职业危害因素混合接触综合评价方法概述

作业场所同时接触多种职业危害因素的综合危害性日益引起广泛关注,如何对其进行科学的评价成为职业危害研究者面临的重要课题。本文对不同危害因素的混合危害作用的评价方法进行了系统的总结与归纳,探讨了混合作用的描述方法,分析了毒理学、流行病学、风险评价三大类方法应用于混合危害作用评价时的基本原理、核心思路和实施流程,此外对三种方法的特点进行了对比分析。     

Perceived landscape impacts of mobile telecommunications development in the Peak District National Park,England

This study explored the public perceptions of mobile telecommunications development – new landscape elements installed to deliver new technology – in a protected area. It examined: (1) the perceived landscape impacts of such development; (2) the importance attached to the socio-economic value of mobile telecommunications; and (3) the factors underlying the perceived landscape impacts of mobile telecommunications development. A postal questionnaire survey was conducted in the Peak District National Park, England with 420 respondents drawn from National Park residents and visitors, urban dwellers and members of environmental organisations. The study suggests that: (1) there was a prevailing antipathy towards the landscape impacts of mobile telecommunications development in the National Park; (2) apart from emergency uses, the other socio-economic benefits of mobile telecommunications technology were thought to be relatively unimportant in the National Park; and (3) rather than socio-demographic characteristics, it was respondents' understandings of protected areas' needs for the technology and potential health risks that had significant effects on the perceived landscape impacts. Overall, this study suggests that the significance of National Park landscapes is respected by the public, even when setalongside the convenience of modern technology, which has substantial implications for landscape planning and management in protected areas.     

厦门市大气可吸入颗粒物源解析的研究

采用2004～2005年对厦门大气中PM10开展的3期采样分析数据,利用主因子分析法定性分析厦门大气中可吸入颗粒物的主要来源,并结合多元线性回归法,求出定量的结果。分析结果表明,影响厦门市可吸入颗粒物的主要来源有四种:工业燃煤、汽车尾气、土壤风沙尘和海盐粒子,其中二次粒子为主要污染源,贡献率为30.0%,其次为汽车尾气占29.4%,土壤风沙和建筑尘的贡献约占21.7%,海洋粒子的贡献为6.5%,不可识别源18.1%。     

Relationships of nitrous oxide fluxes with water quality parameters in free water surface constructed wetlands

The effects of chemical oxygen demand (COD) concentration in the influent on nitrous oxide (N₂O) emissions, together with the relationships between N₂O and water quality parameters in free water surface constructed wetlands, were investigated with laboratoryscale systems. N₂O emission and purification performance of wastewater were very strongly dependent on COD concentration in the influent, and the total N₂O emission in the system with middle COD influent concentration was the least. The relationships between N₂O and the chemical and physical water quality variables were studied by using principal component scores in multiple linear regression analysis to predict N₂O flux. The multiple linear regression model against principal components indicated that different water parameters affected N₂O flux with different COD concentrations in the influent, but nitrate nitrogen affected N₂O flux in all systems.     

A NONLINEAR PROGRAMMING ALGORITHM FOR REAL-TIME HOURLY RESERVOIR OPERATIONS1

ABSTRACT: The optimization of real-time operations for a single reservoir system is studied. The objective is to maximize the sum of hourly power generation over a period of one day subject to constraints of hourly power schedules, daily flow requirement for water supply and other purposes, and the limitations of the facilities. The problem has a nonlinear concave objective function with nonlinear concave and linear constraints. Nonlinear Duality Theorems and Lagrangian Procedures are applied to solve the problem where the minimization of the Lagrangian is carried out by a modified gradient projection technique along with an optimal stepsize determination routine. The dimension of the problem in terms of the number of variables and constraints is reduced by eliminating the 24 continuity equations with a special implicit routine. A numerical example is presented using data provided by the Bureau of Reclamation, Sacramento, California.     

弃土场边坡稳定性和可靠性的多工况对比分析

弃土场堆积体的物理力学性质是影响弃土场边坡稳定性的关键因素.由于弃土场边坡的特殊性,其坡体物理力学指标存在明显的变异性.基于可靠性理论,考虑关键指标的不确定性,将其作为随机变量,一定程度上可克服传统边坡稳定性分析中关键参数取值难以把握的缺陷.以贵州山区平罗高速公路某弃土场边坡为例,采用Spencer法、Morgenst...     

PHYSICAL DETERMINANTS OF ECONOMIC VALUE OF RIPARIAN BUFFERS IN AN AGRICULTURAL WATERSHED1

ABSTRACT: Economic values of riparian buffers in a watershed are evaluated by the changes in the net economic return for farming with and without riparian buffers when achieving the same water quality objectives. The simulated water quality impacts of alternative farming systems using SWAT and experimental data for riparian buffers are used in a mathematical optimization model to estimate net economic return for farming subject to a water quality objective. Physical characteristics such as stream length, channel slope, average land slope, cropland percentage and several soil attributes are identified in the watershed using ARC/INFO GIS. A regression model is then used to evaluate the impacts of these physical characteristics on the estimated economic values of buffers. The study is conducted in Goodwater Creek watershed, Missouri. The results show the estimated economic value of buffers is significantly affected by some soil properties, stream length, and cropland percentage in watershed and can be used to improve the effectiveness of riparian buffers at watershed and regional levels.     

Minimizing the Cost of Keeping Options Open for Conservation in a Changing Climate

Policy documents advocate that managers should keep their options open while planning to protect coastal ecosystems from climate‐change impacts. However, the actual costs and benefits of maintaining flexibility remain largely unexplored, and alternative approaches for decision making under uncertainty may lead to better joint outcomes for conservation and other societal goals. For example, keeping options open for coastal ecosystems incurs opportunity costs for developers. We devised a decision framework that integrates these costs and benefits with probabilistic forecasts for the extent of sea‐level rise to find a balance between coastal ecosystem protection and moderate coastal development. Here, we suggest that instead of keeping their options open managers should incorporate uncertain sea‐level rise predictions into a decision‐making framework that evaluates the benefits and costs of conservation and development. In our example, based on plausible scenarios for sea‐level rise and assuming a risk‐neutral decision maker, we found that substantial development could be accommodated with negligible loss of environmental assets. Characterization of the Pareto efficiency of conservation and development outcomes provides valuable insight into the intensity of trade‐offs between development and conservation. However, additional work is required to improve understanding of the consequences of alternative spatial plans and the value judgments and risk preferences of decision makers and stakeholders. Minimizando el Costo de Mantener Opciones Abiertas para la Conservación en un Clima Cambiante     

Towards a framework for assessment and management of cumulative human impacts on marine food webs

Effective ecosystem‐based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions.