Dynamique des populations de Tisbe holothuriae (Crustacea: Copepoda) en élevage sur trois régimes artificiels différents

The influence of three different artificial diets (Tetramin, Bioter food and Renutryl) on the life cycle of Tisbe holothuriae Humes, 1957 has been investigated under constant experimental conditions (19°C; 38 S). Females (F2) whose life history has been followed, were obtained from a common mother (F1). They were bred in 50 ml dishes and transferred into a fresh container as soon as they produced a new egg-sac. Offspring (F3) resulting from successive egg-layings were counted as soon as they moulted into adults. Larval mortality was estimated in two ways: (1) by enumeration of adults issuing from a known number of nauplii; (2) by comparison of the average number of eggs from egg-sacs of F2 with the average number of adult offspring F3. The life-span of F2 females, including the larval stages, varies between 23.6 days (Renutryl diet) and 33.4 days (Tetramin diet). The first egg-sac appears about 12 days after hatching, whatever diet is used. The first copulation immediately follows the last moult, about 8 days after hatching. The reproductive period lasts for 6.5 (Renutryl) to 10.4 days (Bioter). The average number of successive egg-sacs laid is minimal with Renutryl (3.7) and maximal with Tetramin (5.1), but actual egg production is higher with Renutryl (86 eggs/sac) than with Bioter (67) or Tetramin (58). Nevertheless, as a result of varying larval mortality with the different diets, eventual numbers of adult F3 obtained are significantly higher with Bioter (310) than with Tetramin and Renutryl (216 and 188, respectively). The offspring F3 sex-ratio varies in successive broods and with the nature of the food offered: more females are produced with Bioter or Renutryl than with the Tetramin diet. Then net reproduction rate, R ₀, is higher with Bioter, because of the low larval mortality, high fertility, and high ratio of females resulting from this diet. The intrinsic rate of natural increase (r _m) is similar with Renutryl and Bioter diets (0.298 and 0.301, respectively), a lower value (0.260) occurs with the Tetramin diet. These different values are discussed and compared with previous data for Tisbe species fed natural diets.     

A two-dimensional model for simulating the transport and fate of toxic chemicals in a stratified reservoir

A two-dimensional reservoir toxics model is essential to establishing effective water resources management and protection. In a reservoir, the fate of a toxic chemical is closely connected with flow regimes and circulation patterns. To better understand the kinetic processes and persistence and predict the dissipation of toxic contaminants in the reservoir during a spill or storm runoff event, a toxics submodel was developed and incorporated into an existing laterally integrated hydrodynamics and transport model. The toxics submodel describes the physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions of a toxic chemical. The two-dimensional toxicant simulation model was applied to Shasta Reservoir in California to simulate the physico-chemical processes and fate of a volatile toxic compound, methyl isothiocyanate (MITC), during a chemical spill into the Sacramento River in 1991. The predicted MITC concentrations were compared with those observed. The effect of reservoir flow regimes on the transport and fate of the toxic substance was investigated. The results suggested that the persistence of MITC is significantly influenced by different flow regimes. Methyl isothiocyanate is more persistent in the reservoir under an interflow condition due to reduced volatilization from deep layers than under an overflow condition. In the overflow situation, the plume moved more slowly toward the dam and experienced greater dissipation. This analysis can assist in toxic spill control and reservoir management, including field sampling and closure of water intakes.     

基于AVHRR的成都平原城市热岛效应演变趋势分析

作为城市气候主要特征之一的热岛效应有日渐明显的趋势，给城市发展和市民生活带来一系列负面影响。对2000～2006年春季下午NOAA气象卫星遥感数据的处理和分析发现，随着城市的扩张，成都平原城市热岛效应的规模呈扩大趋势。成都市区热岛强度一般为5℃-7℃，局部地方极值可达8℃以上；市中心区热岛强度相对减弱，东部工业区热岛高温区面积逐渐缩小，市区西南部热岛明显发展，致使2003年起热岛次高温区在二、三环路附近大致呈环状分布。热岛演变与近几年城市建设和改造活动密切相关。研究成果为政府相关部门缓解热岛效应、改善人居环境提供了参考依据。     

