As the second phase of a large-scale Tulane University Mississippi River wa
ter-qualify database project, nutrient data on the lower Mississippi River
have been examined for potential differences among sampling agencies, geogr
aphic locations and chemically similar nitrogen parameters. These data repr
esent the most comprehensive source of information on nutrients in the Miss
issippi River available as a single database. Monthly means, grouped by par
ameter, sampling location and agency, were calculated and compared as paire
d sets, excluding months where data were not available for both sets. Evalu
ations using ANOVA indicated few differences among agencies providing nitro
gen-compound data, although differences were observed in phosphorus-compoun
d data from different sources. Unfiltered and filtered fractions of nitrate
-nitrite were found to be comparable throughout the study area. Spatial exa
mination of the nutrient data indicated few differences in inorganic nitrog
en concentrations throughout the study area, but significant variability in
total Kjeldahl nitrogen (TKN). Orthophosphate and total phosphorus concent
rations increased through the study area from Arkansas [river miles (RM) 50
0-810] downstream to St. Francisville (RM 231-315), bur with little or no c
hange from Baton Rouge (RM 111-230) to the Gulf of Mexico. Results provide
a combined data set From which preliminary calculations of daily nutrient l
oads in the Mississippi River between 1960 and 1997 were conducted. (C) 199
9 Published by Elsevier Science Ltd. All rights reserved.