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Water quality in rural areas of the Czech Republic: Key study Slapanka River catchment 总被引：1，自引：0，他引：1
The article evaluates the water quality in rural areas in the Czech part of Labe River catchment using the example of Slapanka River catchment. This river drains a typical landscape of Ceskomoravska Highland. Water quality in rural areas is still very low and the attention is paid to organic substances and nutrients. Increased amount of them in streams is caused mainly by agriculture and production of municipal wastewater resulting in increased eutrophication. A significant part of the article consists in the evaluation of point and non-point sources of water pollution. Identifying the type of the pollution source is helped by regression analysis using data from the public monitoring network. Eleven sampling sites were selected for evaluating the water quality. Physical and chemical analyses were made 12 times during the field monitoring in the years 2001–2003.In long-term development water quality has improved in all monitored parameters during the last 15 years. Least significant improvement has been found with the concentration of nitrate nitrogen. The water quality within the whole catchment area still remains low.To reduce the influence of pollution sources, we recommend the sanitation of diffuse sources of pollution from small settlements with less than 2000 inhabitants, and a successive change from agricultural management and intensive mass production to extensive ways, especially in mountain and sub-mountain areas. 相似文献
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资源学、环境学与经济学是相对独立的学科，但它们之间又具有密切的内部联系。资源（自然资源）、经济和环境是现代社会发展中的三个重要方面。本文试图用综合发展的观点，分析资源、环境、经济三者之间的相互矛盾、相互依赖、相互影响、相互作用的规律，论述处理好资源、环境与经济相互协调、发展的关系。这也是社会经济可持续发展的时代要求。 相似文献
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This paper describes several factors which control the magnitude of Reserves-to-Production (R/P) ratio, the necessity of preliminary analysis of them and the proper interpretation of this ratio, as it applies to different conditions and countries. It also describes the importance to characterize the ability of reserves to provide the increased oil production (or keeping its level stable) and consider it a main criterion of its quality and sufficiency. The deterioration in the quality of reserves because a definite point of the exploratory degree of the petroliferous basins and during the oil-field production period is a permanent factor, which has to be taken into account. All else aside it leads to the formal increase of the R/P ratio without an ability for production growth. The careful analysis of probable and possible reserves can help determine successful ways for replenishment of the proved reserves and increased oil production. 相似文献
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This paper explores variant space-time models for log-transformed West Nile virus (WNv) mosquito data, which explicitly account for both local environmental conditions and complex dependent structures. Four space-time models take various forms to accommodate correlated structure in space and time, nested data, and nonstationarity. The average WNv mosquito abundance is captured by a global trend across all four models, but different model assumptions are imposed on the stochastic component of the proposed models: a simple multivariate linear regression model with independent and identical errors, a site-specific linear mixed model with temporally correlated errors, a week-specific linear mixed model with spatially correlated errors, and a local space-time kriging model. In a case study, the predictive performance of the four models was assessed using data collected in 2007 and 2008 for the Greater Toronto Area by the mosquito surveillance program of Ontario Ministry of Health and Long-term Care: the local space-time kriging model outperforms others, but closely followed by a site-specific linear mixed model with temporal correlation. Our findings suggest that the predictive accuracy of space-time WNv mosquito abundance models can be enhanced by explicitly taking into account spatiotemporal correlation, nonstationarity, and the data collection procedure, such as surveillance design, based on sound understanding of mosquito behavior and population dynamics. 相似文献
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选取2011年1月~2012年12月上海台网数据库中记录的37次ML≥2.0地震的数字地震波资料,利用单次散射的Aki模型,计算上海及邻区尾波Q值,拟合Q值对频率的依赖关系,结果为Q(f)=(176.2±87.26)·f0.898 4±0.290 8。与国内其他区域相比,本区域Q值偏大,对频率依赖性低。结合上海及邻区地质特征及同期小震空间分布特点,将研究区域划分为以下4个小震密集区:苏中沿海区域、南黄海区域、苏州—东海区域、宁波—舟山区域,分区进行Q值统计分析,表明尾波Q值数据能够较好地反映该区域地震活动性。 相似文献
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A key factor for computing environmental contours is the appropriate modeling of the dependence structure among the environmental variables. It is known that all the information on the dependence structure of a set of random variables is contained in the copulas that define their multivariate probability distribution. Provided that copula parameters are estimated by means of statistical inference using observations, recordings, numerical or historical data, uncertainty is unavoidably introduced in their estimates. Parametric uncertainty in the copulas parameters then introduces uncertainty in the environmental contours. This study deals with the assessment of uncertainty in environmental contours due to parametric uncertainty in the copula models that define the dependence structure of the environmental variables. A point estimation approach is adopted to estimate the statistics of the uncertain coordinates of the environmental contours considering they are given in terms of inverse functions of conditional copulas. A case study is reported using copulas models estimated from storm hindcast data for the Gulf of Mexico. Uncertainty in environmental contours of significant wave height, peak period and wind speed is assessed. The accuracy of the point estimation of the mean and variance of the contour coordinates is validated based on Monte Carlo simulations. A parametric study shows the manner in which greater parametric uncertainty induces larger variability in the environmental contours. The influence of parametric uncertainty for different degrees of association is also analyzed. The results indicate that variability between contours considering parametric uncertainty can be meaningful. 相似文献
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赤潮预报的人工神经网络方法 总被引：2，自引：0，他引：2
基于渤海湾赤潮观测数据(2003年5月~9月),对藻类浓度与环境因子进行了相关性分析,选择出影响藻类浓度的主要环境因子,然后对主要环境因子作主成分分析,在主成分分析的基础上,建立了一个用于赤潮预报的人工神经网络模型。 相似文献
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The effect of the Prandtl number on convection in a planar three-dimensional geometry is investigated in this study. We have employed a numerical scheme to integrate the governing equations. Differently from previous studies we have chosen stress-free boundaries. Experiments have been performed at a Rayleigh number of Ra = 10 6 for Prandtl numbers (Pr) ranging from 0.025 to 100. We have further conducted one experiment in the limiting case of infinite Prandtl number. Despite the differences in the geometry and the boundary conditions, as compared to other studies, we find a similar transition in the dynamics of the flow when the Prandtl number is increased. While the velocity and the temperature structure show diffusive character at low Pr, sharp thermal boundary layers form at high Pr. The heat transport efficiency increases with Pr until a transition value is reached, from there on Nu behaves almost asymptotically. The transition can not be caused by a change in hierarchies between velocity and thermal boundary layers, as suggested in other studies. Due to the stress-free boundaries, a velocity boundary layer does not exist. We observe that the toroidal part of the flow is strong at low Pr and looses its strength with increasing Pr, thus it is likely to be responsible for the transition. In a further chapter we demonstrate that due to the neglect of the toroidal part in two-dimensional calculations at low Pr results are obtained which are misleading, even in a qualitative sense. Infinite Pr results from 2D calculations closely resemble the dynamics of fully 3D flows. 相似文献
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