[Phosphorus characteristics and the impact to water quality across interface of overlying water and sediment of Xiazhuhu wetland in Northern Zhejiang Province, China].

Healthy wetland system is regarded as an effective way for biological remediation of non-point source pollutants. A case field investigation on phosphorus (P) status of overlying water and sediment was carried out for Xiazhuhu wetland located in Northern Zhejiang Province, China. A static wetland microcosm experiment was conducted to understand the characteristics and mechanisms related to P exchanging, P forms changing, and water quality impact across the interface of water and sediment. Field investigation showed that total P (TP) concentrations of sediments were found from 0.187 mg x g(-1) to 0.591 mg x g(-1), and TP in overlying water reached from 0.022 mg x L(-1) to 0.718 mg x L(-1) where the seasonal concentration variations of TP, dissolved P (DP), and particulate P (PP) were commonly found in order as winter > summer > spring > fall. Fed by synthetic solution containing P levels of 0.0 - 10.5 mg x L(-1), a 35-day-lasting microcosm study showed that P retention by sediments could be divided into three basic phases in order, i.e., buffer reaction, rapid adsorption, and slow adsorption. Under a typical stress concentration of 1.0 mg x L(-1) in overlying water, the increment of P tanks in different forms was found as NH4 Cl-P (0.0%), Fe-P/Mn-P (around 20%), NaOH-TP (around 66%, mainly as the form of Al-P), Ca-P (1.9%), and Res-P (11.3%), on the condition of Xiazhuhu wetland under low water season. Application of Al to wetland would increase the capacity of sediment P retention in Xiazhuhu wetland.