Effects of Urban Metabolism on the Well Water Quality in Cotonou (Benin) and Lomé(Togo)

Urban metabolism, a process of material, energy and water flows, consumption or transformation in the cities and outflows of wastes, has impacts on the shallow groundwater. This study addressed the relationship between the urban metabolic system and well water physicochemical and bacteriological quality in the coastal cities of Cotonou and Lomé. A participatory transdisciplinary approach, involving non-academics and academics stakeholders was used to analyse urban inflows and outflows related to groundwater quality. Standard methods were used to measure well water quality from 100 seasonal samples. Waste management revealed poor sanitation and hence a linear urban metabolism with no solid and liquid wastes and excreta recycling. This form of city metabolism reinforced by the seawater inflow is the main source of groundwater quality deterioration in Cotonou and Lomé. The principal water types Ca2+–Mg2+–Cl-– SO2-4 (48.21%), Na+–K+–Cl-–SO2-4 (65.9%) and the Gibbs diagram suggested water-rock interactions and dominance of cations exchange on the hydrogeological compositions, also seasonally controlled by saltwater intrusion or anthropogenic salinization. The water quality index on the range of 35.90 to 169.60 in Cotonou and 82.94 to 364.68 in Lomé indicated well water very poor quality to unsuitable for drinking. Moreover, the bacteriological quality was bad due to total coliforms (112 - 1812;1 - 1000 UFC/100 mL respectively in Cotonou and Lomé), Escherichia coli (40 - 780;1 - 112 UFC/100 mL), faecal enterococci/streptococcus (18 - 736;1 - 118 UFC/100 mL). The findings could help to sustain groundwater quality by controlling the pollution sources linked to urban metabolism.

Analysis and Evaluation of the Ecological Restoration of the City with an Emphasis on Urban Metabolism

It would not be far-fetched to say that people’s lives depend on their environment and its quality. With growing urbanization of this dependence is growing increasingly urban environment. Urbanization not only balances economic and social development in the cities but also stirs the regional ecological imbalances and the natural areas. In addition to these problems, there is disruption of water, air, soil and environment built on imbalances between urban areas and the lack of social vitality and frustration. All cities, especially metropolitan with developing economies face to uncertainty in terms of health, environment and quality of life. This article utilizes the ecological and environmental issues and integrates it with urban metabolism approach to the study’s revival of urban ecology, something that results in enhanced quality of life for citizens. This research is the theoretical and analytical method. In the research process of this study, related domestic and foreign literature subsequently of traditional and electronic library resources, books and articles published in journals have been used. According to the type of research in this study, descriptive analysis was performed. Based on findings of this study, urban ecology is a tool to control and guide of urban growth and activities in a way to improve quality of urban environment. Applying urban ecology in designing cities has provided opportunities to create practical ecological systems. By using them, natural process, human activities and urban environment could be combined. Moreover, urban metabolism as an indicator of urban sustainability and a part of urban ecology includes two main related and non-contra-dictory approaches of odum and MFA. Due to difficulties which modern cities face to, benefiting and applying these approaches seem vital.

Material dependence of cities and implications for regional sustainability

Cities rely on massive amounts of physical,chemical,and biological resources to support their growth and metabolism.These‘metabolic inputs’are accumulated in cities to form material stocks in buildings,infrastructures,transportation facilities,and household appliances.This study takes China’s urbanization as an example to illustrate the characteristics of material stock changes in developing countries and compare them with those in developed countries.Results show that(1)material stocks have been growing in China,but have saturated in developed countries,and(2)the major components of urban metabolism are construction and industrial materials(e.g.,steel)in developing countries but biomass(e.g.,food)in developed countries.The changes in the magnitude and types of material stocks can not only measure urban development but also directly link city and its residents,offering advantages in representing urbanization over the existing indices such as population,land use,or gross domestic product(GDP).Given the new insights provided by material stock,we recommend to embrace it as a critical index of urbanization for guiding urban planning and policy-making.

Dynamic simulation of urban water metabolism under water environmental carrying capacity restrictions

A revised concept for urban water metabolism （UWM） is presented in this study to address the inadequacies in current research on UWM and the problems associated with the traditional urban water metabolic process. Feedback loops can be analyzed to increase the water environmental carrying capacity （WECC） of the new urban water metabolism system （UWMS） over that of a traditional UWMS. An analysis of the feedback loops of an UWMS was used to construct a system dynamics （SD） model for the system under a WECC restriction. Water metabolic processes were simulated for different scenarios using the Tongzhou District in Beijing as an example. The results for the newly developed UWM case showed that a water environment of Tongzhou District could support a population of 1.1926 × 106, an irrigation area of 375.521 km2, a livestock of 0.7732 × 106, and an industrial value added of ￥193.14 × 109 （i.e. about US$28.285 × 109） in 2020. A sensitivity analysis showed that the WECC could be improved to some extent by constructing new sewage treatment facilities or by expanding the current sewage treatment facilities, using reclaimed water and improving the water circulation system.

