The ecological footprint (EF) is a method for measuring sustainable development through ecological impact. A methodology is presented for predicting urban ecological footprints. Urban energy use and natural resource consumption were analyzed to calculate an EF based on land type (arable, pasture, forest, fossil energy land, built-up area and water area) and consumption (food, housing, transportation, goods, services and waste). The result was then compared with the local ecological carrying capacity to develop criteria for sustainable ecological footprints. Case studies of four cities in China (Guangzhou, Ningbo, Suzhou and Yangzhou) illustrate the urban EF approach. The time series of EF in a case study of Guangzhou for 1991–2001 was analyzed and the consumption–land-use matrix of urban EF was established. The results show that the cities are ecologically unsustainable, with average ecological conflicts per capita of more than 2 ha. The urban EF method is useful to measure urban sustainable development and provides policy proposals for decision-making. However, the EF method still has limitations and weaknesses. 相似文献
In this research, supercritical carbon dioxide extraction (SFE) showed better extraction effect when compared with Solid- liquid extraction (SLE), Soxhlet extraction (SE) and Ultrasonic extraction (UE), not only in the rate but also the time. The comparison among these three extraction modifiers, including acetone, ethanol and methanol demonstrated that ethanol was preferred to SFE due to its high extraction effect and low toxicology. In addition, parameter of SFE, influence of temperature and pressure were investigated, and the best extraction effect was achieved at the optima conditions, temperature of 40°C and the pressure of 35 MPa. Thus, SFE is a highly effective method for flavonols extraction, requiring minimum energy and producing non-toxic byproduct. SFE-GC system is applied for the evaluation on flavonols that plays a key role in plant resistance to heavy metal, with its content and synthetase gene expression significantly increasing in plant when threatened by heavy metal. Besides, results indicated that flavonols can improve plant resistance to oxidative stress by quenching the redundant ROS in matrix.
Although Beijing has carried out municipal solid waste (MSW) source separation since 1996, it has largely been ineffective. In 2012, a “Green House” program was established as a new attempt for central sorting. In this study, the authors used material flow analysis (MFA) and cost benefit analysis (CBA) methods to investigate Green House’s environment and economic feasibility. Results showed that the program did have significant environmental benefits on waste reduction, which reduced the amount of waste by 34%. If the Green House program is implemented in a residential community with wet waste ratio of 66%, the proportion of waste reduction can reach 37%. However, the Green House is now running with a monthly loss of 1982 CNY. This is mainly because most of its benefits come from waste reduction (i.e., 5878 CNY per month), which does not turn a monetary benefit, but is instead distributed to the whole of society as positive environmental externalities. Lack of government involvement, small program scale, and technical/managerial deficiency are three main barriers of the Green House. We, thus, make three recommendations: involve government authority and financial support, expand the program scale to separate 91.4 tons of waste every month, and use more professional equipment/technologies. If the Green House program can successfully adopt these suggestions, 33.8 tons of waste can be reduced monthly, and it would be able to flip the loss into a profit worth 35034 CNY.
