Department of Municipal Engineering, School of Civil Engineering, Southeast University, No. 2 Southeast University Road, Nanjing Jiangsu Province, 211189, China.
Environ Sci Pollut Res Int. 2021 Dec;28(47):67736-67747. doi: 10.1007/s11356-021-15350-y. Epub 2021 Jul 14.
This study investigated the effects of AgNPs on pollutant removals in constructed wetlands (CWs) with different flow patterns and spatial distributions of silver. Before exposure to AgNPs, upward flow constructed wetland (UCW) had better nitrogen removal than down-flow CW (DCW). And 0.5 mg/L AgNPs evidently inhibited nitrogen and phosphorus removal, including ammonia, nitrate, and TP (total phosphorus), with average effluent concentrations increasing by 70.83% of NH-N in UCW, 18.75% of TP in UCW, and 28.33% and 25.06% of NO-N in DCW and UCW, respectively, while COD (chemical oxygen demand) was not affected. Moreover, presence of 2 mg/L AgNPs slightly inhibited organic compounds and NH-N removal in two systems during stage 4 (dosing 2 mg/L AgNPs). However, the response of NO-N and TN removal to 2 mg/L AgNPs in two systems were different, and nitrogen concentrations in effluent at the end of stage 4 significantly increased in DCW. Addition of 2 mg/L AgNPs significantly affected TP removal in two systems. Two wetlands showed high removal efficiencies of about 98% on AgNPs, indicating that CWs could provide a feasible approach for ecological restoration of nanoparticles pollution. This study also found that AgNPs mainly accumulated in the upper layer with the Ag content of 17.55-20.26 mg/kg dry weight in sand layer and 7.25-10.85 mg/kg dry weight in gravel layer. Plant roots absorbed AgNPs, with Ag content at 50.80-101.40 mg/kg and bioconcentration factors 2.80-5.00. The obtained results showed that up-flow CWs had better performance and higher resistance to the exposure of AgNPs pollution, compared with down-flow CWs.
本研究探讨了不同银空间分布和流动模式的人工湿地（CWs）中 AgNPs 对污染物去除的影响。在暴露于 AgNPs 之前，上流式人工湿地（UCW）的氮去除效果优于下流式 CW（DCW）。并且 0.5mg/L 的 AgNPs 明显抑制了氮和磷的去除，包括氨、硝酸盐和总磷（TP），UCW 中 NH-N 的出水浓度增加了 70.83%，UCW 中 TP 增加了 18.75%，DCW 和 UCW 中 NO-N 分别增加了 28.33%和 25.06%，而 COD（化学需氧量）不受影响。此外，在第 4 阶段（投加 2mg/L 的 AgNPs），2mg/L 的 AgNPs 略微抑制了两个系统中有机化合物和 NH-N 的去除。然而，两个系统中 2mg/L AgNPs 对 NO-N 和 TN 去除的响应不同，在 DCW 中，第 4 阶段结束时出水中的氮浓度显著增加。添加 2mg/L 的 AgNPs 显著影响了两个系统中 TP 的去除。两个湿地对 AgNPs 的去除率均高达 98%左右，表明 CWs 可为纳米粒子污染的生态修复提供一种可行的方法。本研究还发现，AgNPs 主要积累在沙层中 17.55-20.26mg/kg 干重和砾石层中 7.25-10.85mg/kg 干重的上层，植物根系吸收 AgNPs，Ag 含量为 50.80-101.40mg/kg，生物浓缩系数为 2.80-5.00。结果表明，与下流式 CW 相比，上流式 CW 具有更好的性能和更高的抗 AgNPs 污染暴露能力。
