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181.
根据系统科学思想,在城市大气环境质量(AAQ)评价中,对"本质"与"异质"AAQ等量齐观,并强调污染物的低浓度长时间效应.本文探讨了两者的协同评价方法,利用常规监测资料对5个城市作了实例分析.研究结果与实际情况有较好的一致性.  相似文献   
182.
GIS在环境保护中的应用现状与发展   总被引:7,自引:2,他引:7  
结合国内外地理信息系统(GIS)在环境保护研究工作中的介入情况,阐述了GIS在环境保护领域的应用现状,并探讨了GIS在此领域应用的未来发展趋势。  相似文献   
183.
As GIS becomes an increasingly more ‘user-friendly’ tool, and more people recognize the benefits of the technology in their work environment, inevitably greater use will be made of it for a wide range of applications. The ease with which a GIS can now be used often overshadows the complexity underlying this technology and the potential difficulties that can (and do) arise when this is not fully understood. In practice, there are two routes open to the application of GIS technology for environmental studies. The first is to commission new data for the research. The second is to make use of existing data sets. Data are at the heart of any GIS application. A detailed knowledge about the data sources, the method of collection, capture, scale and sampling strategy, especially if the data are to be used in any analysis, modelling or simulation studies, is fundamental to any application. Unfortunately, information about data (metadata) is seldom available, especially for archival or legacy data sets. Furthermore, although it is now relatively easy to acquire digital data, to input, store, manipulate and display this data, and to output the results of any GIS analysis in the practical sense, little consideration is given to the problems associated with data quality and how this will ultimately affect present and future analyses and use of the output for planning and decision-making. The need to raise awareness about data quality for applications is set in the context of the development of an environmental database for the Moray Firth. Northeast Scotland, and more specifically the use of selected data sets from the database to aid in the proposed siting of an artificial reef. Using this example, this contribution explores the problems associated with the use of both existing analog and digital data sets as the basis for environmental applications, the problems of data acquisition, data quality, data standards, error and how these can affect the operational use of the data in GIS analyses. The solution to such problems appears to lie with improved error assessment and reporting. The outcome of this contribution is an attempt to offer guidance and solutions to researchers and applications specialists undertaking similar studies, by suggesting to what extent studies, such as the artificial reef siting, can safely make use of existing data sets without risking the problems associated with judgements based on inadequate information, and generated or inherent error.  相似文献   
184.
河道滞留塘系统对污染河水中氮磷的去除特性   总被引:2,自引:1,他引:2  
河道滞留塘系统是一项适用于中小型污染河流净化的生态技术,目前我国部分中小型河流污染严重,研究河道滞留塘系统对河流污染物的去除特性具有现实意义,但目前尚缺乏系统深入的研究。该研究对实际污染河水进行了一年现场试验研究,通过改变水力停留时间,考察了不同季节、不同河水水质条件下河道滞留塘系统对河水中氨氮(NH3-N)和总磷(TP)的净化效果。结果表明,河道滞留塘系统主要通过颗粒物的重力沉降作用净化河水中的总磷(TP)。在该研究条件下,TP去除率接近30%,去除速率为0.01~0.02 g.h-1.m-2。TP去除速率约为0.003倍的SS去除速率,两者间有较好的相关关系,因此可通过测定滞留塘SS去除速率来预测TP去除速率。但滞留塘系统对NH3-N无显著去除能力。  相似文献   
185.
此文论述了大弹弹体冲压工艺计算机辅助设计的主要思想和结构框架,对进一步开发弹体制造CAD/CAM技术提高了具体线索和思路。  相似文献   
186.
以滇池流域为例,介绍一种利用概化网络进行水资源调控仿真与预测的思路与方法,为流域水资源的宏观调控与管理规划提供决策支持。  相似文献   
187.
采用流动式采样与气相色谱-质谱联用法研究了意大利撒丁岛Noak’s Ark自然生态区四种主要灌木树种Juniperus phoenicea(腓尼基桧),Pistacia lentiscus(黄连木),Phillyrea angustifilia,Chamaerops humilis(欧洲矮棕)的排放速率和排放特征。结果表明,JuniPerus phoenicea(腓尼基桧),Pistacia lentiscus(黄连本),Phillyrea angustifilia主要排放萜烯类化合物,其中包括α-蒎烯、β-蒎烯、苎烯、戊花烃、莰烯、β-水芹烯、桧烯、β-香叶烯和3-蒈烯等;Chamaerops humilis(欧洲矮棕)主要排放异戊二烯。在标准条件下(温度30℃,PAR为1000μmo1.m^-2.s^-1),四种树种的排放速率分别为0.15、2.10、0.20和1.87μg/g(DW).h。  相似文献   
188.
辽宁省湿地生态环境监测指标探讨   总被引:4,自引:0,他引:4  
根据辽宁省湿地生态环境特点 ,研究讨论了建立湿地生态环境监测指标体系应遵循的原则 ,并提出了优先监测项目  相似文献   
189.
Objective: Administrative license revocation (ALR) laws, which provide that the license of a driver with a blood alcohol concentration at or over the illegal limit is subject to an immediate suspension by the state department of motor vehicles, are an example of a traffic law in which the sanction rapidly follows the offense. The power of ALR laws has been attributed to how swiftly the sanction is applied, but does the length of suspension matter? Our objectives were to (a) determine the relationship of the ALR suspension length to the prevalence of drinking drivers relative to sober drivers in fatal crashes and (b) estimate the extent to which the relationship is associated to the general deterrent effect compared to the specific deterrent effect of the law.

