title: Phosphorus losses from agricultural areas in river basins: effects and uncertainties of targeted mitigation measures.
abstract: In this paper we show the quantitative and relative importance of phosphorus (P) losses from agricultural areas within European river basins and demonstrate the importance of P pathways, linking agricultural source areas to surface water at different scales. Agricultural P losses are increasingly important for the P concentration in most European rivers, lakes, and estuaries, even though the quantity of P lost from agricultural areas in European catchments varies at least one order of magnitude (<0.2 kg P ha(-1) to >2.1 kg P ha(-1)). We focus on the importance of P for the implementation of the EU Water Framework Directive and discuss the benefits, uncertainties, and side effects of the different targeted mitigation measures that can be adopted to combat P losses from agricultural areas in river basins. Experimental evidence of the effects of some of the main targeted mitigation measures hitherto implemented is demonstrated, including: (i) soil tillage changes, (ii) treatment of soils near ditches and streams with iron to reduce P transport from source areas to surface waters, (iii) establishment of buffer zones for retaining P from surface runoff, (iv) restoration of river-floodplain systems to allow natural inundation of riparian areas and deposition of P, and (v) inundation of riparian areas with tile drainage water for P retention. Furthermore, we show how river basin managers can map and analyze the extent and importance of P risk areas, exemplified by four catchments differing in size in Norway, Denmark, and the Netherlands. Finally, we discuss the factors and mechanisms that may delay and/or counteract the responses of mitigation measures for combating P losses from agricultural areas when monitored at the catchment scale.
authors.affiliation: National Environmental Research Institute, Department of Freshwater Ecology, Silkeborg, Denmark. BKR@DMU.DK
authors.forename: B
authors.initials: B
authors.lastname: Kronvang
authors.forename: M
authors.initials: M
authors.lastname: Bechmann
authors.forename: H
authors.initials: H
authors.lastname: Lundekvam
authors.forename: H
authors.initials: H
authors.lastname: Behrendt
authors.forename: G H
authors.initials: GH
authors.lastname: Rubaek
authors.forename: O F
authors.initials: OF
authors.lastname: Schoumans
authors.forename: N
authors.initials: N
authors.lastname: Syversen
authors.forename: H E
authors.initials: HE
authors.lastname: Andersen
authors.forename: C C
authors.initials: CC
authors.lastname: Hoffmann
mesh_terms: D000383:Agriculture / Q000379:methods*; D004190:Disasters; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods; D005060:Europe; D007501:Iron; D010758:Phosphorus / Q000378:metabolism*; D010944:Plants; D045483:Rivers; D012987:Soil
chemical_list: D012987:Soil; D010758:Phosphorus; D007501:Iron