【摘要】 研究湿地底泥污染特性及水-土界面边界层性质是明确大型人工湿地长期运行下底泥内源污染问题的关键.本文以典型人工湿地为例,通过综合布点垂向分层监测湿地底泥理化性质,明确底泥污染特性,分析水-土界面边界氧化层现象、性质及形成机理,探讨其性质成因.结果表明:与湖泊类似,长期运行人工湿地底泥也会产生氧化层,垂向由上到下分为氧化层、污染层、过渡层和健康层;运行6年的湿地底泥可形成厚约1 cm、无明显臭味、棕黄色可塑状的氧化层;与污染层相比,氧化层色味变淡、流动性减弱,含水率、d(0.9)、亚铁、总有机碳和总氮含量分别降低7.20%、54.04%、54.59%、17.89%和7.00%,氧化还原电位和总磷含量分别升高150.41%和18.17%;氧化层是由氧化、沉降协同作用下形成的底泥表层氧化态微环境,其中上覆水溶解氧水平越高越有利于提高氧化层致密程度,降低氧化层有机质、总氮含量,上覆水悬浮物浓度越高、水深越深越有利于增加氧化层厚度.更多还原

【Abstract】 The study on the characteristics of sediment pollution and the boundary layer of water-soil interface is the key to identify the problem of sediment pollution under the long-term operation of large constructed wetlands. This paper takes a typical surface flow constructed wetland as an example,through comprehensive vertical layered monitoring of the physicochemical properties of the wetland sediment,to clarify the pollution characteristics of the sediment and analyzed the phenomenon,nature and formation mechanism of the boundary oxidation layer of the water-soil interface. The results show that,similar to lakes,the sediment of constructed wetland in long-term operation also generates oxidation layer,which is divided into oxidation layer,pollution layer,transition layer and health layer from top to bottom. After 6 years of operation,the wetland sediment can form an oxidation layer,which is about 1 cm thick,brown-yellow,malleable,with no obvious odor. Compared with the pollution layer,the color and smell of the oxidation layer are weakened,and its fluidity is weakened. Meanwhile,the water content,d( 0.9),diatomic iron,total organic carbon and total nitrogen are decreased by 7. 20%,54. 04%,54. 59%,17. 89% and 7. 00%. Eh and total phosphorus are increased by150.41% and 18.17%,respectively. Oxidation layer is a micro-environment of surface oxidation state formed under the synergistic action of oxidation and settlement. The higher the dissolved oxygen level of overlying water is,the more favorable it is to increase the density of the oxidation layer and reduce the organic matter and total nitrogen content of the oxidation layer. In addition,the higher the concentration of overlying water suspended substance and the deeper the water depth,the more favorable it is to increase the thickness of the oxidation layer.更多还原