黄河口典型芦苇湿地土壤磷的吸附动力学特征

Adsorption kinetics of phosphorus on typical wetland soils with Phragmites australis in the Yellow River Estuary

以黄河口不同淹水条件的芦苇湿地为研究对象(潮汐淹水湿地、淡水恢复湿地和季节性淹水湿地),通过吸附模拟实验探讨了不同类型湿地表层土壤对磷的吸附动力学特征及其影响因素,评估了不同淹水条件下湿地土壤对磷的吸附能力。研究结果表明:具有不同水盐条件的芦苇湿地土壤对上覆水体中磷的吸附表现为淡水恢复湿地>潮汐淹水湿地>季节性淹水湿地,淡水恢复湿地土壤对磷的吸附量最大;三类湿地土壤对磷的吸附过程均表现为初期(0~3 h)最快、中期(3~24 h)逐渐减慢、后期(24 h以后)慢而平衡的状态,但淡水恢复湿地土壤对磷的吸附速率最快,季节性淹水湿地土壤对磷的吸附速率最慢且存在着时间上的延迟性;三类湿地土壤的水盐条件和理化性质差异(如pH、盐度、土壤质地、Al0、Fe0和Ca0)是导致三类湿地土壤对磷的吸附量和吸附速率存在差异的主要因素;Simple Elovich模型和Power Function模型更适合模拟黄河口芦苇(Phragmites australis)湿地土壤对磷的吸附动力学特征。在黄河口退化芦苇湿地实施淡水恢复工程,能够在一定程度上促进湿地土壤对磷的吸附,进而降低湿地水体发生富营养化的风险。

Phragmites auatralis wetlands affected by different flooding conditions(TW:tidal flooding wetlands;FW:fresh water restoration wetland;SW:seasonal flooding wetlands)were selected in the Yellow River Estuary to analyze the adsorption kinetics characteristics and influencing factors of phosphorus on surface wetland soils.Our results suggested that the adsorption of phosphorus in the overlying water on reed wetland soils with different water and salt conditions showed an order of FW>TW>SW,which indicated that the phosphorus adsorption capacity of FW soils was the largest.The phosphorus adsorption of soils from these three types of wetlands exhibited the fastest initial stage(0-3 h),and then gradual slowing(3-24 h),after that a slow and balanced state(after 24 h).However,the FW soils had the fastest absorption rate to phosphorus,while the SW soils showed the slowest absorption rate.The difference in water and salt conditions and physicochemical properties of wetland soils(such as pH,salinity,soil texture,Al0,Fe0 and Ca0)were the main factors leading to differences in phosphorus adsorption amount and rate among the three types of wetland soils.The Simple Elovich model and the Power Function model were more suitable to simulate the dynamic characteristics of phosphorus adsorption by Phragmites auatralis wetland soils in the Yellow River Estuary.The freshwater restoration project of degraded wetlands in the Yellow River Estuary can promote the adsorption of phosphorus on wetland soils to a certain extent,and thus reduce the eutrophic risk of the overlaying water of coastal wetlands.