Export of nitrogen from catchments: A worldwide analysis

9 pages, 4 figures.-- PMID: 18374463 [PubMed].-- Printed version published on Nov. 2008.-- Supplementary data available: Tables: Data sources of nitrogen export by world catchments and catchment characterization.This study reviews nitrogen export rates from 946 rivers of the world to determine the influence of quantitative (runoff, rainfall, inhabitant density, catchment area, percentage of land use cover, airborne deposition, fertilizer input) and qualitative (dominant type of forest, occurrence of stagnant waterbodies, dominant land use, occurrence of point sources, runoff type) environmental factors on nitrogen fluxes. All fractions (total, nitrate, ammonia, dissolved organic and particulate organic) of nitrogen export showed a left-skewed distribution, which suggests a relatively pristine condition for most systems. Total nitrogen export showed the highest variability whereas total organic nitrogen export comprised the dominant fraction of export. Nitrogen export rates were only weakly explained by our qualitative and quantitative environmental variables. Our study suggests that the consideration of spatial and temporal scales is important for predicting nitrogen export rates using simple and easy-to-get environmental variables. Regionally based modelling approaches prove more useful than global-scale analyses.Spatial and temporal scales are important determinants for nitrogen export from catchments and emphasis should be put on regional approaches.This is a result of Project CGL2006-2346-HID, funded by the Spanish Ministry of Education.Peer reviewe