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461.
Nicole Stelzer Martin Thullner Alexander Poser Ivonne Nijenhuis 《Environmental pollution (Barking, Essex : 1987)》2009,157(6):1800-1806
Biodegradation of chlorobenzenes was assessed at an anoxic aquifer by combining hydrogeochemistry and stable isotope analyses. In situ microcosm analysis evidenced microbial assimilation of chlorobenzene (MCB) derived carbon and laboratory investigations asserted mineralization of MCB at low rates. Sequential dehalogenation of chlorinated benzenes may affect the isotope signature of single chlorobenzene species due to simultaneous depletion and enrichment of 13C, which complicates the evaluation of degradation. Therefore, the compound-specific isotope analysis was interpreted based on an isotope balance. The enrichment of the cumulative isotope composition of all chlorobenzenes indicated in situ biodegradation. Additionally, the relationship between hydrogeochemistry and degradation activity was investigated by principal component analysis underlining variable hydrogeochemical conditions associated with degradation activity at the plume scale. Although the complexity of the field site did not allow straightforward assessment of natural attenuation processes, the application of an integrative approach appeared relevant to characterize the in situ biodegradation potential. 相似文献
462.
463.
中国雨日变化趋势的分形研究 总被引:3,自引:0,他引:3
利用1951-2002年中国752个台站的雨日资料,运用分形理论和R/S分析法,研究并预测了中国五大降水区年雨日的气候变化趋势.研究表明:中国五大降水区未来的年雨日变化趋势与过去50a的变化有着很好的自相似性.为了更深入研究雨日的未来的变化,设计了两项Hurst指数试验,用两项试验结果与年雨日年际变化趋势的对应关系来推断未来的变化趋势及其转折与突变.结果表明:中国五大降水区年雨日有着一致的减少趋势,但其变化呈现显著的地域分异特征.依照五大降水区的气候倾向率,西北区、西南区、青藏高原区、东部北方区、东部南方区未来平均每10a雨日减少分别为4.1d,11.4d,3.7d,6.8d和5.9d,其中西南区年雨日减少最多.期间,中国五大降水区虽有气候变化的转折,但不存在雨日气候变化的突变点. 相似文献
464.
Southern California desert public lands receive especially high levels of off-highway recreation due to large population centers
nearby and popular riding environments such as sand dunes. Controversy has developed over the flat-tailed horned lizard (Phrynosoma mcallii), previously a candidate for listing under the Endangered Species Act. Some evidence suggests lower lizard abundance in areas
of higher recreational use than in areas with low or no use. We designed a manipulative experiment to ensure maximum inference
in evaluating the direct impact of recreational riding of off-highway vehicles on lizards. Thirty-six lizards, in situ, were
treated with an off-highway vehicle treatment during hibernation season in three treatment groups: high impact, low impact,
and control. Treatments consisted of timed riding by off-highway vehicles. In all treatment groups survival was 100%, despite
hibernation of lizards at very shallow depths. Consequently, indirect effects of off-highway vehicles deserve increased attention.
The relative importance of direct versus indirect (i.e., degradation of lizard habitat) impacts caused by off-highway vehicles
remains unknown. These indirect effects may include the altering of vegetation, substrate, and prey. We recommend that a manipulative
approach be adopted to investigate these possibilities. 相似文献
465.
掘进巷道瓦斯分布数值实验研究 总被引:5,自引:1,他引:4
根据局部通风流场特点确定适合矿井局部通风掘进巷道工作面瓦斯与风流质量交换的数学模型,在近壁面使用标准壁面函数法解决近壁面的流动,在湍流充分发展区,使用RNG k-ε双方程湍流模型;讨论考虑巷道支护的情况下壁面粗糙度的影响,确定矿井掘进工作面局部通风模型网格划分的方法、掘进头瓦斯涌出的边界条件;利用计算流体力学(CFD)软件Fluent对掘进工作面的风流与瓦斯的混合过程进行了模拟;得出不同瓦斯涌出量情况下掘进巷道工作面风流分布和瓦斯浓度的分布规律。研究表明:瓦斯涌出量和风速对流场分布有影响,随着瓦斯涌出量的增大和风速的降低,瓦斯对流场的影响越来越明显。 相似文献
466.
