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951.
Fan Cheng xin 《环境科学学报(英文版)》1998,10(1):49-55
EfectsofmainrangeandstrengthfactorsonchangeofCODinashalowlakeFanChengxinNanjingInstituteofGeographyandLimnology,ChineseAcad... 相似文献
952.
The biological effects of contaminants in British estuaries and coastal waters have been studied for over 100 years. Until the 1970s. the major pollution impact on estuarine organisms was probably caused by poorly treated sewage which led to severe oxygen deficits and consequent asphyxiation of many water-breathers. However, since the introduction of improved sewage treatment in the last 30 years, a number of continuing impacts have come to light which represent true toxic effects of micro-contaminants. Sublethal changes observed in various bioassays and biomarkers are widespread in both fish and invertebrates, and in the most urbanised and industrialised estuaries, these effects are probably having impacts at the population and community levels. For example, there is good evidence to show that tributyltin from some antifouling paints has not only affected the sexuality and reproductive success of individual estuarine and coastal molluscs, but has also damaged some benthic communities of which molluscs are but a part. Although there are data to show that some contaminant concentrations are now declining, we do not yet have enough data in most cases to decide whether organisms have also begun to recover. This paper reviews the entire field of contaminant effects in UK estuarine and marine waters, focusing especially on the years 1985-2000, and makes some recommendations for future research and monitoring programmes. 相似文献
953.
1,2,4-三氯苯对3种海洋微藻的毒性效应 总被引:5,自引:1,他引:5
1,2,4-三氯苯(1,2种,4-TCB)是环境中普遍存在的持久性有机污染物之一,而1,2,4-TCB对藻类的毒性作用报道很少。以1,2,4-TCB处理后,3种海洋微藻(金藻Isochrysis Zhanjiangensis、角毛藻Platymonas Subcordiformis和扁藻Chaetoceros miielleri)的生长状况、蛋白质质量分数和叶绿素质量分数的改变来检测1,2,4-TCB对海洋微藻的毒性效应。结果表明:1,2,4-TCB对3种海洋微藻的生长均有一定的抑制作用,该效应表现出一定的浓度和时间依赖性;1,2,4-TCB处理4d后,3种海洋微藻细胞蛋白质质量分数和叶绿素质量分数下降,呈现一定的浓度—效应关系,这表明1,2,4-TCB对3种海洋微藻产生毒害效应,其作用机制可能与藻类光合作用功能降低和蛋白质功能受损有关。1,2,4-TCB在一定程度上降低了藻类饵料的利用价值,而且对食物链下游生物具有潜在的危害性。 相似文献
954.
Elise D. Ferree 《Behavioral ecology and sociobiology》2007,62(1):109-117
Theory, empirical examples, and recently, proximate mechanisms point to the possibility of adaptive sex ratio adjustment in
various organisms. General predictions state that a female should adjust her offspring sex ratio to maximize the benefits
or minimize the costs of reproduction given her physical condition or current social and environmental conditions. I tested
for an influence of male attractiveness on brood sex ratio in a population of dark-eyed juncos (Junco hyemalis thurberi) by manipulating a male’s white outer tail feathers (“tail white”). Experimentally increasing male tail white did not significantly
affect sex ratio, nor was premanipulated male tail white significantly related to brood sex ratio. However, the amount of
white on the female’s outer tail feathers, independently of female condition, was positively related to the number of sons
in a brood. Determining how a female’s potential genetic contribution to her sons’ attractiveness influences offspring sex
ratio should be a priority for future research. 相似文献
955.
Evaluation of CFD Simulation using RANS Turbulence Models for Building Effects on Pollutant Dispersion 总被引:5,自引:0,他引:5
CFD evaluations were performed to examine the applicability of the RANS methods in simulating pollutant dispersion near, within
and over three typical building configurations: (1) an isolated building, (2) a building array and (3) an urban intersection.
The CFD results are compared with values obtained from wind tunnel tests. In some situations major differences between the
wind tunnel tests and the CFD results were observed. The main source of difference between the CFD and wind tunnel results
was inadequate modelling of local flow patterns using the RANS turbulence models. Also inappropriate evaluation of high intermittent
turbulent mixing in the RANS approach may lead to either over-prediction or under-prediction of the concentration level, by
up to a factor of 10, depending on the case investigated. 相似文献
956.
