Nitrate concentration and flux were estimated from 1980 through 2010 at eight sites in the Mississippi River Basin as part of the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS). These estimates extend the results fr
Murphy, Jennifer C. jmurphy@usgs.gov,Hirsch, Robert M. rhirsch@usgs.gov,Sprague, Lori A. lsprague@usgs.gov. Nitrate in the Mississippi River and its tributaries, 1980-2010: an update. 2013-01-01.