表流湖滨湿地磷素汇-源功能研究

对抚仙湖马料河湖滨湿地基质进行了室内静态模拟,计算了基质-水界面磷平衡浓度(EPCo),确定湿地基质是充当溶解性活性磷(SRP)的源项或是汇项功能.此外,结合野外监测试验,即在静态实验期间对湿地进出口处水体的SRP浓度及流量进行了连续测定,对静态实验结果进行了验证.野外监测结果表明,基质是作为SRP源项还是汇项,在很大程度上取决于进水流量及进水磷浓度.在暴雨情况下,由于雨水的稀释作用,出水SRP浓度低于进水浓度;当进水量较小时,则取决于进水SRP浓度.进水SRP浓度高于磷平衡浓度,即作为汇项;进水SRP浓度低于磷平衡浓度,即作为源项.用一个简单的模型预测了基质-水界面系统的相互作用及SRP转换过程.该模型中假设基质表层以上10cm为水-土界面层,SRP释放或吸附均在这个边界层进行.预测结果表明,基质-水完全混合时,基质无论是吸附或释放磷速率都很大,大部分SRP通量迁移转换都在1h之内完成;界面系统基质磷释放/吸附主要受控于基质-水界面处EPCo和上覆水SRP浓度梯度.

Phosphorus sink-source function of a lakeside surface flow wetland

Laboratory experiments under static conditions were performed on the sediment of a lakeside wetland,the Maliaohe river wetland of Fuxianhu lake,to investigate the Equilibrium Phosphorus Concentration(EPC0) of the sediment-water interface.The EPC0 is used as an indicator of the source or sink function of the sediment for soluble reactive phosphorus(SRP).In-situ observations of SRP and flow rate were also carried out for the Maliaohe river wetland to verify the laboratory experiments.The field observations showed that the function of the sediment as a source or sink for SRP depends mainly on the flow rate and the phosphorus concentration of the wetland inflow.During storms,the SRP concentration of the effluent is lower than that of the influent due to dilution by rainwater.When the flow rate is low,the SRP concentration of the influent plays an important role in determining the function of the sediment.When the SRP concentration of the influent is greater than the EPC0,the sediment functions as a sink for phosphorus,but otherwise it functions as a source.A simple mathematical model was used to estimate the interaction between the sediment and the overlying water column and the SRP flux across the sediment-water interface.In the model,the sediment-water interface was assumed to be the top 10 cm of the sediment,and processes of SRP adsorption and release were assumed to occur within this layer.The model showed that the rates of adsorption and release of SRP by the sediment were quite high when the water and the sediment were in a complete mixing condition.A large proportion of the SRP flux across the interface occurs within the first one hour.The adsorption or release of SRP by the sediment is mainly subject to the EPC0 and the concentration gradient of the SRP of the influent.