DOI: 10.25976/bu80-h462
title: South Saskatchewan River Basin nitrate source isotope tracing

description: This research project sampled 17 mainstem sites of the Bow River and Oldman River, part of the South Saskatchewan River basin in Alberta, during high and low discharge periods in 2014 and 2015. Riverine nitrate and boron concentrations, mean daily flux, major ion chemistry, and stable isotope measurements of nitrogen-15 of nitrate, oxygen-18 of nitrate, and boron-11 of dissolved boron were determined and compared against results for effluent from seven local wastewater treatment plants (WWTPs), eight synthetic fertilizers, cow manure, and three predominantly agricultural tributary sites to estimate point and non-point nitrate sources using a combined isotope tracing approach. Only river mainstem and tributary chemistry is included in this dataset, please contact the data steward for more data including point and non-point sources. The results of the study indicated WWTP effluent was the key nutrient source in the Bow River downstream of Calgary and manure-derived nutrients affect the Bow and Oldman Rivers in agricultural regions. Overall, boron was proven to be an effective co-tracer for discriminating between urban and agricultural sources of nitrate in a large, mixed-use watershed. 

We would like to acknowledge co-authors Dr. Bernhard Mayer and Michael Nightingale of the University of Calgary Applied Geochemistry Group and Dr. Patrick Laceby of Alberta Environment and Protected Areas for their significant contributions to this research. We are grateful to Steve Taylor, Jesusa Pontoy, Andrew Kingston, Kerri Miller, and Michael Wieser who provided laboratory analysis expertise and assistance. We would also like to thank Veronique Lajciak (Fau) and Nadine Taube who assisted with field logistics and collection of water samples. This study was supported by a NSERC Discovery Grant awarded to Bernhard Mayer.
description: Grab samples were collected during both high and low discharge periods with a total of four sampling campaigns in the Bow River (June 2014, September 2014, June 2015 and September
2015) and three in the Oldman River including all tributary sites (October 2014, June 2015 and October 2015). High discharge periods in these mountain-fed rivers typically occur in June, and low flow periods between September and October. The low discharge grab samples for the Oldman River were obtained after the irrigation return-flow canals were drained back into the mainstem, prior to the winter season.

Surface water grab samples were collected from shore using a sampling pole to reach a point in the river where flow was steady and a thorough mixing of solutes was assumed. Temperature, pH and electrical conductivity were measured in-stream at each sampling site using an Orion 4 Star portable pH meter (Thermo Scientific) and a Russell RL060C portable conductivity meter (Thermo ElectronCorporation). At each site between 0.5 and 2.0 L of water was collected and filtered using a Nalgene hand-pump filtration device with 0.45 mm nitrocellulose filters. Samples were stored in polyethylene Nalgene bottles and maintained at 4 degrees C in cooled containers until they were returned to the laboratory and either processed within 72 h or refrigerated. For anion concentration and isotope analysis samples were frozen upon return to the laboratory until analysis. For cation concentration analysis samples were acidified to a pH &lt; 2 with Omnitrace concentrated nitric acid.