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

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 (k2*, μg(-1) g h(-1)) ranged between 0.007 and 0.017 μg(-1) g h(-1) while, in the case of sediments these ranged between 0.008 and 0.012 μg(-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.