Effect of seaweed proliferation on benthic habitat quality assessed by Sediment Profile Imaging

Changes in sediment quality, with special reference to benthic habitat conditions resulting from macroalgae overgrowth, were studied in the Venice Lagoon, Italy. Data were collected biweekly in spring and summer from 1993 to 1998 and from 2001 to 2002, as part of the macroalgae growth control strategies managed by the Venice Water Authority-Consorzio Venezia Nuova. Benthic habitat conditions were studied by means of Sediment Profile Imaging, which allowed the collection of several variables: aRPD (apparent redox potential discontinuity), prism penetration depth, presence of anoxia on the surface of the sediment, presence of reduced gas bubbles, stage of benthic colonization. All these variables led to the calculation of an environmental index (Organism–Sediment Index, OSI), which was then related to physical variables and macroalgae abundance. Until 1996, the overall benthic habitat of the Venice Lagoon showed almost stressed conditions; from 1997, the seaweed biomass rapidly declined and the OSI increased significantly. The OSI seemed to be affected by seaweed biomass, sediment compactness and water depth. Macroalgae biomass greater than 4.5 kg/m² led to the complete disappearance of stage III of benthic colonization; values as low as 0.70 kg m² already had a severe impact on recolonization. SPI attributes indicated the main mechanisms that could have contributed to the benthic quality: seaweed proliferation is often followed by rapid decay of macroalgae biomass, especially when present in large amounts. The decrease in seaweed biomass often results in oxygen depletion in the water column and thus in the sediment, preventing complete benthic colonization. This research confirms the importance of in situ rapid reconnaissance surveys to assess the impact of eutrophication on the benthic habitat.     

以改革创新精神推进公交服务品牌建设

成功的品牌是靠优质的服务和优良诚信的经营风格来打造的.如何打造叫得响的企业服务品牌,对企业的改革发展至关重要.     

Home-work carpooling for social mixing

Transportation - Shared mobility is widely recognized for its contribution in reducing carbon footprint, traffic congestion, parking needs and transportation-related costs in urban and suburban...     

Current publications

Despite the European Union (EU) efforts promoting policies that encourage short sea shipping (SSS) based on its advantages in terms of intermodality and environment, this mode has not yet reached a significant market share compared to land transport. In this paper, we establish a thesis that suggests that funding programs (such as Marco Polo I and II) have not properly offered the right incentives to promote SSS, and aspects such as the key role of port infrastructure and its characteristics, have not been taken into consideration. In a departure from traditional transport cost models, to prove our thesis, we use a theoretical intermodal competition model to compare alternative modes—road transport vs. SSS. We reach the conclusion that the EU needs to focus on ports and transport system efficiency as a whole in order to compete effectively in the freight transport market.     

基于SP调查的天津市居民出行行为时间价值

为揭示天津市居民出行行为时间价值的一般规律,采用SP调查中的卡片式面谈调查法,运用市场细分法确定调查规模及抽样率,采用计算包容性检查矩阵等数据处理手段,估算天津市居民出行行为时间价值。比较了出行行为时间价值与单位工作时间价值之间的关系,并分析了不同出行方式、出行目的、出行时段的时间价值,研究了出行收入与时间价值的变化规律。得出现阶段天津市居民出行行为时间价值的分布,表明大部分出行者不愿为出行支付较高费用,但随着收入增加,出行行为时间价值将会快速增长,使个体机动化出行方式的需求增大,城市出行方式结构可能出现拐点。     

Public private partnerships in transportation: Some insights from the European experience

Most EU member states and the European Commission regard the PPP as an important tool to attract additional financial resources for high priority investments such as transport. The objective of this paper is to delineate the EU panorama of PPP markets and investigate the impacts of EU institutions in the development and success of this type of financial arrangement for the transport sector in Europe. We examine how the scope of the PPP in Europe is based on the flexibility and adaptability of the contract to the features of the project and to the economic and institutional environment. These issues are illustrated through a number of examples in the transport sector. We conclude by observing that the market for PPPs, although still fragmented nationally, is developing a European dimension and attracting resources from a variety of players.     

Does the political and economic context influence the success of a transport project? An analysis of transport public-private partnerships

The construction and provision of infrastructure services such as transport nowadays is often based on a partnership between three main actors: public sector, private sector and multilateral lenders, under a framework of Public-Private Partnerships (PPPs). This type of partnership has been employed in a wide range of projects in the transport sector and in various contexts in developing and developed countries. Given this observation, the objective of this paper is to examine how countries’ economic and political characteristics contribute to the success of PPPs in transport investments. Special focus in the analysis is given to how the perception of corruption and democratic accountability may influence the success of a PPP project in different transport sectors. We examine a database with 856 transport PPP projects using a generalized linear model in the form of a logit model in order to evaluate the transport database covering data from 72 countries, classified in six regions. The study highlights the importance of national experience. Not only does national macroeconomic experience appear to have a relevant role, but so also does its past experience (either positive or negative) of transport PPP projects. An interesting finding from the analysis is the importance of the rest of the world’s perception of a country’s level of corruption and democratic accountability for the final outcome of a PPP project.