Department of Water Science and Engineering (WSE), IHE Delft Institute for Water Education, Westvest 7, P. O. Box 3015, 2601DA, Delft, the Netherlands.
Department of Water Science and Engineering (WSE), IHE Delft Institute for Water Education, Westvest 7, P. O. Box 3015, 2601DA, Delft, the Netherlands; Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, 6700AA Wageningen, the Netherlands.
J Environ Manage. 2019 Apr 15;236:510-518. doi: 10.1016/j.jenvman.2019.02.016. Epub 2019 Feb 13.
There is critical concern over heavy metals because they are biotoxins. The best management option is elimination or at least minimization of effluence into the environment, but in several regions, mining wastewater or acid mine drainage (AMD) effluence into natural wetlands has continued. The ability of wetlands to attenuate heavy metals in mining wastewater and AMD has led to natural wetlands being used as recipients of these effluents in many parts of the world. Ten greenhouse-based laboratory-scale constructed wetlands (GLCW) were set up at IHE-Delft Institute for Water Education to understand the mechanisms and fate of heavy metals in three Zambian wetlands in attenuation of Co, Cu, and Pb. These were operated as Free Water Surface Constructed Wetlands (FWS-CWs). The principal investigations compared how vegetated and unvegetated microcosm artificial wetlands retained controlled additions of heavy metals and the effect of drying and rewetting on that. The potential for phytoremediation using Typha angustifolia was also investigated. Typha angustifolia was planted in three vegetated and compared with one unvegetated treatment. Treatments A, B, and, the investigated, Treatment D received synthetic wastewater containing Co, Cu, and Pb, while a control, Treatment C, received tap water. Water samples were taken throughout the experiment, and sediment samples collected after the first flushing and before drying. Samples of T. angustifolia were taken before drying the wetlands. Analyses for Co, Cu, and Pb were made in the water and sediment, and in roots, stems and leaves of plant samples. The unvegetated Dutch sediments GLCWs removed more Co from wastewater (52%) than the vegetated Dutch and Zambian sediments GLCWs (13% and -4%, respectively). There was a similar removal of Cu among the GLCWs receiving wastewater (81%-87%). The removal of Pb was significantly higher in the vegetated Dutch sediment GLCWs than the unvegetated Dutch sediments GLCWs, (89% and 72%, respectively). It was concluded that a hectare of the vegetated Zambian sediments with similar design parameters of 50 mg/m.day for Co, Cu, and Pb used in the experiment would on average retain 83 g/day of Co, and 417 g/day of both Cu and Pb. After drying, Co, Cu, and Pb washed out on the first day of rewetting. The washout after that took only a few days. How long the metals washed out of the GLCWs was in order Co > Cu > Pb. T. angustifolia could neither be classified as an accumulator nor an excluder species because the concentrations of Co, Cu, and Pb in the sediments and T. angustifolia were below phytotoxic levels mainly due to a short running period of the experiment.
人们对重金属非常关注，因为它们是生物毒素。最佳管理选择是消除或至少将流出物最小化到环境中，但在一些地区，矿山废水或酸性矿山排水 (AMD) 仍持续流入自然湿地。湿地在减轻矿山废水中重金属和 AMD 方面的能力导致自然湿地在世界许多地区被用作这些流出物的接受者。为了了解三种赞比亚湿地在 Co、Cu 和 Pb 衰减方面重金属的机制和归宿，IHE-Delft 水利教育学院设立了 10 个基于温室的实验室规模人工湿地 (GLCW)。这些湿地被用作自由水面人工湿地 (FWS-CWs)。主要研究比较了植被和无植被微宇宙人工湿地如何保留受控添加的重金属，以及干燥和重新润湿对其的影响。还研究了利用香蒲 (Typha angustifolia) 进行植物修复的潜力。在三个植被处理中种植了香蒲，并与一个无植被处理进行了比较。处理 A、B 和 D 接收含有 Co、Cu 和 Pb 的合成废水，而对照处理 C 接收自来水。整个实验过程中采集水样，第一次冲洗前和干燥前采集沉积物样品。在湿地干燥之前采集香蒲样品。对水样和沉积物以及植物样品的根、茎和叶中的 Co、Cu 和 Pb 进行了分析。无植被的荷兰沉积物 GLCW 从废水中去除的 Co 比植被的荷兰和赞比亚沉积物 GLCW 多（分别为 52%、13%和-4%）。接收废水的 GLCW 对 Cu 的去除率相似（81%-87%）。在植被荷兰沉积物 GLCW 中 Pb 的去除率明显高于无植被荷兰沉积物 GLCW（分别为 89%和 72%）。结论是，一公顷具有类似设计参数的赞比亚植被沉积物，每天用于 Co、Cu 和 Pb 的 50mg/m.day，平均每天可保留 83g Co，以及 417g Cu 和 Pb。干燥后，Co、Cu 和 Pb 在重新润湿的第一天就被冲出。之后几天就冲完了。从 GLCW 中冲洗出来的金属的时间顺序是 Co>Cu>Pb。香蒲既不能被归类为积累者，也不能被归类为排斥者，因为 Co、Cu 和 Pb 在沉积物和香蒲中的浓度低于植物毒性水平，主要是由于实验运行时间较短。
