Quasi-dynamic leaching characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from raw and solidified air pollution control (APC) residues were examined via a nine-time multiple leaching test. The effect of injected activated carbon in the APC residues on the PCDD/F leachability was also evaluated. When humic acid solution was used as a leachant, the leaching concentrations of PCDD/Fs fluctuated between the first and the fifth leaching, followed by a gradual increase and then suddenly reached maximum values at the leaching sequences around seventh and eighth. This significant enhancement in PCDD/F leachability was mainly due to an increase in the release of highly chlorinated PCDD/Fs. Leaching of PCDD/Fs with n-hexane was, in contrast, primarily caused by the partitioning of hydrophobic PCDD/Fs between the APC residue surface and the liquid phase of n-hexane. Consequently, the largest leaching concentrations for n-hexane tests achieved at the first leaching, followed by a decrease and reached plateaus. Solidification/stabilization (S/S) decreased the PCDD/F leachability up to the fifth leaching by the use of humic acid solution. However, S/S increased the PCDD/F leaching concentrations and rates with n-hexane. The activated carbon in APC residues significantly inhibited the release of PCDD/F with n-hexane. The inhibiting effect provided by activated carbon was, however, less significant by the use of humic acid solution. 相似文献
Abstract Rapid urbanization in Beijing stimulates the urban land expansion and diminishes available agricultural land. Monofunctional agricultural land use can not meet the demand of the development of the multifunctional agriculture and urbanization any more, so multifunctional agricultural land use is going to be promoted in the city. This article proposes the evolvement of the land use change from 1992 to 2004 and discusses some evolvement views. 相似文献
The continuous increase in waste generation warrants global management of waste to reduce the adverse economic, social, and environmental impact of waste while achieving goals for sustainability. The complexity of waste management systems due to different waste management practices renders such systems difficult to analyze. System dynamics (SD) approach aids in conceptualizing and analyzing the structure, interactions, and mode of behavior of the complex systems. The impact of the underlying components can therefore be assessed in an integrated way while the impact of possible policies on the system can be studied to implement appropriate decisions. This review summarizes various applications of SD pertinent to the waste management practices in different countries. Practices may include waste generation, reduction, reuse/recovery, recycling, and disposal. Each study supports regional-demanding targets in environmental, social, and economic scopes such as expanding landfill life span, implementing proper disposal fee, global warming mitigation, energy generation/saving, etc. The interacting variables in the WMS are specifically determined based on the defined problem, ultimate goal, and the type of waste. Generally, population and gross domestic product can increase the waste generation. An increase in waste reduction, source separation, and recycling rate could decrease the environmental impact, but it is not necessarily profitable from an economic perspective. Incentives to separate waste and knowledge about waste management are variables that always have a positive impact on the entire system.
