Pi Na, Wu Yan, Zhu Hao Wen, Wong Yuk Shan, Tam Nora Fung Yee
Department of Chemistry, City University of Hong Kong, Hong Kong SAR, China; NUS Environmental Research Institute, National University of Singapore, Singapore.
Department of Chemistry, City University of Hong Kong, Hong Kong SAR, China.
Environ Pollut. 2017 Dec;231(Pt 1):104-114. doi: 10.1016/j.envpol.2017.07.085. Epub 2017 Aug 7.
Wastewater often contains mixed toxic pollutants, and the contribution of plant uptake in constructed wetland treatment systems is affected by environmental conditions, particularly tidal flushing. In this study, the uptake of wastewater-borne pollutants, including a mixture of polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs) congeners, by two mangrove plant species, namely Excoecaria agallocha L. and Kandelia obovata Sheue, Liu & Yong, under different tidal flushing regimes was investigated. Results showed that Fe plaque formed on root surfaces could immobilize wastewater-borne PAHs and PBDEs. At the end of 8-month wastewater treatment, most of the pollutants removed by plants ended up in Fe plaque, with 0.12-20.83% of total PAHs and 0.78-24.76% of total PBDEs added to the microcosm retained in Fe plaque. On the contrary, the percentages of PAHs and PBDEs taken up by plant tissues were relatively small, ranging from not detected to 0.09% and from 0.01 to 2.00%, respectively. More uptake of Fe plaque-immobilized PAHs and PBDEs was found in K. obovata than in E. agallocha, leading to more plant damages in the former species due to its weaker root outer layers. While E. agallocha with stronger root protective outer layer was able to uptake more PAHs and PBDEs from wastewater but immobilize in Fe plaque than that of K. obovata. In both plant species, tidal flushing regimes significantly affected the immobilization of PAHs and PBDEs in Fe plaque, and more frequent tidal flushing led to higher percentages of immobilization. This is the first study demonstrating that E. agallocha was a more suitable mangrove plant species to remove wastewater-borne PAHs and PBDEs than K. obovata, and the significance of tidal flushing on performance of constructed mangrove wetlands.
废水通常含有混合有毒污染物，人工湿地处理系统中植物吸收作用的贡献受到环境条件的影响，特别是潮汐冲刷。在本研究中，调查了两种红树植物，即海漆（Excoecaria agallocha L.）和秋茄（Kandelia obovata Sheue, Liu & Yong）在不同潮汐冲刷条件下对废水中污染物的吸收情况，这些污染物包括多环芳烃（PAHs）和多溴二苯醚（PBDEs）同系物的混合物。结果表明，根表面形成的铁锰氧化物胶膜可以固定废水中的多环芳烃和多溴二苯醚。经过8个月的废水处理后，植物去除的大部分污染物最终都留在了铁锰氧化物胶膜中，添加到微观世界中的总多环芳烃的0.12 - 20.83%和总多溴二苯醚的0.78 - 24.76%保留在铁锰氧化物胶膜中。相反，植物组织吸收的多环芳烃和多溴二苯醚的比例相对较小，分别从未检出到0.09%和0.01%至2.00%。秋茄对铁锰氧化物胶膜固定的多环芳烃和多溴二苯醚的吸收量比海漆多，由于其根外层较弱，导致前者植物受到更多损害。而具有较强根保护外层的海漆能够从废水中吸收更多的多环芳烃和多溴二苯醚，但比秋茄更多地固定在铁锰氧化物胶膜中。在这两种植物中，潮汐冲刷条件显著影响了多环芳烃和多溴二苯醚在铁锰氧化物胶膜中的固定，更频繁的潮汐冲刷导致更高的固定百分比。这是第一项研究表明，与秋茄相比，海漆是一种更适合去除废水中多环芳烃和多溴二苯醚的红树植物，以及潮汐冲刷对人工红树林湿地性能的重要性。
