北京山区典型流域不同海拔椴树种群的空间点格局分析

采用点格局分析法对不同海拔的椴树(Tilia miqueliana Maxim.)种群进行分布格局及其种间关系进行了研究。结果表明:整体上群落内以中龄树个体数为最多,小树次之,成年树个体最少。随着海拔的增加可以看出:小树(d≤5 cm)随着海拔的增加而减少,中树(5 cm20 cm)的规律不明显;椴树种群的空间分布格局与空间尺度(25 m内)有密切关系,在较小的空间尺度上倾向于非随机分布,具有明显的空间相关性;在>15 m或25m的某临界尺度时却倾向于随机分布,同时空间关联变得微弱。随着海拔的增加,各物种聚集分布的尺度有逐渐减小的趋势。种间关系随着海拔的增加,物种间的正相关尺度有增加的趋势。     

我国环境立法的误区及对策研究

我国目前的环境立法存在一些不足,有些具有“部门立法”、“主体立法”的特征,对行政管理相对人而言又多表现为“义务本位”立法;某些法律与另一些法律之间存在着矛盾,一些法律制度和措施还不够完善。要改变这种状况,环境立法工作应当实现以下几点转变:一是政府部门应由“权力主体”向“义务主体”转变,二是由“主体立法” 向“行为立法”转变,三是行政管理相对人由“义务本位”向“权利义务一致”转变,四是环境法律制度应由行政性制度向经济性制度转变,五是在立法技术上由强调速度和数量向强调质量转变。     

Environmental equity and the distribution of toxic release inventory and other environmentally undesirable sites in metropolitan New York City

We study the question of environmental equity via generalized linear modeling for the metropolitan New York City region and ask whether, after accounting for socioeconomic status, particular racial/ethnic populations bear a disproportionate burden of hosting environmentally undesirable sites. Our data consist of population demographics for 2216 census tracts linked to 354 environmentally undesirable facilities, including toxic release inventory sites, hazardous waste treatment, storage, and disposal facilities, and other common urban problem sites such as landfills, incinerators, bus garages and sewage treatment plants. Using generalized linear and additive modeling techniques, we find that racial/ethnic demographics, in particular the Hispanic percentage of a tract's population, are significantly associated with the presence of potentially environmentally adverse sites. This leads us to the conclusion that, over the whole metropolitan New York City area, the Hispanic population is proximate to more sites than other populations. At the same time, we find that both Hispanics and African-Americans are more proximate to these sites in the Bronx and Queens. However, we also find indications that Hispanics and African-Americans are less likely to be proximate to the sites in Manhattan. We establish an empirical relationship that warrants additional study in order to establish the causes for the population distribution and whether a basis for a claim of discrimination exists.     

Reducing Nitrogen Export from the Corn Belt to the Gulf of Mexico: Agricultural Strategies for Remediating Hypoxia

SPAtially Referenced Regression on Watershed models developed for the Upper Midwest were used to help evaluate the nitrogen‐load reductions likely to be achieved by a variety of agricultural conservation practices in the Upper Mississippi‐Ohio River Basin (UMORB) and to compare these reductions to the 45% nitrogen‐load reduction proposed to remediate hypoxia in the Gulf of Mexico (GoM). Our results indicate that nitrogen‐management practices (improved fertilizer management and cover crops) fall short of achieving this goal, even if adopted on all cropland in the region. The goal of a 45% decrease in loads to the GoM can only be achieved through the coupling of nitrogen‐management practices with innovative nitrogen‐removal practices such as tile‐drainage treatment wetlands, drainage–ditch enhancements, stream‐channel restoration, and floodplain reconnection. Combining nitrogen‐management practices with nitrogen‐removal practices can dramatically reduce nutrient export from agricultural landscapes while minimizing impacts to agricultural production. With this approach, it may be possible to meet the 45% nutrient reduction goal while converting less than 1% of cropland in the UMORB to nitrogen‐removal practices. Conservationists, policy makers, and agricultural producers seeking a workable strategy to reduce nitrogen export from the Corn Belt will need to consider a combination of nitrogen‐management practices at the field scale and diverse nitrogen‐removal practices at the landscape scale.     

