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881.
本文运用人类生态学原理,建立了天津城市区生活质量评价的指标体系。基于这一指标体系,采用居民满意度分析方法,剖析了旧城区居民生活质量的主要问题,探讨了天津旧城改造与重建中生活质量调控性规化指标,提出了旧城改造与重建的对策性建议。  相似文献   
882.
试论资源战略   总被引:2,自引:1,他引:2  
本文从资源战略研究的两个相互联系的方面展开讨论,第一部分论述了资源战略评价的基本公式与三大要点,即总体评价、相关评价和潜力评价;第二部分首次提出资源战略决策的程序,包括开发利用方向、开发利用规模、开发利用布局、开发利用时序、开发利用方式和资源保护等不同层次的内容,构成资源开发决策的完整体系。全文系统地阐述了资源战略研究的中心内容和基本方法,客观地反映了资源战略研究的规律性。  相似文献   
883.
维护名牌可持续性应坚持针对性、互补性和最佳力度3个原则,以清洁产品和环境标志为重要手段,在生产过程中切实进行清洁生产审计,谋求以资源持续有效利用和环境保护为前提的效益增长。  相似文献   
884.
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   
885.
能源投资收益率的研究进展及其应用前景   总被引:4,自引:0,他引:4  
文章介绍了能源投资收益率(EROI指数)的概念--能源生产过程中能源产出和能源消耗的比值,引入了能源质量因子的概念,并以此为理论依据介绍了能源投资收益率的计算方法.文章综述了近些年国际上对能源投资收益率的研究进展,及其在宏观和微观层面能源经济分析上的运用实例,并运用能源投资收益率对中国1991至1999年的煤炭和石油天然气行业进行了能源经济分析,指出了中国能源行业现存的一些问题,最后展望了其在中国能源经济评价和能源战略制定中的应用前景.  相似文献   
886.
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   
887.
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   
888.
本文对2018年2月采自东海鱼外渔场的海洋生物(包括鱼类、头足类和甲壳类)体内的5种重金属(Cu、Pb、Cr、As、Cd)和16种多环芳烃(PAHs)的残留水平进行了测定,分析了污染物在生物体内的累积特性并计算了潜在的食用风险,并结合氮稳定同位素技术,初步探讨了生物体内重金属和PAHs的营养级传递特性。结果表明:5种重金属在生物中的平均浓度表现为CuPbCrAsCd;参照我国《食品中污染物限量》和《无公害食品水产品中有毒有害物质限量》,重金属Cu、Cd和Cr均未超过食用标准,但Pb和As的超标现象较为严重。与世界其他范围海域生物体内重金属浓度相比,该渔场生物体内Cu和Pb浓度较高。∑PAHs的平均浓度为283 ng·g~(-1)dw,以低环PAHs(2~3环)占比较大,且主要贡献单体为萘(NAP),总体处于较低污染水平。海洋生物对重金属的富集能力较PAHs高,尤其对Cu的富集最为明显。但风险计算结果表明,重金属和PAHs都不会对消费者的人体健康产生明显风险。重金属Cu和Cd浓度随营养级的升高出现了稀释现象,但重金属Pb、Cr、As和PAHs的营养传递特性不明显,覆盖完整食物链的污染物营养传递特性有待进一步深入研究。  相似文献   
889.
890.
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   
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