长江上游地区相对资源承载力与资源可持续利用研究——以成都市为例

采用相对资源承载力的研究思路和计算方法，计算分析了1978—2004年成都市相对自然资源承载力、相对经济资源承载力和综合承载力及其动态变化过程。研究表明：①成都市的经济资源对综合承载力的贡献大于土地资源，为成都市人口的主要承载资源；②相对经济承载力富余，但相对自然资源承载力超载；③协调经济与资源的关系、控制人口增长、保持经济适度增长是实行成都市可持续发展的关键。     

中国热带近百年气候波动与自然灾害

20世纪，中国热带气温呈波动上升趋势。在气温波动过程中有2个冷期和2个暖期。最暖的时期为80年代后，这与全球变化相一致，但是昆明最暖的时期为40年代。气候型大多为暖湿同期，这与全国其它区域的状况不同。自然灾害有加剧的趋势：台风次数增多，多台风年洪水多发，旱灾和冷害次数增多，广州曾降微雪，海口和崖县曾见霜，昆明曾有4年强降雪。     

我国西南部喀斯特地区石漠化研究进展

我国西南部喀斯特地区的石漠化是西部生态建设中面临的十分突出的地域环境问题，也是西南喀斯特地区实现可持续发展的主要障碍之一。参考国内研究的相关文献，运用比较分析法，从喀斯特石漠化的概念、分布、评价指标、生态效应、成因分析及综合治理等六方面回顾了近年来我国喀斯特地区石漠化研究的进展情况。研究结果认为，目前研究中还存在基础理论研究落后于实践活动、定量分析不足、基础数据采集工作欠缺和现有治理模式具有较大的局限性等不足，并建议从研究重点区域、探究喀斯特石漠化演变机理、在喀斯特石漠化地区开展生态综合整治工作及建设相关的信息系统等方面开展先行研究工作。     

古代黄河中游的环境变化和灾害——对都城迁移发展的影响

都城的选址、建设和迁移发展必须以环境资源为基础。我国古代的国家都城在黄河中游反复迁移，以至最后东迁南迁。在这个过程中，环境变迁和灾害一直是重要的驱动因素之一。通过统计分析历史时期洪涝和干旱灾害，以及气候水文变化资料，结合古都所在地的环境资源条件分析讨论，揭示了黄河中游环境变化和灾害对都城迁移发展的影响。都城在长安与洛阳之间的反复迁移，以及后来的东移开封，和南移到长江下游平原，环境的变迁是重要的驱动力之一。     

煤矿本质安全特征及管理方法研究

分析国内煤矿本质安全管理研究现状及存在问题,进一步讨论煤矿本质安全的内涵。探讨近年来我国煤矿事故发生的致因与根源,指出人的行为安全是我国煤矿本质安全的主要特征。通过研究我国煤矿事故的控制管理,选择事故率作为我国煤矿本质安全判别的参考标准;分析我国煤矿生产的现状与差异,提出了对我国煤矿的本质安全性进行分类判别的思想;从深入开展煤矿安全管理理论研究、加强煤矿安全管理立法、建立煤矿安全管理标准和有效组织机制等方面提出了实现煤矿本质安全的管理策略。     

国有林场安全应急管理工作的探讨

安全生产是构建和谐社会的基础和前提,国有林场的安全应急管理工作直接关系到国有林场的事业发展、经济效益和社会效益,从国有林场的实际出发,提出了一些新思路和新做法.     

袋式除尘器与电除尘器基本特性指标的对比

袋式除尘器与电除尘器是目前使用最广泛的两种粒状污染物控制设备,本文列举了两种除尘器的基本特性指标,并进行了原理、除尘效率、运行管理等方面的对比。认为袋式除尘器将成为工业粉尘控制的首选设备。