Using paired in situ high frequency nitrate measurements to better understand controls on nitrate concentrations and estimate nitrification rates in a wastewater-impacted river

Water Resources Research
By: , and 

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Abstract

We used paired continuous nitrate ( math formula) measurements along a tidally affected river receiving wastewater discharge rich in ammonium ( math formula) to quantify rates of change in math formula concentration ( math formula) and estimate nitrification rates. math formula sensors were deployed 30 km apart in the Sacramento River, California (USA), with the upstream station located immediately above the regional wastewater treatment plant (WWTP). We used a travel time model to track water transit between the stations and estimated math formula every 15 min (October 2013 to September 2014). Changes in math formulaconcentration were strongly related to water temperature. In the presence of wastewater, math formulawas generally positive, ranging from about 7 µM d−1 in the summer to near zero in the winter. Numerous periods when the WWTP halted discharge allowed the math formula to be estimated under no-effluent conditions and revealed that in the absence of effluent, net gains in math formula were substantially lower but still positive in the summer and negative (net sink) in the winter. Nitrification rates of effluent-derived NH4 ( math formula) were estimated from the difference between math formula measured in the presence versus absence of effluent and ranged from 1.5 to 3.4 µM d−1, which is within literature values but tenfold greater than recently reported for this region. math formula was generally lower in winter (∼2 µM d−1) than summer (∼3 µM d−1). This in situ, high frequency approach provides advantages over traditional discrete sampling, incubation, and tracer methods and allows measurements to be made over broad areas for extended periods of time. Incorporating this approach into environmental monitoring programs can facilitate our ability to protect and manage aquatic systems.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Using paired in situ high frequency nitrate measurements to better understand controls on nitrate concentrations and estimate nitrification rates in a wastewater-impacted river
Series title Water Resources Research
DOI 10.1002/2017WR020670
Volume 53
Issue 10
Year Published 2017
Language English
Publisher AGU
Contributing office(s) California Water Science Center
Description 20 p.
First page 8423
Last page 8442
Country United States
State California
Other Geospatial Sacramento River