Kinetics of the PO4-P adsorption onto soils and sediments from the Mondego estuary (Portugal)

Abstract

In order to assess the status of a North Atlantic Ocean Ecoregion (Mondego system, Portugal) after the implementation of a management programme, a study on PO4-P sorption was carried out. Considering that sorption velocity markedly determines the systems promptness to phosphorus external loading, the kinetics of the sorption of PO4-P onto estuarine sediments and the upstream agricultural soils was studied. The pseudo-second order kinetic equation gave an appropriate description of PO4-P sorption onto these soils and sediments, allowing for a quantitative comparison. For soils, the kinetic constants (k 2, lg 1 g h 1) ranged between 0.007 and 0.017 lg 1 g h 1 while, in the case of sediments these ranged between 0.008 and 0.012 lg 1 g h 1. Results showed that the reduction of water residence time after the management action was relevant for the system status, affecting its reaction capacity to phosphorus loading.The authors want to acknowledge financial support from FCT (Fundação para a Ciência e a Tecnologia) to CESAM (Centre for Environmental and Marine Studies) and to IMAR (Institute of Marine Research). The Post-Doc grant SFRH/BPD/48449/2008 (P. Coelho) funded by FCT is also acknowledged