Mississippi River nitrate loads from high frequency sensor measurements and regression-based load estimation

Environmental Science & Technology
By: , and 

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Abstract

Accurately quantifying nitrate (NO3) loading from the Mississippi River is important for predicting summer hypoxia in the Gulf of Mexico and targeting nutrient reduction within the basin. Loads have historically been modeled with regression-based techniques, but recent advances with high frequency NO3 sensors allowed us to evaluate model performance relative to measured loads in the lower Mississippi River. Patterns in NO3 concentrations and loads were observed at daily to annual time steps, with considerable variability in concentration-discharge relationships over the two year study. Differences were particularly accentuated during the 2012 drought and 2013 flood, which resulted in anomalously high NO3 concentrations consistent with a large flush of stored NO3 from soil. The comparison between measured loads and modeled loads (LOADEST, Composite Method, WRTDS) showed underestimates of only 3.5% across the entire study period, but much larger differences at shorter time steps. Absolute differences in loads were typically greatest in the spring and early summer critical to Gulf hypoxia formation, with the largest differences (underestimates) for all models during the flood period of 2013. In additional to improving the accuracy and precision of monthly loads, high frequency NO3 measurements offer additional benefits not available with regression-based or other load estimation techniques.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Mississippi River nitrate loads from high frequency sensor measurements and regression-based load estimation
Series title Environmental Science & Technology
DOI 10.1021/es504029c
Volume 48
Issue 21
Year Published 2014
Language English
Publisher American Chemical Society
Contributing office(s) California Water Science Center
Description 8 p.
First page 12612
Last page 12619
Country United States
State Louisiana
County Baton Rouge
Other Geospatial Mississippi River
Online Only (Y/N) N
Additional Online Files (Y/N) N