Assessment and management of urbanization-induced ecological risks

The urban ecological risk incurred during the processes of urbanization has been constantly accumulating, creating a severe challenge for China to achieve sustainable urban development. At present, research on systematic evaluation of urban ecological risks is still inadequate, especially at an urban ecosystem level. In this special issue, we use Xiamen City as an example to identify the sources and receptors of urban ecological risks, to develop a methodology system of urban ecological risk assessment, and to propose a method for the management of urban ecological risks. This special issue contains 11 research articles resulting from a comprehensive research project funded by China’s National Natural Science Foundation. The innovations reported in this special issue include a framework of urban ecological risk assessment and a standardized procedure for carrying out urban ecological risk assessment using multiple stressors and endpoints.     

Potentially toxic metal contamination of urban soils and roadside dust in Shanghai, China

A detailed investigation was conducted to understand the contamination characteristics of a selected set of potentially toxic metals in Shanghai. The amount of Pb, Zn, Cu, Cr, Cd and Ni were determined from 273 soil/dust samples collected within urban area. The results indicated that concentration of all metals except Ni in soils was significant, and metal pollution was even severer in roadside dust. A series of metal spatial distribution maps were created through geostatistical analysis, and the pollution hotspots tended to associate with city core area, major road junctions, and the regions close to industrial zones. In attempt of identifying the source of metals through geostatistical and multivariate statistical analyses, it was concluded as follows: Pb, Zn and Cu mainly originated from traffic contaminants; soil Ni was associated with natural concentration; Cd largely came from point-sourced industrial pollution; and Cr, Ni in dust were mainly related to atmospheric deposition.     

Rural landscape planning case study of Nanhua State Farm

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渤海莱州湾沉积物-水界面溶解无机氮的扩散通量

为了解不同条件下沉积物中有机物对水体无机氮的贡献,采用野外采样和现场培养法,在１９９７－０５和１９９７－０７莱州湾２个航次进行了沉积物－水界面营养盐扩散通量的实验研究,ＮＯ－３和ＮＨ＋４的扩散通量分别为０．０３８—３．６５ｍｍｏｌ／（ｍ２·ｄ）和０．９６—２．５２ｍｍｏｌ／（ｍ２·ｄ）．培养结果说明充氮或充空气与加氯化汞或不加氯化汞对沉积物－水界面溶解无机氮的扩散通量没有明显影响．莱州湾底部营养盐的扩散通量与其它地区比较处于中等偏上水平．     

城市交通机动车污染控制研究进展

城市交通机动车污染问题非常复杂，在许多不可控因素，城市交通是一个动态系统，污染物排放量始终处于变化之中，控制城市交通污染，必须严格控制机动车排放，该文介绍了国内外对城市机动车污染控制研究的概况，以及几种城市中污染物扩散的模型，展望了这方面研究前发展趋势，并提出了可持续发展的效能系统设计与管理的新概念。     

城市垃圾污染防治对策探讨

从城市拉圾产生的机制入手，分析了城市垃圾污染产生的原因，并对目前所采取的主要处理方法人季简要评述，在此基础提出了实现城市垃圾最小量化，推动垃圾资源化产业、提高垃圾无害化处理水平，中化监督管理等几点城市垃圾污染防治的对策。     

城市高架道路建设对机动车尾气污染的影响分析

通过现场观测和对比，分析了城市一般道路上和城市高架道路下机动车排放污染物浓度差异的原因，分析结果表明，扩散条件对城市机动车尾气污染有着重要影响，例举日本对城市高架道路建设的有关规定，提出应重视城市高架道路建设的环境预评估等。     

农村劳动力区域流动基本特点研究

给出了农村劳动力流出、流入率的定义,计算了全国各省（市、区）的劳动力流出、流入率,分析了农村劳动力流出、流入率分布的三大特征,论证了农村劳动力流动的３个基本条件,即经济、文化和旅行能力。进一步阐述了农村劳动力流出率分布的基本特征,基于这些分析给出了政策性建议     

生物多样性与城市景观生态建设

论述了生物多样性在城市景观中的重要作用，生物多样的现代城市中的衰落以及城市生物多样性保护与景观生态建设的关系，提出应将生物多样性保护计划同城市景观生态建设结合起来。     

Growth in urban extent and allometric analysis of West African cities

Urban area expansion is happening at much faster rates in Asian and African cities than elsewhere in the world. This study uses multi-temporal Landsat images to map the urban extent of six small to large cities in West Africa at four different time steps from the early 1970s–2010. The selected cities are Kumasi of Ghana, Daloa of Cote d’Ivoire, Abuja and Kano in Nigeria, Kindia of Guinea, and Ouagadougou of Burkina Faso. All cities revealed significant urban growth in both urban area and population; however, it was apparent that there was a lot of variability in urban area development. Exponential urban growth rates in the cities were measured as ranging between 0.026 and 0.077, with allometric scaling factors matching those of other countries.