城市用地扩张、规模经济与经济增长质量

城市用地扩张不仅影响经济增长数量,还通过产业结构升级、城市化、生态环境变化和规模经济等路径影响区域经济增长质量。城市用地扩张,促进市场范围扩大,有利于区域内与区域间开展分工合作,提升城市的集聚经济效益与规模经济水平;但若城市用地扩张使区域突破最优规模经济状态后,因管理与服务成本、交通成本和环境成本等快速增加,城市规模效率会下降,对经济增长质量产生负影响。实证研究结果表明:在全国、中部和西部地区3个空间维度,城市用地扩张与规模效率间存在倒U型关系,而在东部地区此关系并不成立;在4个空间维度,城市用地扩张通过规模经济路径对全要素生产率的影响都为负,表明城市用地扩张已使各区域突破最优规模经济状态,土地要素投入存在冗余现象,与资本、劳动等要素配置比例非最优。研究结果还表明,人力资本、城市化、产业结构升级、基础设施等变量对经济增长质量有正影响。     

徐州市不同功能区重金属污染与健康风险评价

为了解徐州市不同功能区表层土壤重金属的污染特征和健康风险,采集了65种城市表层土壤样品,分析Cr、Ni、Cu、Zn、Cd、Pb等6种重金属的元素含量与富集特征。结果发现除绿地区Cr以外,3个区域的6种重金属元素均出现了不同程度的富集。采用《污染场地风险评估技术导则》推荐的健康风险模型对3个功能区进行健康风险评价,结果表明:Cr、Ni、Cu、Zn、Cd等5种重金属的非致癌风险呈现居民区>交通区>绿地区的趋势;经口摄入和呼吸吸入的健康风险大于皮肤接触;居民区Cr的健康风险为2.21,需要进行土壤治理;当空气铅含量为0.38μg/m3时,3个区域0~7岁儿童血铅浓度在10.0~17.0μg/L。     

北京市城市河流中精神活性物质的污染水平及环境风险

为评价北京市城市河流地表水体中5种精神活性物质〔METH(甲基苯丙胺)、AMP(苯丙胺)、KET(氯胺酮)、EPH(麻黄碱)和HA(羟亚胺)〕的环境风险,通过对固相萃取柱(Oasis HLB、Oasis MCX、Oasis WAX和Oasis PRiME HLB)类型、水样酸化、洗脱剂类型及体积等条件的确定,建立了同时测定水环境中精神活性物质的固相萃取-液相色谱-质谱(SPE-LC-MS/MS)联用方法,并对北京市城市河流地表水体中5种精神活性物质的质量浓度水平进行了调查,采用RQ(风险熵)法进行了风险评价. 结果表明,在水样未酸化条件下,Oasis MCX柱对精神活性物质的回收率最高,使用含5%(V/V)氨水的甲醇作为洗脱液,5种精神活性物质的回收率可以达到81.8%~91.1%. 地表水水体基质加标结果表明,5种精神活性物质的加标回收率均大于75.5%,相对标准偏差均小于10.0%. 方法检出限为0.30~0.80 ng/L,定量限为1.00~2.68 ng/L. 北京市7条城市河流中5种精神活性物质的质量浓度在1.00~99.51 ng/L之间. EPH在所有采样点均被检出且质量浓度较高,ρ(EPH)平均值为22.79 ng/L;ρ(AMP)相对较低,在1.54~11.23 ng/L之间,但AMP检出率为97.06%;ρ(METH)较高,平均值为14.63 ng/L,最高值(99.51 ng/L)出现在坝河. 研究显示,北京市地表水中5种精神活性物质的RQ均小于0.1,表明其可能的环境风险较低,但由于精神活性物质本身具有生物活性,它们对城市河流水生生态系统产生的潜在危害不容忽视.      

闽江福州段与城市内河表层沉积物重金属污染特征研究

为了探讨城市内河对闽江福州段重金属污染的影响特征,本文对闽江福州段和福州城市主要内河表层沉积物中的Cr、Ni、Cu、Zn、As和Pb 6种重金属元素进行了系统的分析,并采用地累积指数法和潜在生态风险评价法进行污染情况和潜在危险评估.研究结果表明,表层沉积物中重金属Cr、Ni、Cu、Zn、As和Pb含量范围分别为:5.55~131.35、0.74~138.82、2.45~95.84、24.24~609.72、2.82~95.90、13.91~108.45mg·kg~(-1),各重金属含量平均值明显高于福建省土壤环境背景值,但低于国家土壤环境质量Ⅱ类标准值(除As略高于Ⅱ类标准).地累积指数法评价结果表明,表层沉积物中重金属大多为无污染或中污染程度,受人类活动影响强烈.潜在生态风险评价法表明,表层沉积物中重金属Cr、Ni、Cu、Pb和Zn存在轻微潜在风险,As以中等潜在风险为主,总体存在轻微潜在风险.重金属污染物的空间分布与福州市的发展格局相适应,人类活动集中的老城区和工业密集区,是闽江与内河重金属污染物含量相对较高的区域.城市内河汇入闽江后,携带的大量重金属污染物加剧了闽江重金属污染.建议加强对闽江重金属含量较高的晋安河段、光明港段-磨溪河段的污水排放监控.     

