The aim of this study was to investigate the release of inorganic and organic phosphorus species from particles in rivers and estuaries during resuspension events such as storm, wind and tidal induced turbulence. To achieve this aim, laboratory beaker experiments were designed with autoanalyzer 3 (AA3). The study first investigates phosphorus equilibration in ultra-pure water (UHP) water, biotic river water and abiotic river water under short term and long term conditions. Then, three typical organic and inorganic phosphorus compounds were selected (orthophosphate, phytic acid (PTA) and β-D-glucose-6-phosphate monosodium salt (G-6-P)) to simulate the effect of addition input to river and estuaries in the time period of 150 h. The results show that in a turbulent river, dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) will reach equilibrium between the particulate matter and the water column within 24 h. Additional input of DIP or DOP to the river, has different effects to the river nutrients balance. The buffering capacity of the suspended particulate matter (SPM) plays an important role and behavior difference to the inorganic and various organic phosphorus compounds.

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.