Long-term changes in consentrations and flux fo nitrogen in the Mississippi River Basin, USA

Hydrological Processes
By:  and 



Current and historical data show that nitrogen concentrations and flux in the Mississippi River Basin have increased significantly during the past 100 years. Most of the increase observed in the lower Mississippi River has occurred since the early 1970s and is due almost entirely to an increase in nitrate. The current (1980-99) average annual nitrogen (N) flux from the Mississippi Basin to the Gulf of Mexico is about 1 555 500 t year-1, of which about 62% is nitrate-N. The remaining 38% is organic nitrogen and a small amount of ammonium. The current (1980-99) average nitrate flux to the Gulf is almost three times larger than it was during 1955-70. This increased supply of nitrogen to the Gulf is believed to be partly responsible for the increasing size of a large hypoxic zone that develops along the Louisiana-Texas shelf each summer. This zone of oxygen-depleted water has doubled in areal extent since it was first measured in 1985. The increase in annual nitrate flux to the Gulf can be largely explained by three factors: Increased fertilizer use, annual variability in precipitation and increased streamflow, and the year-to-year variability in the amount of nitrogen available in the soil-ground water system for leaching to streams. The predominant source areas for the nitrogen transported to the Gulf of Mexico are basins draining southern Minnesota, Iowa, Illinois, Indiana, and Ohio. Basins in this region yield 1801 to 3050 kg N km-2 year-1 to streams, several times the N yield of basins outside this region.
Publication type Article
Publication Subtype Journal Article
Title Long-term changes in consentrations and flux fo nitrogen in the Mississippi River Basin, USA
Series title Hydrological Processes
DOI 10.1002/hyp.210
Volume 15
Issue 7
Year Published 2001
Language English
Publisher Wiley
Contributing office(s) Toxic Substances Hydrology Program
Description 18 p.
First page 1209
Last page 1226
Google Analytic Metrics Metrics page
Additional publication details