Bioretention systems have been proved to be a natural approach for effectively reducing stormwater runoff pollution loads. However, the effects of heavy metals in stormwater runoff on microbial characteristics and organics removal in bioretention systems are unclear. In this study, two lab scale bioretention columns including the control and lead (Pb) treatment with the soil and filler layer were established. The changes of organic matter and lead in the effluent water and the soil (or fillers) were monitored during 121 operation days. The soil (or fillers) microbial characteristics were also analyzed. The results showed that most of Pb was intercepted by soil, while a small amount accumulated in fillers after 121 days. The long-term Pb accumulation in the biorentention system negatively affected the microbial biomass and microbial activity, while positively affected the community diversity. Pb accumulation killed some microorganisms, but simultaneously stimulated the growth of some Pb-tolerance microorganisms. The abundance of bacteria with COD degradation function in soil layer decreased, while that in fillers increased, indicating the effect of Pb on the community structure of these two layers was different. The COD removal in the soil and filler layer was promoted and inhibited by Pb contamination respectively. Moreover, Pb affected the removal of organic matter by chelating organic matters and changing their composition. The results suggested that the long-term accumulation of heavy metals in bioretention system would affect microbial degradation function and pollutants removal, causing our concern for the long-term maintenance of the bioretention system.

中文翻译：

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雨水径流中的铅（Pb）对生物截留系统中微生物特征和有机物去除的影响。

生物保留系统已被证明是有效减少雨水径流污染负荷的自然方法。但是，雨水径流中的重金属对微生物特征和生物保留系统中有机物去除的影响尚不清楚。在这项研究中，建立了两个实验室规模的生物保留柱，包括对照和铅（Pb）处理的土壤和填料层。在121个工作日内监测了废水和土壤（或填料）中有机物和铅的变化。还分析了土壤（或填料）的微生物特性。结果表明，121天后，大部分Pb被土壤截留，而少量的Pb被积累在填料中。生物保留系统中长期的Pb积累会对微生物生物量和微生物活性产生负面影响，同时对社区多样性产生积极影响。铅的积累杀死了一些微生物，但同时刺激了某些耐铅微生物的生长。土壤层中具有COD降解功能的细菌数量减少，而填料中的数量增加，这表明Pb对这两层群落结构的影响不同。铅污染分别促进和抑制了土壤和填料层中COD的去除。此外，铅通过螯合有机物并改变其组成影响了有机物的去除。结果表明，生物滞留系统中重金属的长期积累会影响微生物的降解功能和污染物的去除，引起我们对生物滞留系统的长期维护的关注。