title: Global Gray Water Footprint and Water Pollution Levels Related to Anthropogenic Nitrogen Loads to Fresh Water.
abstract: This is the first global assessment of nitrogen-related water pollution in river basins with a specification of the pollution by economic sector, and by crop for the agricultural sector. At a spatial resolution of 5 by 5 arc minute, we estimate anthropogenic nitrogen (N) loads to freshwater, calculate the resultant gray water footprints (GWFs), and relate the GWFs per river basin to runoff to calculate the N-related water pollution level (WPL) per catchment. The accumulated global GWF related to anthropogenic N loads in the period 2002-2010 was 13×10(12) m3/y. China contributed about 45% to the global total. Three quarters of the GWF related to N loads came from diffuse sources (agriculture), 23% from domestic point sources and 2% from industrial point sources. Among the crops, production of cereals had the largest contribution to the N-related GWF (18%), followed by vegetables (15%) and oil crops (11%). The river basins with WPL>1 (where the N load exceeds the basin's assimilation capacity), cover about 17% of the global land area, contribute about 9% of the global river discharge, and provide residence to 48% of the global population.
authors.affiliation: Twente Water Centre, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Mesfin M
authors.initials: MM
authors.lastname: Mekonnen
authors.affiliation: Twente Water Centre, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Arjen Y
authors.initials: AY
authors.lastname: Hoekstra
mesh_terms: D000383:Agriculture; D002681:China; D018556:Crops, Agricultural; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis*; D045483:Rivers; D014874:Water Pollutants, Chemical / Q000032:analysis; D014876:Water Pollution / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D009584:Nitrogen