FECAL‐INDICATOR BACTERIA IN STREAMS ALONG A GRADIENT OF RESIDENTIAL DEVELOPMENT1

ABSTRACT: Fecal‐indicator bacteria were sampled at 14 stream sites in Anchorage, Alaska, USA, as part of a study to determine the effects of urbanization on water quality. Population density in the subbasins sampled ranged from zero to 1,750 persons per square kilometer. Higher concentrations of fecal‐coliform, E. coli, and enterococci bacteria were measured at the most urbanized sites. Although fecal‐indicator bacteria concentrations were higher in summer than in winter, seasonal differences in bacteria concentrations generally were not significant. Areas served by sewer systems had significantly higher fecal‐indicator bacteria concentrations than did areas served by septic systems. The areas served by sewer systems also had storm drains that discharged directly to the streams, whereas storm sewers were not present in the areas served by septic systems. Fecal‐indicator bacteria concentrations were highly variable over a two‐day period of stable streamflow, which may have implications for testing of compliance to water‐quality standards.     

Dynamic modeling of chemical fate and transport in multimedia environments at watershed scale-I: theoretical considerations and model implementation

A geo-referenced environmental fate model was developed for analyzing unsteady-state dispersion and distribution of chemicals in multimedia environmental systems. Chemical transport processes were formulated in seven environmental compartments of air, canopy, surface soil, root-zone soil, vadose-zone soil, surface water, and sediment. The model assumed that the compartments were completely mixed and chemical equilibrium was established instantaneously between the sub-compartments within each compartment. A fugacity approach was utilized to formulate the mechanisms of diffusion, advection, physical interfacial transport, and transformation reactions. The governing equations of chemical mass balances in the environmental compartments were solved simultaneously to reflect the interactions between the compartments. A geographic information system (GIS) database and geospatial analysis were integrated into the chemical transport simulation to provide spatially explicit estimations of model parameters at watershed scale. Temporal variations of the environmental properties and source emissions were also considered in the parameter estimations. The outputs of the model included time-dependent chemical concentrations in each compartment and its sub-compartments, and inter-media mass fluxes between adjacent compartments at daily time steps.     

人口、资源与环境经济学教材比较研究

人口、资源与环境经济学是理论经济学下设立的一个二级学科。自1997年设立以来，很多学者对其学科体系进行了探索。出版了一些著作和教材。本文以现代课程与教学论的观点为指导．采用文献研究、比较分析、统计分析的方法．从教材现状、体系结构、内容、表现形式和手段等方面对国内外人口、资源与环境经济学教材进行了详细的比较研究，并在此基础上为新教材建设提出了建议。以期为国内相关教材的改进和完善提供参考依据。这些建议是：统一并完善教材体系；理论要联系实际．培养学生学习兴趣和解决实际问题能力；注重学科领域最新成果的运用。增强教材的时代性和科学性；注重表现形式和手段多样性，帮助读者理解抽象的经济理论。     

大修安全管理基本原则初探

根据大修安全管理的特点,提出了搞好大修安全管理应遵循的基本原则,并用科学观点进行了详细论述。     

五台山亚高山草甸小格局分析

用种毗连法和种小区法对五台山２４００２８００ｍ的亚高山草甸的小格局分析．结果表明：在小格局中，大部分种与优势种苔草呈正关联；小格局规模都较小，各个种趋于交错分布；不同规模的格局应用不同的分析方法，小格局不能用中格局分析方法进行研究；种小区法和种毗连法都是有效的小格局分析方法，从本文结果看前者优于后者．     

Long-term population dynamics of ixodid ticks and development of tick-borne encephalitis foci under conditions of the middle taiga subzone

Long-term (1995–2003) population dynamics of ixodid ticks and their main hosts (small mammals) and conditions providing for the formation of tick-borne encephalitis (TBE) foci were studies in the middle taiga subzone (Karelia). The results show that the bank vole (Clethrionomys glareolus Schr.) is the main host for the larvae and nymphs of Ixodes persulcatus Schulze, 1930 and for the larvae, nymphs, and adult individuals of I. trianguliceps Birula, 1895. The proportion of ticks feeding on this species (relative to their total number) reaches 63.3% (64.0% of I. persulcatus and 61.1% of I. trianguliceps). Activity of a TBE focus is determined primarily by the abundance of bank voles of older age groups.     

城市化发展过程的非线性模拟

模拟城市化发展过程方法提取城市化发展中的人口和经济两个主要因子。根据其相互制约的关系。运用非线性理论构筑城市化发展的非线性模型。并采用定性和定量相结合的方法。进行数值模拟，并构建这一模型。解释城市化发展过程中的部分现象。这一模型是理想状态下实现的。无法取得现实中准确的数值，仍需加以修正才能更精确的模拟城市化发展的现实过程。     

On Population Mobility in Market Economy

A general survey of the changing process of economic development of human society indicates three historical development stages: agricultural-oriented natural economy, industrial-oriented market economy and knowledge- oriented market economy. In the first natural economic era, the most important factor of production is the land and the land resource is the first resource in the economic era of agriculture. In the market economy era of industry, capital, especially material and monetary capital…     

Response of Bird Populations to Farmland Set-Aside Programs

Abstract:  The role of agricultural landscapes in biodiversity conservation has been largely ignored despite their potential role in conserving declining species. Within agricultural landscapes, set-aside programs may offer the most promising conservation opportunities due to the large area involved in these programs. I explored the relationship between set-aside effect size—on the basis of data from field studies of birds in cropland and set-aside fields—and population changes following establishment of these fields. Species whose abundance was most strongly influenced by the establishment of set-aside lands also tended to show positive changes in population trends following broad-scale implementation of the set-aside program. This relationship was strongest for grassland obligate birds, a group of birds experiencing broad-scale population declines throughout North America. There is now increasing evidence that set-aside lands within the United States are providing population-level benefits to grassland birds. Nevertheless, there are also increasing concerns about the stability of these set-aside lands in the face of increased demand for crops and rising commodity prices. If set-aside area within the United States is allowed to decline, additional declines of birds and perhaps other taxa within agricultural landscapes seem likely.