比,N2O排放与秸杆施用量成反比.烤田的N2O的排放量在施用2.25t/hm2秸杆与对照之间无明显差异,但施用4.5t/hm2秸杆处理其N2O的排放量仅为对照或施用2.25t/hm2秸杆处理下的13%左右.综合考虑水稻生长季CH4和N2O排放的全球增温潜势(GWP),在增加有机质的施用量(如按4.5t/hm2施用量秸杆还田)的情况下,烤田的GWP只占连续淹水处理的60%,是减少稻田CH4和N2O综合温室效应的一种有效措施. 相似文献
835.
Wichmann H Sprenger R Ehlers N Bahadir MA 《Environmental science and pollution research international》2005,12(4):227-232
Background, Aims and Scope Releasing agents, applied in the aluminium diecasting process, usually consist of water, oils, waxes, polysiloxanes, as well
as of a set of additives like emulsifiers, corrosion inhibitors, and biocides. During spray application and part release,
gases and aerosols are emitted into workplace air. The chemical compositions of these emissions are determined by the components
of the releasing agents and their reaction products formed during thermal stress of more than 700 °C. In the frame of the
joint project, the analytical tasks were to develop an appropriate sampling strategy for this production environment, to draw
conclusions about the occurrence of hazardous chemicals from production plant studies and from laboratory-scale thermolysis
experiments, and to determine the biodegradability of customary releasing agents.
Methods During realistic test production, active air sampling was performed in a production hall using different adsorption materials.
Cotton fabric sheets were positioned in the production area as passive samplers. Thermolysis experiments were performed at
600 °C with sealed quartz ampoules. The biodegradability of different releasing agents was determined according to German
industry standard DIN 51828 (2000). For analyses, GC/MS (headspace), FTIR, HPLC, IC, and ICP-OES techniques were applied.
Results and Discussion The substance spectrum, which was found in workplace air, was dominated by saturated and non-saturated aliphatic hydrocarbons.
Besides these, alcohols, alkyl phenols, xylenes and other benzene derivatives, aldehydes, glycols, carboxylic acid esters,
and amides were present. The German limiting value of 40 mg/m3 of complex hydrocarbon mixtures in a diecasting workplace atmosphere
was clearly under-run. Total hydrocarbon contents ranged between 2.7 and 6.3 mg/m3. Five different PAH were found in the air
close to the diecasting machine, with maximum concentrations between 0.05 and 3.06 μg/m3. Concentrations of nonylphenols ranged
from 10 to 200 μg/m3, and those of triethanolamine from 20 to 30 μg/m3. From 17 elements analyzed, only B, Fe, P, S, Si, and
Ti were emitted in small amounts. It was striking that the PAH patterns resulting from thermolysis experiments were quite
the same compared to those determined during the diecasting process. An influence of water and of Fe/Al on the composition
of the thermolysis products could mostly be shown. The degrees of biodegradation of three releasing agent extracts after 21
days were 21%, 29%, and 55%, respectively.
Conclusion A sampling strategy was developed, which allows an emission assessment for the industrial process of aluminium diecasting.
It enabled one to control limiting values, to characterise a wide variety of compounds emitted, and to identify and quantify
relevant pollutants. Only a few hazardous substances could be detected during the exemplary use of one releasing agent within
the compounds emitted into workplace air. Indications were found, that the prediction of the formation of harmful substances
from releasing agent components should be possible via thermolysis experiments. The biodegradability test can serve to assess
the expenditure of disposal of the usual leakage run-off of excess agent during production.
Recommendation and Outlook Investigations on further differently composed releasing agents, e.g. powders, would be desirable. A substitution of nonylphenol
ethoxylates by less harmful components would surely be an improvement of a releasing agent with regard to work safety and
health care, because of avoiding the emission of toxic and endocrine active nonylphenols. The surprisingly wide range of biodegradability
of the investigated releasing agents points to an optimization potential, that has obviously not yet been considered. 相似文献
836.
837.
Sperm traits often show extreme variation both between and within species. Between-species variation may often be interpreted
in the context of a sperm competition theory, but within-species variation has remained unexplained. Previous studies on intraspecific
variation in sperm traits have focused on a limited set of variables and may have failed to explain observed variation because
of potential trade-offs between different sperm traits. We report on variation in number, size, motility and longevity of
sperm in the frog Crinia georgiana, a species where sperm competition is common. We found intrapopulation variation in sperm size and motility and interpopulation
variation in relative sperm number and size. When we combined relative sperm number and size into one variable, and motility
and longevity into another, we found significant interpopulation variation in these variables as well. We also detected considerable
intra- and significant interpopulation variation in cumulative sperm quality, a combination of all four sperm traits. Furthermore,
a significant effect of the interaction between population origin and male size on sperm characteristics indicated interpopulation
variation in the strength of selection acting on sperm traits of males adopting different mating strategies. We discuss heterogeneity
in the reproductive environment, a complex genetic background in the determination of sperm characteristics and varying levels
of developmental noise as potential contributors to the observed variation in sperm traits. 相似文献
838.
本文从会计数字游戏产生的根源着手,分析了上市公司会计数字游戏滋生的内、外部条件及诱因,进而分析如何才能够减少会计数字游戏. 相似文献
839.
揭阳市生态农业发展的思路 总被引:1,自引:0,他引:1
分析了揭阳市生态农业发展的现状、有利条件及制约囚素,总结了对该市发展生态农业有积极影响的揭东县塔西种养场生态种养模式,最后提出了该市生态农业的发展模式、发展思路和对策。 相似文献
840.
吐鲁番盆地的生态灾害具有种类多、危害面广、危害程度深等特征,并严重制约着该区绿洲经济的持续稳定发展。本文分析了每种生态灾害发生的原因、危害程度及地区分布,并提出了生态灾害调控的基本原则;综合整体性、区域分异性、持续性.最后探讨了该地生态灾害调控的一些具体措施。 相似文献