Nitrogen and phosphorus in the subtropical Presidio River, northwestern Mexico

The aim of this study was to assess its nitrogen and phosphorus concentrations in the Presidio River, because it receives large volumes of wastewater with high loads of detergents and fertilizers. The mean concentrations of total nitrogen and phosphorus determined between February 2008 and January 2009 were 640 and 167 [micro]g [L.sup.-1], respectively. The permissible phosphorous concentration established by the Official Mexican Standard NOM-001-SEMARNAT-1996 for pollutants discharge into rivers is 5000 [micro]g [L.sup.-1]. However, according to international standards on phosphorous concentrations in continental water b27odies, the Presidio River may be considered hypereutrophic.