鄱阳湖灰化苔草对沉积物-水界面重金属环境行为的影响

With the large-scale exploitation of mineral resources upstream, Poyang Lake water and sediment were polluted by heavy metal, posing a greater threat to the living and manufacturing of residents living in the lake and the downstream. Although there is much research about environmental behavior of the heavy metal in lakes, the mechanism of wetland plants affecting on migration and transformation of heavy metals in the sediment-water interface is not yet discussion in-depth. In this study, Carex cinerascens Kukenth. was chosen as the typical wetland vegetation in Poyang Lake, and its effect on the environmental behavior of heavy metals in water-sediment interface in its entire life cycle was conducted. The fate of heavy metal releasing from Carex cinerascens Kukenth., and the migration, deposition, transformation of heavy metal affected by the variation of environment conditions in the interfaces as well as organic matter of different forms were keep emphasis on the study in the process of Carex cinerascens Kukenth. decomposing. A feedback model between the behavior of heavy metals in the interfaces with the effects aroused by Carex cinerascens Kukenth. decomposing was expected to establish for quantitatively describing the weight of various factors, and revealing the mechanism of the heavy metals behavior in sediment-water interface affected by the entire life cycle of Carex cinerascens Kukenth. The result of the study can be easily imaged to enrich the scientific understanding of migration and transformation mechanism of heavy metals in plants-water-sediment system. Furthermore, the important practical significance in the scientific management of lakes and wetlands resources, reducing the risk of heavy metals contamination of Poyang Lake region and downstream regions also can not be neglected.

针对鄱阳湖水体和沉积物重金属污染日益加剧，对湖区和下游生产、生活造成较大威胁的严峻形势，有必要深入开展湿地植物对重金属在沉积物-水界面环境行为的影响研究。本项目以鄱阳湖最典型的植被类型——灰化苔草为研究对象，在还原灰化苔草生长和腐解生命周期全过程的基础上，分别探讨沉积物-水界面重金属环境行为的响应机制，重点研究灰化苔草腐解过程中植物组织释放的重金属归宿，两相界面环境条件的改变、不同形态有机质释放及其对重金属释放、迁移、沉积与转化的影响，并建立重金属环境行为对灰化苔草腐解的反馈模型，定量描述多种因素的影响权重，揭示鄱阳湖灰化苔草生命周期全过程对沉积物-水界面重金属环境行为的影响机制。项目的开展不仅能丰富科学界对重金属在植物-水-沉积物系统中迁移转化机理的认知，而且对科学管理湖泊湿地资源、降低鄱阳湖区及下游地区水环境重金属的污染风险具有重要的现实意义。

针对鄱阳湖湿地重金属污染日益加剧的严峻形势，有必要深入开展湿地植物对重金属在沉积物-水界面环境行为的影响研究。本研究选取鄱阳湖典型湿地植物灰化苔草，研究了淹水期灰化苔草对沉积物重金属Cu, Zn, Cd, Pb释放的影响、对水体重金属向沉积物沉积的影响、富集了重金属的灰化苔草其体内重金属在水-沉积物界面的分配，并分析了可能的影响机制。.灰化苔草淹水腐解对沉积物重金属释放的影响研究结果显示，在实验进行的135天淹水期内，灰化苔草添加降低了沉积物重金属向上覆水的释放，且植物添加量越多，沉积物重金属释放的量越少。添加7g苔草使上覆水中Cd、Zn浓度可降低达23%，添加17g苔草的处理，上覆水中Cd、Zn浓度可降低达60%；苔草添加对沉积物Cu、Pb释放的降低作用明显高于对Cd、Zn的作用，最高达到90%。实验过程中水体pH没有因为灰化苔草的添加而受到显著影响，同时上覆水体中重金属与溶解性有机碳含量不存在显著正相关关系，结果表明灰化苔草添加对沉积物重金属释放减少的影响与pH和溶解性有机碳含量没有明显相关性。灰化苔草淹水腐解对水体重金属向沉积物沉积的影响研究结果表明，苔草添加处理可明显降低水体中重金属镉含量，促进水体中重金属镉向沉积物迁移。苔草添加处理亦不同程度的降低了水体中重金属含量，最高也达到了百分之九十多。但是两种不同植物的添加量对水体中重金属镉含量降低的影响没有显著差异。富集了重金属的灰化苔草其体内重金属在水-沉积物界面的分配研究结果显示，经过135天的淹水处理，苔草体内富集的重金属仅有百分之十左右进入到上覆水体中，大部分仍存在于沉积物当中，在多数情况下，添加的植物生物量越少，带入到沉积物中的重金属越少，而释放到水体中的重金属反而越多。.本研究不仅在植物对湖泊沉积物-水界面重金属影响的环境行为方面研究具有启发性的科学意义，且对科学管理湖泊湿地资源具有重要的现实意义。