High-Resolution Profiles of Dissolved Reactive Phosphorus in the Porewaters of Lake Sediments Assessed by DGT Technique

Jian Wang,Jingtian Zhang,Fengyu Zan,Shouliang Huo,Qiong Xie,Shengpeng Zuo

doi:10.4236/jep.2014.58070

Abstract

The technique of DGT (diffusive gradients in thin films) was applied to obtain high-resolution vertical profiles of dissolved reactive phosphorus (DRP) in sediment porewater of Lake Chaohu, a shallow eutrophication lake. Three kinds of DGT probes (with three thicknesses of diffusive gel: 0.38 mm, 0.78 mm and 1.18 mm) measured vertical concentration and induced flux from solid to solution phase which had intricate variations with depth. The results indicated that higher concentrations and induced fluxes of DRP were achieved by using DGT probe with thicker diffusion layer (CDGT1.18 > CDGT0.78 > CDGT0.38) and relatively stable DRP concentration profiles using DGT probes with 0.78 mm diffusive gel were obtained in each sediment core. The DRP concentrations displayed a clear gradient from Core C1 to Core C3 in sediment porewaters due to different sources and exchange degrees of reactive phosphorus. Compared to the concentrations obtained by the centrifugation technique, the concentrations of DRP resulting from the DGT technique were higher because some dissolved reactive phosphorus compounds have always been neglected using conventional centrifugation method.

Highlights

Sediments have received large amounts of phosphorus, including inorganic species and organic species (e.g. DNA-P, P-lipids, Teichoic-P) [1] [2]
The trend of Dissolved reactive phosphorus (DRP) concentrations in the profile was the same as average DRP concentration determined by diffusive gradient in thin films (DGT) with different diffusive gel thickness, which indicated relatively higher phosphorus transferred from solid phrase of sediment to porewater in the profile using DGT with thicker diffusive gel
The higher concentrations and induced fluxes of DRP from sediments to porewaters were obtained with thicker diffusive gel and DGT probes with 0.78 mm diffusive gel were stable and more appropriate for DRP measurement in sediment porewaters

Summary

Introduction

Sediments have received large amounts of phosphorus, including inorganic species (e.g. mono- or diprotonated orthophosphate) and organic species (e.g. DNA-P, P-lipids, Teichoic-P) [1] [2]. Dissolved reactive phosphorus (DRP) is the predominant inorganic species which is bioavailable for algae and other phytoplankton according to its abundance and dynamics [1]. Some inorganic condensed phosphorus (e.g. pyrophosphate, tripolyphosphate, trimetaphosphate) may pass a 0.45 μm filter which is bioavailable for algae [7]. The diffusive gradient in thin films (DGT) technique is an in situ analytical method that is designed to accumulate labile species (e.g. metals, sulfide, phosphorus) in environmental systems [7] [9] [10]. DGT in situ accumulates these species on a binding gel after they freely transport through a diffusive layer and 0.45 μm filter membrane. More than 95% recovery and high capacities were obtained for these labile species determination using DGT [11] [12]

Methods

Results

Conclusion