Measurement and modelling of phosphorus and nitrogen retention in small constructed wetlands treating agricultural non-point source pollution

azote barrage bassin versant bioremediation cours d'eau cursos de agua dams escorrentia fosforo losses from soil modele modelos models nitrogen nonpoint pollution noruega norway phosphore phosphorus pollution by agriculture pollution diffuse pollution par l'agriculture represas rivers ruissellement runoff sedimentation terre humide watersheds wetlands