Hydrogeochemical processes governing the mobilization of P fractions and spatial distribution of P fractions leading to the variation in nutrient flux from soil to surface waters, will be investigated by conducting the following tasks:
i) Study of soil-soil/water interactions in land draining into western Vansjø is studied on plot scales. Throughfall and soil water from genetic horizons has been monitored along a topographic gradient in two catchments. The relationship between soil pools and P fractions in solution are being assessed in terms of biogeochemical processes governing the mobilization of P in relation to soil characteristics and overall soil water chemistry (WP3). Significance of DNOM to background nutrient load and its governing drivers is assessed.
ii) Mobilization and fluxes of nutrient fractions (WP1) is studied through a regional survey to identify hotspots and preferential hydrological flow-paths governing the mobilization of nutrients from the terrestrial to the aquatic environment by means of End Member Mixing Analysis (WP3, 4).
iii) Process oriented studies of monitoring data from i) is used to identify relationships between environmental pressures and changes to the levels of bio-available nutrient species in the lake. These studies will be used to parameterize and evaluate the influence of different flow paths on loading of nutrient fractions by means the SWAT model (WP3).
iv) Synoptic surveys of discharge and hydrochemistry along the river system during recession episodes will allow validation of model hypotheses (WP3) of transport processes (i, iii) and link between hydrological and chemical outwash processes.