Masto RE Chhonkar PK Singh D Patra AK 《Environmental monitoring and assessment》2008,136(1-3):419-435
Soil quality assessment provides a tool for evaluating the sustainability of alternative soil management practices. Our objective
was to develop the most sensitive soil quality index for evaluating fertilizer, farm yard manure (FYM), and crop management
practices on a semiarid Inceptisol in India. Soil indicators and crop yield data from a long-term (31 years) fertilizer, manure,
and crop rotation (maize, wheat, cowpea, pearl millet) study at the Indian Agricultural Research Institute (IARI) near New
Delhi were used. Plots receiving optimum NPK, super optimum NPK and optimum NPK + FYM had better values for all the parameters
analyzed. Biological, chemical, and physical soil quality indicator data were transformed into scores (0 to 1) using both
linear and non-linear scoring functions, and combined into soil quality indices using unscreened transformations, regression
equation, or principal component analysis (PCA). Long-term application of optimum inorganic fertilizers (NPK) resulted in
higher soil quality ratings for all methods, although the highest values were obtained for treatment, which included FYM.
Correlations between wheat (Triticum aestivum L.) yield and the various soil quality indices showed the best relationship (highest r) between yield and a PCA-derived SQI.
Differences in SQI values suggest that the control (no NPK, no manure) and N only treatments were degrading, while soils receiving
animal manure (FYM) or super optimum NPK fertilizer had the best soil quality, respectively. Lower ratings associated with
the N only and NP treatments suggest that one of the most common soil management practices in India may not be sustainable.
A framework for soil quality assessment is proposed. 相似文献
467.
468.
具有超压/负压防护功能的急救车防生物污染的安全性试验研究 总被引:6,自引:1,他引:5
采用粘质沙雷菌气溶胶,对具有超压/负压防护功能的急救车防生物污染的安全性进行试验考核。分别测试气溶胶发生后30s,1min,5min,10min时,车厢在超压防护和负压防护下的过滤效率,其结果表明:急救车在超压防护状态下开启空调时的平均过滤效率能达到99.99%,不开空调时的平均过滤效率能达到99.95%;在负压防护状态下开启空调时的平均过滤效率能达到99.93%,不开空调时的平均过滤效率能达到99.95%。证明急救车能够通过生物污染区域安全运送、急救伤病员,也能够运送、急救生物污染伤病员或烈性传染病员确保沿途环境不受污染,该研究成果为应对生物恐怖袭击和突发公共卫生事件(烈性传染病)提供了一种安全可靠的机动医疗救治平台。 相似文献
469.
Richard M. Bennett Ken G. Willis 《Journal of Environmental Planning and Management》2008,51(4):511-523
This paper applies an attribute-based stated choice experiment approach to estimate the value that society places on changes to the size of the badger population in England and Wales. The study was undertaken in the context of a rising incidence of bovine tuberculosis (bTB) in cattle and the government's review of current bTB control policy. This review includes consideration of culling badgers to reduce bTB in cattle, since badgers are thought to be an important wildlife reservoir for the disease. The design of the CE involved four attributes (size of badger population, cattle slaughtered due to bTB, badger management strategy and household tax) at four levels with eight choice sets of two alternatives presented to respondents. Telephone interviews were undertaken with over 400 respondents, which elicited their attitudes and preferences concerning badgers, bTB in cattle and badger management strategies. The study estimated a willingness to pay of £0.10 per household per year per 100,000 badgers and £1.52 per household per year per 10,000 cattle slaughtered due to bTB which aggregated to £22 per badger and £3298 per bTB slaughtered animal for all households in England and Wales. Management strategy toward badgers had a very high valuation, highlighting the emotive issue of badger culling for respondents and the importance of government policy towards badgers. 相似文献
470.
Investigating household preferences for kerbside recycling services in London: a choice experiment approach 总被引:2,自引:1,他引:1
Recent developments in national and European Union waste management policy have prompted considerable interest in alternative waste management programs, such as recycling, which could divert a portion of the municipal solid waste stream from landfills. This paper examines household preferences for kerbside recycling services and uses a stated preference choice experiment method to estimate households' valuation of such services. Using a sample of 188 households in the London area, the empirical analysis yields estimates of the willingness to pay for the number of 'dry' materials collected, the collection of compost, textile collection and the frequency of collection. 相似文献