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561.
Abstract:  We assessed the extinction risks of Malagasy amphibians by evaluating their distribution, occurrence in protected areas, population trends, habitat quality, and prevalence in commercial trade. We estimated and mapped the distribution of each of the 220 described Malagasy species and applied, for the first time, the IUCN Red List categories and criteria to all species described at the time of the assessment. Nine species were categorized as critically endangered, 21 as endangered, and 25 as vulnerable. The most threatened species occur on the High Plateau and/or have been subjected to overcollection for the pet trade, but restricted extent of occurrence and ongoing habitat destruction were identified as the most important factors influencing extinction threats. The two areas with the majority of threatened species were the northern Tsaratanana-Marojejy-Masoala highlands and the southeastern Anosy Mountains. The current system of protected areas includes 82% of the threatened amphibian species. Of the critically endangered species, 6 did not occur in any protected area. For conservation of these species we recommend the creation of a reserve for the species of the Mantella aurantiaca group, the inclusion of two Scaphiophryne species in the Convention on the International Trade in Endangered Species Appendix II, and the suspension of commercial collecting for Mantella cowani . Field surveys during the last 15 years reveal no pervasive extinction of Malagasy amphibians resulting from disease or other agents, as has been reported in some other areas of the world.  相似文献   
562.
The most common technique used for numerical simulations of tracer mixing is that of the numerical solution of the advection–diffusion equation with the unresolved fluxes parameterized using the similarity theory. Despite correct predictions of the overall directions of transport, models based on a numerical solution of the advection–diffusion equation lack sufficient accuracy to correctly reproduce the coupling of mixing with small scale processes which are sensitive to the microstructure of the tracer distribution. The objective of this paper is to revisit the basic formalism employed in numerical models used to investigate atmospheric tracers. The main mathematical method proposed here is the theory of kinematics of mixing which could be applied effectively for simulations of atmospheric transport processes. At the beginning of the paper, we introduce simple mathematical transformations in order to demonstrate how complex topological structures are created by mixing processes. These idealistic flow systems are essential to explain transport properties of much more complex three-dimensional geophysical flows. An example of the application of the kinematics of mixing to the analysis of tracer transport on a planetary scale is presented in the following sections. The complex filamentary structures simulated in the numerical experiment are evaluated using some commonly applied statistical measures in order to compare the results with the data published in the literature. The results of the experiment are also analysed with the help of simple conceptual models of fluid filaments. The microstructure of the tracer distribution introduced in the paper is essential to increase our understanding of atmospheric transport and to develop more realistic parameterizations of small-scale mixing. The presented results could also be used to improve calculations of the coupling between microphysical processes and tracer mixing.  相似文献   
563.
2003年1-12月使用光离子化检测仪,对徐州市环境空气中的TVOC进行检测,监测结果显示:徐州市区环境空气中的TVOC浓度值1月份最高;其次为6月份;年平均值为82μL/m^3;交通干道两旁污染最严重。  相似文献   
564.
低负荷运行对城市污水生物除磷的影响   总被引:9,自引:0,他引:9  
针对目前国内较多的城市污水处理厂长期处于低负荷运转的状态,进行了现场生产性与静态模型的试验研究。结果表明,长期低负荷运行是导致生物除磷效率下降的主要原因。长期低负荷运行使聚磷菌微生物细胞内储存物质(PHB、Glycogen、poly-P等)含量下降,使生物除磷能力丧失。为了保证生物脱氮除磷处理系统的除磷效率,可通过调节生化反应容积、控制好氧区的曝气等手段,使处理系统的负荷控制在适合的范围内。  相似文献   
565.
本文提出了珠江广州段COD数值模拟的控制方程、计算格式、方法、步骤和程序,并结合野外实测资料进行了参数校正和验证计算。并根据计算和实测结果对珠江广州段COD污染的时空变化特点进行讨论。本文的主要特点是:(1)考虑了COD模型的各项影响,尤其是感潮河网涨退潮交替的不定常流影响;(2)提出了感潮河网不定常流条件下COD模型数值计算中的叉口处理,即关联任意个河段的叉口处受涨退潮影响的处理方法。  相似文献   
566.
刘珂  秦晓  韩柏平 《环境科技》2007,20(1):65-68
为了了解美国自来水行业消毒现状,在查阅了相关外文文献的基础上,对相关资料进行总结和分析.结果表明:氯气虽然仍是最广泛使用的消毒方式,但出于人们对健康安全的关注和许多饮用水法规的实施,使用氯气的水厂数量在不断减少.  相似文献   
567.
