Tracing nitrate sources with a combined isotope approach (δ15NNO3, δ18ONO3 and δ11B) in a large mixed-use watershed in southern Alberta, Canada

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dc.contributor.authorKruk, M.K.
dc.contributor.authorMayer, B.
dc.contributor.authorNightingale, M.
dc.contributor.authorLaceby, J.P.
dc.date.accessioned2023-03-18T02:45:36Z
dc.date.available2023-03-18T02:45:36Z
dc.date.issued2020-01
dc.description.abstractRapid population growth and land-use intensification over the last century have resulted in a substantial increase in nutrient loads degrading marine and freshwater ecosystems worldwide. In mixed-use watersheds, elevated nitrogen loads from wastewater treatment plant (WWTP) effluent or agricultural runoff often drive the eutrophication of waterways. Accordingly, the objective of this research was to identify sources of riverine nitrate (NO3), a deleterious dissolved species of nitrogen, with a combined isotopic tracing technique in the Bow River and the Oldman River in Alberta, Canada. Riverine NO3 and boron (B) concentrations, mean daily flux and δ15NNO3, δ18ONO3, and δ11B values were determined at 17 mainstem sites during high and low discharge periods in 2014 and 2015. The data for mainstem sites were then compared to results for effluent from seven WWTPs, eight synthetic fertilizers, cow manure, and three predominantly agricultural tributary sites to estimate point and non-point NO3 sources. The NO3 flux, δ15NNO3 and δ18ONO3 values indicated the city of Calgary’s Bonnybrook WWTP effluent accounts for the majority of the NO3 flux in the Bow River downstream of Calgary. δ15NNO3 and δ11B values in the Bow River highlighted an increase in agricultural NO3 loading downstream of irrigation return-flows. A three-fold decrease in the NO3:B flux ratio indicated NO3-removal processes are active in the lower reaches of the Bow River. For the Oldman River, δ11B values revealed elevated nutrient loading from the Lethbridge WWTP effluent (10% of downstream B flux). Furthermore, the agricultural tributaries contributed 25% of the local B flux to the Oldman River. Overall, δ11B was proven to be an effective co-tracer for discriminating between urban and agricultural sources of NO3 in these large mixed-use watersheds. This combined isotope tracing approach has significant potential to identify point and non-point NO3 sources driving eutrophication around the world.en_US
dc.identifier.citationKruk, M. K., Mayer, B., Nightingale, M., & Laceby, J. P. (2020). Tracing nitrate sources with a combined isotope approach (δ15NNO3, δ18ONO3 and δ11B) in a large mixed-use watershed in southern Alberta, Canada. Science of The Total Environment, 703, 135043. https://doi.org/10.1016/j.scitotenv.2019.135043en_US
dc.identifier.doihttp://dx.doi.org/10.1016/j.scitotenv.2019.135043en_US
dc.identifier.urihttp://hdl.handle.net/1880/115932
dc.identifier.urihttps://doi.org/10.11575/PRISM/46081
dc.language.isoengen_US
dc.publisherElsevieren_US
dc.publisher.departmentGeoscienceen_US
dc.publisher.facultyScienceen_US
dc.publisher.hasversionacceptedVersionen_US
dc.publisher.institutionUniversity of Calgaryen_US
dc.publisher.policyhttps://www.elsevier.com/journals/science-of-the-total-environment/0048-9697/open-access-optionsen_US
dc.rightsUnless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.en_US
dc.subjectBoron isotopesen_US
dc.subjectNitrate isotopesen_US
dc.subjectNutrientsen_US
dc.subjectWastewateren_US
dc.subjectUrbanen_US
dc.subjectAgricultureen_US
dc.titleTracing nitrate sources with a combined isotope approach (δ15NNO3, δ18ONO3 and δ11B) in a large mixed-use watershed in southern Alberta, Canadaen_US
dc.typejournal articleen_US
ucalgary.item.requestcopyfalseen_US
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