Wang Jianlong, Zhang Pingping, Yang Liqiong, Huang Tao
Key Laboratory of Urban Stormwater System and Water Environment, (Beijing University of Civil Engineering and Architecture), Ministry of Education, Beijing 100044, China.
Key Laboratory of Urban Stormwater System and Water Environment, (Beijing University of Civil Engineering and Architecture), Ministry of Education, Beijing 100044, China.
J Contam Hydrol. 2016 Feb-Mar;185-186:42-50. doi: 10.1016/j.jconhyd.2016.01.002. Epub 2016 Jan 8.
Bioretention technology, a low-impact development stormwater management measure, was evaluated for its ability to remove heavy metals (specifically cadmium, Cd) from urban stormwater runoff. Fine sand, zeolite, sand and quartz sand were selected as composite bioretention media. The effects of these materials on the removal efficiency, chemical forms, and accumulation and migration characteristics of Cd were examined in laboratory scale bioretention columns. Heretofore, few studies have examined the removal of Cd by bioretention. A five-step sequential extraction method, a single-contamination index method, and an empirical migration equation were used in the experiments. The average Cd removal efficiency of quartz sand approached 99%, and removal by the other media all exceeded 90%. The media types markedly affected the forms of Cd found in the columns as well as its vertical migration rate. The Cd accumulated in the four media was mainly in residual form; moreover, accumulation of Cd occurred mainly in the surface layer of the bioretention column. The migration depth of Cd in the four media increased with elapsed time, in the following sequence: zeolite>quartz sand>fine sand>sand. In contrast, the migration rate decreased with elapsed time, and the migration rate of Cd was lowest in sand (0.015 m per annum over the first ten years). The comprehensive risk index analysis indicated that the risk arising from Cd discharge to surface water was "intermediate", and that the degree of risk was lowest in sand, then quartz sand, zeolite, and fine sand in sequence. These results indicate that the adsorption and accumulation of Cd in the four media are more significant than the migration of Cd. In addition, the results of Cd risk assessment for the effluent indicate that each of the four media can serve as long-term adsorption material in a bioretention facility for purifying stormwater runoff.
生物滞留技术是一种低影响开发的雨水管理措施，本研究评估了其从城市雨水径流中去除重金属（特别是镉，Cd）的能力。选择细砂、沸石、砂和石英砂作为复合生物滞留介质。在实验室规模的生物滞留柱中研究了这些材料对Cd去除效率、化学形态以及积累和迁移特性的影响。迄今为止，很少有研究考察生物滞留对Cd的去除情况。实验采用五步连续提取法、单污染指数法和经验迁移方程。石英砂对Cd的平均去除效率接近99%，其他介质的去除率均超过90%。介质类型显著影响柱中Cd的形态及其垂直迁移速率。四种介质中积累的Cd主要以残留态存在；此外，Cd的积累主要发生在生物滞留柱的表层。Cd在四种介质中的迁移深度随时间增加，顺序为：沸石>石英砂>细砂>砂。相比之下，迁移速率随时间降低，Cd在砂中的迁移速率最低（前十年年均迁移0.015米）。综合风险指数分析表明，Cd排放到地表水产生风险为“中级”，风险程度在砂中最低，其次是石英砂、沸石和细砂。这些结果表明，四种介质对Cd的吸附和积累作用比Cd的迁移作用更显著。此外，对流出物的Cd风险评估结果表明，四种介质均可作为生物滞留设施中净化雨水径流的长期吸附材料。