应用工业源复合短期模型(ISCST3)和ADMS-Urban模型来确定抚顺市空气中TSP浓度。结果发现:ISC-ST3模拟TSP与实测值的相关系数到达0.77;ADMS-Urban模拟TSP与实测值的相关系数到达0.85。同时确认的数据表明在抚顺地区运用模型模拟大气中污染物的方法是可行的。综合比较ISCST3模型和ADMS-Urban模型发现ADMS-Urban要优于ISCST3,在某些方面ISCST3还需要进一步的改进和改善。  相似文献   
568.
A probabilistic analysis of atmospheric transport and deposition patterns from two nuclear risk sites-Kamchatka and Vladivostok-situated in the Russian Far East to countries and geographical regions of interest (Japan, China, North and South Koreas, territories of the Russian Far East, State of Alaska, and Aleutian Chain Islands, US) was performed. The main questions addressed were the following: Which geographical territories are at the highest risk from hypothetical releases at these sites? What are the probabilities for radionuclide atmospheric transport and deposition on different neighboring countries in case of accidents at the sites? For analysis, several research tools developed within the Arctic Risk Project were applied: (1) isentropic trajectory model to calculate a multiyear dataset of 5-day forward trajectories that originated over the site locations at various altitudes; (2) DERMA long-range transport model to simulate 5-day atmospheric transport, dispersion, and deposition of 137Cs for 1-day release (at the rate of 10(10) Bq/s); and (3) a set of statistical methods (including exploratory, cluster, and probability fields analyses) for evaluation of trajectory and dispersion modeling results. The possible impact (on annual, seasonal, and monthly basis) of selected risk sites on neighboring geographical regions is evaluated using a set of various indicators. For trajectory modeling, the indicators examined are: (1) atmospheric transport pathways, (2) airflow probability fields, (3) fast transport probability fields, (4) maximum possible impact zone, (5) maximum reaching distance, and (6) typical transport time fields. For dispersion modeling, the indicators examined are: (1) time integrated air concentration, (2) dry deposition, and (3) wet deposition. It was found for both sites that within the boundary layer the westerly flows are dominant throughout the year (more than 60% of the time), increasing with altitude of free troposphere up to 85% of the time. For the Kamchatka site, the US regions are at the highest risk with the average times of atmospheric transport ranging from 3 to 5.1 days and depositions of 10(-1) Bq/m2 and lower. For the Vladivostok site, the northern China and Japan regions are at the highest risk with the average times of atmospheric transport of 0.5 and 1.6 days, respectively, and depositions ranging from 10(0) to 10(+2) Bq/m2. The areas of maximum potentially impacted zones are 30 x 10(4) km2 and 25 x 10(4) km2 for the Kamchatka and Vladivostok sites, respectively.  相似文献   
569.
While the effect of the safety gap on explosions is well known, little has been carried out to evaluate the effect of the safety gap on dispersion of gas releases, this paper evaluates the effect of safety gap on gas dispersion for a cylindrical Floating Liquefied Natural Gas (FLNG) vessel. The realistic ship-shaped and circular FLNG platforms are established and used for the detailed CFD based analysis; rather than the structural and hydrodynamics advantages of mobility, stability and cost efficiency etc., this study aims to investigate the safety of gas dispersion on the cylindrical FLNG and compare the safety gap effects on different configurations. A series of different safety gap configurations are evaluated for gas dispersion occurring in near field for the traditional FLNG while both near field and far field gas dispersion simulations are conducted on the cylindrical one. The overall results indicate that the safety gap is effective in reducing the gas cloud size in both FLNG configurations, however, when it comes to the gas dispersion in the far field against the leakage point, the safety gap increases the gas cloud size in the cylindrical FLNG vessel on the contrary.  相似文献   
570.
为调查长沙市大气中TVOC的分布特征及变化规律,研究其污染控制措施,按照相关标准和技术规范,在不同的功能区划和行政区划内合理布设12个监测点位,分季节采集样品,使用热脱附-气相色谱法进行检测,利用反距离权重插值和遥感解译等方法进行综合分析。结果表明:长沙市大气中苯与甲苯( B/T)特征比值为0.58,汽车尾气是长沙市苯系物和TVOC的主要来源;长沙市不同的工业区TVOC浓度有显著差异,工业区合理布局,增加绿化面积,可以有效的降低TVOC浓度。  相似文献   
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