Leaching losses of phosphorus (P) are a potential threat to almost half of the Flemish soil. Recent measurements suggest that phosphorus, faster than expected, migrates through groundwater to surface water and thus, in relatively short time, can pose a major threat to the quality of ground- and surface water. The amount of phosphorus determines the growth of algae in surface waters (eutrophication). In the fertilizer action plan Flanders in consultation with Europe, standards are determined on manure application with respect to P-intake. In the absence of a rapid improvement in water quality with regard to phosphorus, the Commission will take drastic measures. This PhD thesis will focus on field studies to quantify P transport at field and landscape scale in P-saturated basins in Flanders.
The research will focus on the execution and interpretation of flux measurements to estimate P losses from soil to groundwater and surface water. Hereby, different measurement techniques will be applied. To do this, passive sampling techniques will be used including the innovative iFLUX sampler which will then be compared with conventional sampling methods. Research objectives are 1) the validation of a methodology to determine P fluxes across interfaces between soil-groundwater-surface water, 2) the validation of the iFLUX sampler at field sites with different soil type, agricultural practice and hydrological setting; 3) the development of a methodology to calculate field-scale P mass balances to assess (i) the importance of historical sources, (ii) effect of mitigating measures and (iii) relative importance of agricultural sources compared to other emissions for management.