Effect of Turbulence on Phosphorus Release from Estuarine Sediment

Abstract

Phosphorus (P) is an essential element for growth in aquatic ecosystems but the dynamics of phosphorus cycling within catchments is poorly constrained. The aim of this study was therefore to develop analytical tools to investigate the release of inorganic and organic phosphorus species in rivers and estuaries during resuspension events such as storm, wind and tidal induced turbulence. To achieve this aim, laboratory simulations using a mini-annular flume coupled with segmented flow analyser detection were performed. To collect SPM (suspended particulate matter), a specially designed specimen box was deployed in the River Tamar (Devon, UK). Inorganic and total phosphorus were determined using segmented flow analyser methods adapted for use with acidified persulfate digests. The segmented flow analyser had a detection limit (3 s.d.) of 0.53 µg P L −1 for inorganic P and 1.5 µg P L −1 for total P. The mini-annular flume provides a suitable method for laboratory simulations, e.g. we managed to get low blanks and good experimental reproducibility, and are also able to see changes in P species within analytical precision. Results showed that increase of shear stress (or SPM) caused release of inorganic P from sediment. This could be used as a fact to build a model to study P dynamics during resuspension events in the river and estuaries environment.