通信机房热环境下接续性电磁辐射点信息检测研究

提出一种改进双耦合Duffing系统自适应检测方法,并利用改进的滤波器对放大后电磁辐射点信号进行自适应滤波处理,消除信号中噪声干扰,降低电磁辐射点中含有的噪声,在此基础上,在双耦合Duffing系统中引入信号变尺度处理和自适应调整驱动力幅值的方法,实现通信机房热环境下接续性电磁辐射点信息检测.实验结果表明,所提方法能够有效抑制接续性电磁辐射点信号噪声,保证接续性电磁辐射点信息检测的准确性和完整性.     

两种空气自动监测系统的比较

国产长光程空气自动监测系统是中国自行研制的更为先进、更具自动化的系统，24h点式仪器是老式空气检测仪器，对这两种新、老仪器的比较可以看出在运行过程中的利弊。     

甘肃不同台站地磁垂直分量变化特征分析

本文应用甘肃省嘉峪关、兰州、天水地磁台2003--2006年4年地磁垂直分量Z的资料分析了静日S。日变形态、日变幅度以及日变形态畸变的变化特征。结果显示，不同台站日变形态基本相似；包含在日变形态畸变现象的低点位移和拉平现象具有明显的季节性变化规律，其在地磁冬季出现的概率远远高于其他季节，与日变幅变化关系密切。     

不同季节生态型大白菜光合作用对夏季高温强光的响应

分别以春季品种强势、夏季品种夏珍白1号和秋季品种鲁白8号大白菜（Brassica campestrisL.ssp.Pekinesis(Lour)Olsson）为试材，研究了不同季节生态型大白菜在莲座末期或结球初期，叶片光合作用对夏季高温、强光胁迫的响应。结果表明，不同季节生态型大白菜在高温、强光下的光合特性存在明显差异，夏珍白1号的光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）的极值明显高于强势和鲁白8号，光合“午休“现象较轻；中午12：00时光系统Ⅱ的光化学效率（Fv/Fm）夏珍白1号、强势较高，鲁白8号较低；室内人工控制高温、强光下，夏珍白1号的光合速率较高，鲁白8号较低；利用直线方程求得大白菜的温度补偿点为55℃左右，品种略有差异，夏珍白1号（56.97℃）高于强势（54.81℃）和鲁白8号（54.40℃）。图5参13。     

STATISTICAL IDENTIFICATION OF STORAGE MODELS WITH APPLICATION TO STOCHASTIC HYDROLOGY1

ABSTRACT: This paper describes a method for the statistical identification of storage models for daily riverflow time series, together with numerical results. The first step in the identification process is to obtain a discrete time version of a storage model using a local linearization approach. It is shown that the discrete time version thus obtained may be utilized in the identification of the original storage model. A statistical method for the identification of daily rainfall time series models used in simulation is also presented. This identification procedure employs the maximum likelihood method for point process data analysis and is illustrated by means of numerical examples.     

An overview of short‐term tests for the mutagenic and carcinogenic potential of pesticides

Abstract

In the last few years, marked progress has been made in the development of methods for evaluating the mutagenic and carcinogenic potential of pesticide chemicals. The correlation of genetic and related biological activity in short‐term tests with carcinogenic activity in whole animals allows the utilization of short‐term mutagenicity bioassays to prescreen chemicals for effects related to mutation induction and presumptive carcinogenicity. In addition, bioassays now available can measure directly the chemical transformation of normal cells in culture into cells capable of producing tumors when injected into animals.

This paper will review briefly the major types of relevant short‐term tests and will develop a rationale for a phased approach to the evaluation of the mutagenic and carcinogenic potential of environmental chemicals. This approach involves the sequential application of bioassays which are organized into a three‐level matrix emphasizing first detection, then confirmation, and finally hazard assessment. Chemicals demonstrating positive results in the short‐term detection systems and confirmatory bioassays are pursued in higher level whole animal tests. A core battery of tests is proposed to operationally define a negative result. The phased approach should facilitate a cost effective utilization of limited testing resources and provide protection for human health in proportion to the anticipated hazard.

Results obtained in evaluating a series of thirty‐eight pesticide chemicals according to the phased approach are discussed in detail.