An evolution perspective on the urban land carrying capacity in the urbanization era of China.

The past few decades witness a typical urbanization era in large developing countries such as China. In line with the urbanization process, land resources have inevitably presented a series of changes. The evolution of urban land carrying capacity (ULCC) is appreciated as a yardstick for guiding towards sustainable urban development. This paper therefore proposes an alternative method from carrier-load perspective for investigating the evolution of ULCC performance in China during the rapid urbanization era of 2012-2017. The data employed for analysis is collected from 290 Chinese prefectural-level cities. Results indicate that ULCC performance in the urbanizing China has been evolving towards a better state, for which 94% of the surveyed cities have made progress. However, significant disparity exists between cities on ULCC evolution performance, in particular, mega cities tend to have better ULCC evolution performance. Some cities may have better evolution performance although they have a poor average ULCC value. Contrarily, some cities may present poor evolution performance but they carry a better average ULCC value. The research findings provide valuable references not only for policy-makers to better understand the state of ULCC across the country, and appreciate inspiring experiences and lessons for implementing effective tailor-made measures to improve the ULCC performance, but also for enriching the literature in land resource management.

Destruction of inorganic municipal solid waste incinerator fly ash in a DC arc plasma furnace.

Due to the toxicity of dioxins, furans and heavy metals, there is a growing environmental concern on municipal solid waste incinerator (MSWI) fly ash in China. The purpose of this study is directed towards the volume-reduction of fly ash without any additive by thermal plasma and recycling of vitrified slag. This process uses extremely high-temperature in an oxygen-starved environment to completely decompose complex waste into very simple molecules. For developing the proper plasma processes to treat MSWI fly ash, a new crucible-type plasma furnace was built. The melting process metamorphosed fly ash to granulated slag that was less than 1/3 of the volume of the fly ash, and about 64% of the weight of the fly ash. The safety of the vitrified slag was tested. The properties of the slag were affected by the differences in the cooling methods. Water-cooled and composite-cooled slag showed more excellent resistance against the leaching of heavy metals and can be utilized as building material without toxicity problems.