建筑废物填海处置过程重金属浸出特性及环境影响

填海处置已成为滨海城市建筑废物的重要消纳途径，而海水侵蚀导致重金属浸出可能加剧环境风险.为探究不同类型建筑废物中重金属受海水侵蚀的浸出特性及环境影响，于深圳市的城中村拆除作业现场、建筑装饰装修工程现场、建筑废物资源化利用厂、建筑垃圾堆填场开展不同来源建筑废物样品采集，分析样品中w（Zn）、w（Pb）、w（Cu）、w（Cd），评价其潜在环境风险并解析其产生源；在此基础上，参考固体废物毒性浸出方法开展海水浸出模拟试验.结果表明:①建筑废物中重金属的潜在环境风险程度依次表现为Zn > Pb > Cu > Cd，w（Zn）、w（Pb）、w（Cu）、w（Cd）的最大值依次为197.8、82.6、67.1、0.22 mg/kg，分别为广东省土壤环境背景值的3.8、2.2、3.7和2.2倍，且来源于砖块、瓷砖、砂浆块、墙面涂料和玻璃的重金属含量超过了围填海工程填充物质成分限值要求.②海水对废物中重金属浸出影响显著，在液固比为10:1、浸出时间为18 h条件下，Zn、Pb、Cu、Cd浸出率分别高达15.9%、82.0%、10.4%和57.4%.③随着液固比和浸出时间的增加，重金属浸出量呈明显的上升趋势，其中Pb的浸出量最高.鉴于此，一方面应完善海水侵蚀对建筑废物中重金属浸出给沿海环境带来的生态风险分析；另一方面在填海处置前应加强建筑废物的风险管理如分类收集和安全处置等，并建立相应的控污机制. 

Performance and Leaching Characteristics of Heavy Metals from Construction and Demolition Waste for Disposal of Sea Land Reclamation

Sea land reclamation in many coastal cities has become an important way to dispose the construction and demolition (C & D) waste. However, heavy metal leaching may exacerbate the environmental risks of sea land reclamation activities. In order to investigate the leaching characteristics and environmental effects of heavy metals from C & D waste induced by seawater erosion, the concentrations of Zn, Pb, Cu and Cd were therefore determined to assess the potential environmental risk and the pollutant sources, samples were collected from urban village demolition site, building decoration project site, C & D waste recycling plant and C & D waste landfill site in Shenzhen City. Based on that, the simulation experiments of seawater leaching were further carried out with reference to the method of''solid waste-extraction procedure for leaching toxicity''. The results indicated that:(1) The potential environmental risks posed by the heavy metals in different C & D waste rank in the following sequence:Zn > Pb > Cu > Cd, the highest concentrations of Zn, Pb, Cu and Cd were 197.8, 82.6, 67.1 and 0.22 mg/kg respectively, which were 3.8, 2.2, 3.7 and 2.2 times higher than the values set in Guangdong Province Soil Background Standard. The sorting of brick, tile, mortar, coating and glass should be carried out before landfill according to the heavy metal concentrations exceeded the limitation on infilling components of sea reclamation and enclosure project; (2) Seawater had a significant effect on heavy metal leaching. The leaching rates of Zn, Pb, Cu and Cd reached 15.9%, 82.0%, 10.4% and 57.4% respectively when the liquid-solid ratio was 10:1 and the leaching time was 18 h. (3) With the increasing of liquid-solid ratio and leaching time, the leaching quantities of heavy metals showed an upward trend, Pb was the major contributing element which would affect the marine environment in the process of simulation. As a result, the ecological risk analysis of heavy metals leaching from C & D waste induced by seawater erosion should be improved. Meanwhile, the management of C & D waste such as waste sorting and safe disposal should be strengthened before reclamation, and pollution controlling should be well established.