Methods: Data comparing the impact of ALR law implementation and ALR law suspension periods were analyzed using structural equation modeling techniques on the ratio of drinking drivers to nondrinking drivers in fatal crashes from the Fatality Analysis Reporting System (FARS).

Results: States with an ALR law with a short suspension period (1–30 days) had a significantly lower drinking driver ratio than states with no ALR law. States with a suspension period of 91–180 days had significantly lower ratios than states with shorter suspension periods, while the three states with suspension lengths of 181 days or longer had significantly lower ratios than states with shorter suspension periods.

Discussion: The implementation of any ALR law was associated with a 13.1% decrease in the drinking/nondrinking driver fatal crash ratio but only a 1.8% decrease in the intoxicated/nonintoxicated fatal crash ratio. The ALR laws and suspension lengths had a significant general deterrent effect, but no specific deterrent effect.

Practical Implications: States might want to keep (or adopt) ALR laws for their general deterrent effects and pursue alternatives for specific deterrent effects. States with short ALR suspension periods should consider lengthening them to 91 days or longer.  相似文献   
190.
The Denver Basin Aquifer System (DBAS) is a critical groundwater resource along the Colorado Front Range. Groundwater depletion has been documented over the past few decades due to the increased water use among users, presenting long‐term sustainability challenges. A spatiotemporal geostatistical analysis is used to estimate potentiometric surfaces and evaluate groundwater storage changes between 1990 and 2016 in each of the four DBAS aquifers. Several key depletion patterns and spatial water‐level changes emerge in this work. Hydraulic head changes are the largest in the west‐central side of the DBAS and have decreased in some areas by up to 180 m since 1990, while areas to the northwest show increases in hydraulic head by over 30.5 m. The Denver and Arapahoe aquifers show the largest groundwater storage losses, with the highest rates occurring in the 2000s. The results highlight uncertainty in the volumetric predictions under various storage coefficient calculations and emphasize the importance of representative aquifer characterization. The observed groundwater storage depletions are due to a combination of factors, which include population growth increasing the demand for water, variable precipitation, and drought influencing recharge, and increased groundwater pumping. The methods applied in this study are transferable to other groundwater systems and provide a framework that can help assess groundwater depletion and inform management decisions at other locations.  相似文献   
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