Carpenter A C, Gardner K H, Fopiano J, Benson C H, Edil T B
Recycled Materials Resource Center, 35 Colovos Road, Gregg Hall, University of New Hampshire, Durham, NH 03824, USA.
Waste Manag. 2007;27(10):1458-64. doi: 10.1016/j.wasman.2007.03.007. Epub 2007 May 17.
This paper uses a life-cycle assessment (LCA) framework to characterize comparative environmental impacts from the use of virgin aggregate and recycled materials in roadway construction. To evaluate site-specific human toxicity potential (HTP) in a more robust manner, metals release data from a demonstration site were combined with an unsaturated contaminant transport model to predict long-term impacts to groundwater. The LCA determined that there were reduced energy and water consumption, air emissions, Pb, Hg and hazardous waste generation and non-cancer HTP when bottom ash was used in lieu of virgin crushed rock. Conversely, using bottom ash instead of virgin crushed rock increased the cancer HTP risk due to potential leachate generation by the bottom ash. At this scale of analysis, the trade-offs are clearly between the cancer HTP (higher for bottom ash) and all of the other impacts listed above (lower for bottom ash). The site-specific analysis predicted that the contaminants (Cd, Cr, Se and Ag for this study) transported from the bottom ash to the groundwater resulted in very low unsaturated zone contaminant concentrations over a 200 year period due to retardation in the vadose zone. The level of contaminants predicted to reach the groundwater after 200 years was significantly less than groundwater maximum contaminant levels (MCL) set by the US Environmental Protection Agency for drinking water. Results of the site-specific contaminant release estimates vary depending on numerous site and material specific factors. However, the combination of the LCA and the site specific analysis can provide an appropriate context for decision making. Trade-offs are inherent in making decisions about recycled versus virgin material use, and regulatory frameworks should recognize and explicitly acknowledge these trade-offs in decision processes.
本文采用生命周期评估（LCA）框架来描述道路建设中使用原生骨料和再生材料所产生的相对环境影响。为了更全面地评估特定场地的人体毒性潜力（HTP），将一个示范场地的金属释放数据与一个非饱和污染物迁移模型相结合，以预测对地下水的长期影响。生命周期评估确定，当使用底灰替代原生碎石时，能源和水的消耗、空气排放、铅、汞和危险废物的产生以及非致癌性人体毒性潜力均有所降低。相反，由于底灰可能产生渗滤液，使用底灰替代原生碎石会增加致癌性人体毒性潜力风险。在这种分析尺度下，权衡显然存在于致癌性人体毒性潜力（底灰较高）与上述所有其他影响（底灰较低）之间。特定场地分析预测，由于包气带的阻滞作用，在200年的时间里，从底灰迁移到地下水的污染物（本研究中的镉、铬、硒和银）导致非饱和带污染物浓度非常低。预计200年后到达地下水的污染物水平显著低于美国环境保护局设定的饮用水地下水最大污染物水平（MCL）。特定场地污染物释放估计结果因众多场地和材料特定因素而异。然而，生命周期评估和特定场地分析的结合可以为决策提供适当的背景。在决定使用再生材料还是原生材料时，权衡是固有的，监管框架应在决策过程中认识并明确承认这些权衡。
