Nitrogen flows from European regional watersheds to coastal marine waters

摘要: Executive summary Nature of the problem Most regional watersheds in Europe constitute managed human territories importing large amounts new reactive nitrogen. As a consequence, groundwater, surface freshwater and coastal seawater are undergoing severe nitrogen contamination and/or eutrophication problems. Approaches A comprehensive evaluation net anthropogenic inputs (NANI) through atmospheric deposition, crop N fixation, fertiliser use import food feed has been carried out for all European watersheds. database on N, P Si fluxes delivered at basin outlets assembled. number modelling approaches based either statistical regression analysis or mechanistic description processes involved transfer transformations have developed relating to outputs into marine ecosystems. Key findings/state knowledge Throughout Europe, NANI represents 3700 kgN/km²/yr (range, 0–8400 depending watershed), i.e. five times background rate natural 2 fixation. mean approximately 78% does not reach outlet, but instead is stored (in soils, sediments ground water) eliminated atmosphere as forms . delivery zone totals 810 200–4000 about four background. In areas limited availability silica, these cause harmful algal blooms.