A Street Categorization Method to Study Urban Noise: The Valladolid (Spain) Study

Abstract We describe the application of a categorization method for road traffic noise (TN) evaluation. The method assumes that urban noise is stratified according to a five-category classification of streets based only on their use as communication routes. The method has previously been shown to be valid for towns under 220,000 inhabitants, and in the present case is applied to study the urban noise in Valladolid (Spain), a town with a population of nearly 320,000 inhabitants. Novel mathematical tools in this field are used to analyze the method. We demonstrate the existence of a stratification of the streets sound levels. Thus, the categories defined seem to be quite adequate for towns of this size range. Moreover, noise level predictive capacity of the method was also analyzed, and an overall value for the predictive capacity of 80% was obtained. Thus, our method can be a simple, low-cost strategy to make a statistical evaluation of the TN in a city.     

Hybridization,agency discretion,and implementation of the U.S. Endangered Species Act

The U.S. Endangered Species Act (ESA) requires that the “best available scientific and commercial data” be used to protect imperiled species from extinction and preserve biodiversity. However, it does not provide specific guidance on how to apply this mandate. Scientific data can be uncertain and controversial, particularly regarding species delineation and hybridization issues. The U.S. Fish and Wildlife Service (FWS) had an evolving hybrid policy to guide protection decisions for individuals of hybrid origin. Currently, this policy is in limbo because it resulted in several controversial conservation decisions in the past. Biologists from FWS must interpret and apply the best available science to their recommendations and likely use considerable discretion in making recommendations for what species to list, how to define those species, and how to recover them. We used semistructured interviews to collect data on FWS biologists’ use of discretion to make recommendations for listed species with hybridization issues. These biologists had a large amount of discretion to determine the best available science and how to interpret it but generally deferred to the scientific consensus on the taxonomic status of an organism. Respondents viewed hybridization primarily as a problem in the context of the ESA, although biologists who had experience with hybridization issues were more likely to describe it in more nuanced terms. Many interviewees expressed a desire to continue the current case‐by‐case approach for handling hybridization issues, but some wanted more guidance on procedures (i.e., a “flexible” hybrid policy). Field‐level information can provide critical insight into which policies are working (or not working) and why. The FWS biologists’ we interviewed had a high level of discretion, which greatly influenced ESA implementation, particularly in the context of hybridization.     

Assessing impacts on urban greenspace,waterways, and vegetation in urban planning

Parks, waterways, and vegetation enhance the well-being of urbanites and thus warrant consideration in planning and policy-making. It is, however, difficult to assess how land-use change may impact these features and how this in turn may impact well-being. I use a case-study approach to present a framework that combines geospatial and economic valuation techniques to generate indicators of the effects of land-use policies that alter these amenities on community well-being. This framework quantifies the impacts of land-use change on urban environmental amenities in a way that could help communities plan land use so as to maintain well-being as they urbanise.     

Expansion of Urban Space and Land Use Control in the Process of Urbanization: an Overview

Urban expansion brought by the rapid progress of urbanization has caused many problems in China. It is a significant issue to evaluate the extent of urban expansion and to make appropriate controls over the sprawl of urban areas. With a comparative study of international experiences, this article analyzed the mechanism and consequences of urban expansion, reviewed the typical planning and financial policies adopted by other countries for controlling urban sprawl, and discussed the suitable densities of urba...     

Environmental injustice of informal e-waste recycling in Agbogbloshie-Accra: urban political ecology perspective

This paper provides additional empirical knowledge of injustice embedded in the urban governance of informal-sector electronic waste (e-waste) recycling in Ghana. It uses Urban Political Ecology and Environmental Justice perspectives to explain how divergent interest and power among diverse actors in the e-waste sector engender social and environmental (in)justice in Accra. Using the case study approach, this paper reveals that the persistent struggles over interest and power which characterise the governance and management of informal e-waste recycling generate inequity, false accusations, misrecognition, disrespect, devaluation, neglect, exclusion, and abuse of freedom and rights. Inclusive of the finding is the development of local resistance and social movement in defence of interests and against state aggression, oppression, domination and neglect. The study concludes to suggest that the governance of urban socio-economic and ecological space of Accra should involve coordination, participation, holistic inclusion of diverse interest, so as to minimise trade-offs and reap synergies.     

Living the green city: Freiburg's Solarsiedlung between narratives and practices of sustainable urban development

The solar settlement (Solarsiedlung) in Freiburg, Germany, has been widely hailed as an eco-city or green city neighbourhood and a blueprint for sustainable urban development. However, as there is a noticeable lack of critical analysis of what constitutes Solarsiedlung as an “eco-city”, this paper studies narratives and practices of sustainable urban development. First, we look at Solarsiedlung as a best-practice model – a narrative that was produced and perpetuated by architects, urban planners, investors and academics celebrating this neighbourhood as a technologically leapfrogging, economically sound and socially integrated project. Second, we explore the everyday practices and lived experience of the residents in Solarsiedlung. Bringing together these two perspectives, we contribute to a more comprehensive understanding and critical reading of the interplay between the ecological, economic and social dimensions of sustainable development as seen from different viewpoints. Findings indicate that Solarsiedlung as a best-practice model is embedded in growth-oriented neoliberal strategies that are in conflict with the everyday practices and lived experience of the residents. Our findings put into question the widely assumed transferability of best-practice models in sustainable urban development.