We analyze data from a complex repeated measures experiment directed at the evaluation of the response to an electric stimulus
applied to mussel nerves under 5 different salinity levels. We discuss the form of the relation between the response and the
different salinity levels, as well as the choice of an adequate within subjects covariance structure that includes random
effects and autoregressive models. 相似文献
957.
Cost-effective environmental policy generally requires that all emission sources are faced with the same tax. In this paper I discuss how the existence of induced technological change may alter this result, if at least some of the effect is external to the firm. Focusing on Learning by doing (LBD) effects in abatement activities, it is shown that emission sources with external learning effects should be faced with a higher tax than emission sources with only autonomous technological change. By using simple numerical simulations, it is further investigated to what degree a cost-effective climate policy differs from a free quota market, under various assumptions about learning effects, diffusion of technology and environmental targets. The results indicate that optimal taxes may be significantly higher in the industrial world than in the developing world. Moreover, the industrial world's share of global abatement may be much higher in a cost-effective solution than in a free quota market. The global cost savings of a fully flexible implementation of the Kyoto Protocol are further questioned, as potential spillover effects of technological growth in the industrial world are not internalised in the market. 相似文献
958.
Efficient statistical mapping of avian count data 总被引:3,自引:0,他引:3
J.?Andrew?RoyleEmail author Christopher?K.?Wikle 《Environmental and Ecological Statistics》2005,12(2):225-243
We develop a spatial modeling framework for count data that is efficient to implement in high-dimensional prediction problems. We consider spectral parameterizations for the spatially varying mean of a Poisson model. The spectral parameterization of the spatial process is very computationally efficient, enabling effective estimation and prediction in large problems using Markov chain Monte Carlo techniques. We apply this model to creating avian relative abundance maps from North American Breeding Bird Survey (BBS) data. Variation in the ability of observers to count birds is modeled as spatially independent noise, resulting in over-dispersion relative to the Poisson assumption. This approach represents an improvement over existing approaches used for spatial modeling of BBS data which are either inefficient for continental scale modeling and prediction or fail to accommodate important distributional features of count data thus leading to inaccurate accounting of prediction uncertainty. 相似文献
959.
960.
Standard laboratory toxicity tests assess the physiological responses of individual organisms to exposure to toxic substances under controlled conditions. Time and space restrictions often prevent the assessment of population-level responses to a toxic substance. Contaminants can affect various biological functions (e.g. growth, fecundity or behavior), which may alter different demographic traits, leading to population-level impacts. In this study, immune suppression, reproductive dysfunction and somatic growth impairment were examined using life history matrix models for coho salmon (Oncorhynchus kisutch), sockeye salmon (Oncorhynchus nerka) and chinook salmon (Oncorhynchus tshawytscha). Our intent was to gauge the relative magnitude of response to toxic effects among species and between life history stages, not provide a specific estimate of population growth rate or abundance. Effects due to immune suppression were modeled as reductions in age-specific survival. Toxic impacts on reproductive function were modeled as a 10% reduction in reproductive contribution for all reproductively mature age groups. Model runs that examined the effect of somatic growth reduction on population parameters incorporated both survival and reproductive impacts. All impacts were modeled as 10% reductions in the affected population demographic parameters. First-year survival and reproductive impacts produced similar population growth rates (λ), but resulted in different sensitivity and stable age distributions. Modeled somatic growth reduction produced additive effects on survival and reproduction. Toxic stressors producing similar changes in λ did not necessarily produce similar changes in the age distributions. Sensitivity and elasticity analyses demonstrated that changes to the first-year survival rate produced the greatest per-unit effect on λ for each species. Alteration in abundance of mature females also strongly influenced λ. Differences observed between species showed that the number of reproductive ages and time to reproductive maturity were important components for population-level responses. These results emphasize the importance of linking toxicity responses at low concentrations to the demographic traits they affect, and help to highlight the toxicity tests that are more suitable for assessing impacts on the focal species. Additionally, life history modeling is a useful tool for developing testable hypotheses regarding impacts on specific populations as well as for conducting comparisons between populations. 相似文献