Abstract:Tianjin is the largest coastal city in northern China with rapid economic development and urbanization. Energy-related CO2 emissions from Tianjin's production and household sectors during 1995-2012 were calculated according to the default carbon-emission coefficients provided by the Intergovernmental Panel on Climate Change. We decomposed the changes in CO2 emissions resulting from 12 causal factors based on the method of Logarithmic Mean Divisia Index. The examined factors were divided into four types of effects: energy intensity effect, structure effect, activity intensity effect, scale effect and the various influencing factors imposed differential impacts on CO2 emissions. The decomposition outcomes indicate that per capita GDP and population scale are the dominant positive driving factors behind the growth in CO2 emissions for all sectors, while the energy intensity of the production sector is the main contributor to dampen the CO2 emissions increment, and the contributions from industry structure and energy structure need further enhancement. The analysis results reveal the reasons for CO2 emission changes in Tianjin and provide a solid basis upon which policy makers may propose emission reduction measures and approaches for the implementation of sustainable development strategies.
This study analyzes Tianjin's eco-efficiency trends during the period [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010][2011][2012][2013] and reasons for their changes, with the aim of contributing to efforts to ensure the city's sustainable development. While eco-efficiency of all of the indicators that we analyzed showed improvements during the study period, a gap remained in comparison to the more advanced eco-efficiency observed both domestically and internationally. We subsequently introduced decoupling indices to examine the decoupling relationship between environmental pressure and economic growth. This analysis demonstrated that some progress occurred during the study period resulting from the implementation of existing policies and measures entailing resource conservation and reduction in the emission of pollutants. The latter applied, especially, to sulfur dioxide (SO2) and chemical oxygen demand (COD), which both retained strong decoupling states from 2006 to 2013. Other indicators showed an apparent tendency toward decoupling, but most displayed weak decoupling. These findings indicate that further efforts are urgently required to promote strong decoupling. At the end of the twelfth Five-Year Plan period, Tianjin should consider formulating policies from the perspectives of resource consumption and pollutant emissions reduction to promote further sustainable development.
Following successful abatement of external nutrient sources, one must shift the focus to the role of phosphorus (P) release from sediment. This enables us to better assess the causes for sustained eutrophication in freshwater ecosystem and how to deal with this challenge. In this study, five sediment cores from the shallow YuQiao Reservoir in northern China were investigated. The reservoir serves as the main raw water source for tap water services of Tianjin megacity, with a population of 15.6 million. Sediment characteristics and P fractions were determined in order to assess the role of the sediments as the P source to the water body. The total P content (TP) in sediments was similar to what was found in catchment soils, although the P sorption capacity of sediments was 7–10 times greater than for the catchment soils. Isotherm adsorption experiments documented that when P concentration in overlying water drops below 0.032–0.070 mg L−1, depending on the site, the sediment contributes with a positive flux of P to the overlying water. Adsorbed P at different depths in the sediments is found to be released with a similarly rapid release rate during the first 20 h, though chronic release was observed mainly from the top 30 cm of the sediment core. Dredging the top 30 cm layer of the sediments will decrease the level of soluble reactive phosphate in the water being sustained by the sediment flux of P.
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