Multi-scale integrated assessment of urban energy use and CO_2 emissions

Accurate and detailed accounting of energy-induced carbon dioxide （CO_2） emis- sions is crucial to the evaluation of pressures on natural resources and the environment, as well as to the assignment of responsibility for emission reductions. However, previous emission inventories were usually productionor consumption-based accounting, and few studies have comprehensively documented the linkages among socio-economic activities and external transaction in urban areas. Therefore, we address this gap in proposing an analytical framework and accounting system with three dimensions of boundaries to comprehensively assess urban energy use and related CO_2 emissions. The analytical framework depicted the input, transformation, transfer and discharge process of the carbon-based （fossil） energy flows through the complex urban ecosystems, and defined the accounting scopes and boundaries on the strength of ＇carbon footprint＇ and ＇urban metabolism＇. The accounting system highlighted the assessment for the transfer and discharge of socio-economic subsystems with different spatial boundaries. Three kinds methods applied to Beijing City explic- itly exhibited the accounting characteristics. Our research firstly suggests that urban carbon-based energy metabolism can be used to analyze the process and structure of urban energy consumption and CO_2 emissions. Secondly, three kinds of accounting methods use different benchmarks to estimate urban energy use and CO_2 emissions with their distinct strength and weakness. Thirdly, the empirical analysis in Beijing City demonstrate that the three kinds of methods are complementary and give different insights to discuss urban energy-induced CO_2 emissions reduction. We deduce a conclusion that carbon reductions responsibility can be assigned in the light of production, consumption and shared responsibility based principles. Overall, from perspective of the industrial and energy restructuring and the residential lifestyle changes, our results shed new light on the analysis on the evolutionary mechanism and pattern of urban energy-induced CO_2 emissions with the combination of three kinds of methods. And the spatial structure adjustment and technical progress provides further elements for consideration about the scenarios of change in urban energy use and CO_2 emissions.

Analysis of urban metabolic processes based on input-output method： model development and a case study for Beijing

Discovering ways in which to increase the sustainability of the metabolic processes involved in urbanization has become an urgent task for urban design and management in China. As cities are analogous to living organisms, the disorders of their metabolic processes can be regarded as the cause of ＂urban disease＂. Therefore, identification of these causes through metabolic process analysis and ecological element distribution through the urban ecosystem＇s compartments will be helpful. By using Beijing as an example, we have compiled monetary input- output tables from 1997, 2000, 2002, 2005, and 2007 and calculated the intensities of the embodied ecological elements to compile the corresponding implied physical input-output tables. We then divided Beijing＇s economy into 32 compartments and analyzed the direct and indirect ecological intensities embodied in the flows of ecological elements through urban metabolic processes. Based on the combination of input-output tables and ecological network analysis, the description of multiple ecological elements transferred among Beijing＇s industrial compartments and their distribution has been refined. This hybrid approach can provide a more scientific basis for management of urban resource flows. In addition, the data obtained from distribution characteristics of ecological elements may provide a basic data platform for exploring the metabolic mechanism of Beijing.

Assessing urban low-carbon performance from a metabolic perspective

How to mitigate anthropogenic carbon emissions in cities determines to a large degree whether global temperature targets in this century are to be met.Using 12 cities in or outside China as case studies,we quantified the critical processes of carbon metabolism based on the urban carbon metabolism assessment framework(CMAF)proposed.The differences of sector contribution,and per capita and intensity among carbon throughflows,carbon inflows and carbon emissions were evaluated.Furthermore,we established an indicator system for CMAF consisting of flow-based and structural indicators to compare the low-carbon performances of cities.The results showed that the total carbon throughflow(TCT)and total carbon inflow(TCI)in Chinese cities were 7–12%higher than in European and American cities regarding the manufacturing and services sector on average,but 6–9%lower in the household consumption sector.Beijing,Tianjin,Nanjing and Guangzhou had lower per capita TCT and TCI than in European and American cities such as Paris and Los Angeles,while their carbon intensities were about three times as much.The per capita TCT in a city was found significantly correlated with per capita energy consumption and had a certain correlation with per capita building or housing area.This study found that TCT,TCI and carbon dioxide emission each provided unique information to measure the potential climatic impact of cities.The difference in the ranking of low-carbon performance between the investigated cities was significant both in terms of flow-based and structural indicators.We suggest these assessment indicators of carbon metabolism be integrated into urban resources management to reflect both the decarbonization status and future emission reduction potential more accurately and to provide systemic decision support for achieving the goal of carbon neutrality in cities.

Nexus security： governance, innovation and the resilient city

Nexus security is a compound mix of ideas： reconciling human needs and wants with access to multiple resources; diversity of access to those resources and services; resilience in the face of weather- and climate- related variability; resilience likewise in the face of infrastructure failure; and the personal, individual sense of belonging. At the level of Systems Thinking there is a very close relationship between resilience in the behavior of natural （ecological） systems and resilience in the social dynamics of governance within communities, where such resilience establishes the viability of these communities over centuries, which in turn entails successful stewardship of the man-environment relationship. We use insights from this cross-system mapping -- across natural, built, and human systems -- to assess, first, the role of city governance in achieving nexus security （or not） and, second, the role of technological innovations in serving the same purpose. More specifically, eight principles, covering resilience and diversity of access to resources and services, are used to gauge security-enhancing features of city buildings and infrastructure. Case studies include new designs of resilient office blocks, nutrient （nitrogen and phosphorus） recovery systems for sanitation and waste- water treatment, and the reconstruction of urban parks for the provision of ecosystem services. Throughout the paper, matters of risk in the face of meteorological variability are prominent. We do not conclude, however, that the presence of risk implies nexus insecurity.