沉水植物季节形态变化对底泥再悬浮影响研究

Sediment resuspension is the main source of internal pollution of waterbody, and submerged macrophytes rehabilitation has been demonstrated as one of the effective measures for restoring the eco-environment. There is a complicated ineraction between submerged macrophytes and sediment resuspension, i.e., under different circumstances of planting configurations and flow conditions, the seasonal morphological characteristics of different types of submerged macrophytes may inhibit or enhance sediment resuspension. In fact, the related research is relatively scarce, therefore, it is necessary to explore the relevant law of submerged macrophytes affecting sediment resuspension. In this study, two types (meadows/canopies) of natural submerged macrophytes are selected as experiment objects, and field sediment and submerged macrophytes are collected from natural waterbodies in different growth stage of macrophytes, and then laboratory experiments are carried out. On the basis of field investigation, flume experiments and theoretical analyses, the coupling laws among the seasonal morphological changes of different types of submerged macrophytes and the hydrodynamic characteristics and sediment resuspension will be revealed. The study contents are threefold: 1) the biological morphology and the seasonal changes of submerged macrophytes; 2) the coupling law between hydrodynamic characteristics and the seasonal morphological changes of submerged macrophytes; 3) sediment resuspension laws influenced by seasonal morphological changes of submerged macrophytes. This study will provide scientific supports for pursuing efficient schemes of assessment, design and management of ecological restoration with aquatic macrophytes, moreover, the implementation of this study will enrich the relevant interdisciplinary research.

底泥再悬浮是水体内源污染的主要来源，沉水植物重建是水体生态环境修复的有效手段。沉水植物与底泥再悬浮之间存在复杂的相互影响规律，即不同种植方式及水流条件下，不同类型沉水植物及其季节形态变化特性可能抑制或增强底泥再悬浮程度，相关规律尚有待探求。针对此问题，本项目选取草甸型和冠层型两种类型的天然沉水植物作为研究对象，分别采集不同生长阶段的现场沉水植物及底泥进行水槽试验，基于现场观测、水槽试验和机理分析相结合的研究手段，揭示不同类型沉水植物形态特性演替过程与水流动力特性、底泥再悬浮特性之间的耦合规律。研究内容包括：1）沉水植物基本生物形态及其演变特性；2）沉水植物季节形态变化与水流特性的耦合影响规律；3）沉水植物季节形态变化对底泥再悬浮的影响规律。研究成果可为水生植物生态修复设计与管理提供科学支撑，并能丰富相关学科交叉研究。

底泥再悬浮是水体内源污染的主要来源，沉水植物重建是水体生态环境修复的有效手段。沉水植物与底泥再悬浮之间存在复杂的相互影响规律，即不同种植方式及水流条件下，不同类型沉水植物形态特性可能抑制或增强底泥再悬浮程度，相关规律尚有待探求。针对此问题，本项目基于现场观测、水槽试验和机理分析相结合的研究手段，揭示不同类型沉水植物形态特性与水流动力特性、底泥再悬浮特性之间的耦合规律。基于项目构架，重点研究内容包括：1）沉水植物对水动力特性及底泥再悬浮的影响规律；2）沉水植物横向种植间距对水动力特性及底泥再悬浮的影响规律；3）沉水植物纵向种植间距对水动力特性及底泥再悬浮的影响规律；4）沉水植物物理形态对水动力特性及底泥再悬浮的影响规律。研究成果可为水生植物生态修复设计与管理提供科学支撑，并能丰富相关学科交叉研究。.研究表明，种植沉水植物可明显降低植物顶部以下区域的水体的流速及紊动特性，减小底部切应力，上覆水浊度变化值的测量结果亦表明试验条件下沉水植物可一定程度上抑制底泥再悬浮；横向种植间距对测量垂线水流特性影响明显，横向种植间距越小，植物顶部以下流速减速效应越明显，更有利于减小底部水流紊动效应，降低底泥再悬浮程度；纵向间距对测量垂线水流特性影响不显著，纵向种植间距对底泥再悬浮程度稍有影响；试验冠层型沉水植物沿高度生物量基本一致，在同一种植间距条件下，其底部消流能力和抑制底泥再悬浮能力稍优与试验草甸型沉水植物；初春新发植物低矮，由于水流剪切作用，同样的水流条件下，相较于生物量茂盛的夏季，底泥更易悬浮。