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Article: Variations of the nitrate isotopic composition in the St. Lawrence River caused by seasonal changes in atmospheric nitrogen inputs

TitleVariations of the nitrate isotopic composition in the St. Lawrence River caused by seasonal changes in atmospheric nitrogen inputs
Authors
KeywordsEutrophication
Time series
Isotope
Nitrogen
Hydrology
St. Lawrence
Issue Date2013
Citation
Biogeochemistry, 2013, v. 115, n. 1-3, p. 287-298 How to Cite?
AbstractWe present 42 dual-isotope nitrate analyses of fresh water samples collected in the St. Lawrence River between June 2006 and July 2008. Measured δ15N-NO3 - and δ18O-NO3 - values correlate negatively, while δ18O-NO3 - displays no negative correlation with nitrate concentration. This suggests that nitrate uptake and/or elimination by denitrification is not the main driver of observed variations in nitrate concentration and isotopic signature in the St. Lawrence River. In addition, δ18O-NO3 - is negatively correlated with the seasonally variable δ18O of ambient water, indicating that the variation in the isotopic signature of nitrate is barely modulated by in-stream nitrate regeneration (nitrification). It rather is constrained by along-river changes in the external sources of nitrate. Given the distinct nitrogen (N) and oxygen (O) isotopic signature of atmospheric nitrate, we argue that observed seasonal variations of δ15N-NO3 - and δ18O-NO3 - in the St. Lawrence River are due to variable contributions of snowmelt-derived water. Based on a N and O isotope mass balance, we show that total nitrate loading in the St. Lawrence River is dominated by a N input from the Great Lakes (47 ± 28 %) and from nitrate regeneration of both internal and external N (48 ± 22 %). While temporal nitrate N and O isotope dynamics in the St. Lawrence River are mainly influenced by the atmospheric N input fluctuations, with an increase in atmospheric loading during spring, atmospheric N plays overall a rather insignificant role with regards to the N budget (5 ± 4 %). © 2013 Springer Science+Business Media Dordrecht.
Persistent Identifierhttp://hdl.handle.net/10722/210581
ISSN
2015 Impact Factor: 3.407
2015 SCImago Journal Rankings: 2.156

 

DC FieldValueLanguage
dc.contributor.authorThibodeau, Benoit-
dc.contributor.authorHélie, Jean François-
dc.contributor.authorLehmann, Moritz F.-
dc.date.accessioned2015-06-19T01:49:27Z-
dc.date.available2015-06-19T01:49:27Z-
dc.date.issued2013-
dc.identifier.citationBiogeochemistry, 2013, v. 115, n. 1-3, p. 287-298-
dc.identifier.issn0168-2563-
dc.identifier.urihttp://hdl.handle.net/10722/210581-
dc.description.abstractWe present 42 dual-isotope nitrate analyses of fresh water samples collected in the St. Lawrence River between June 2006 and July 2008. Measured δ15N-NO3 - and δ18O-NO3 - values correlate negatively, while δ18O-NO3 - displays no negative correlation with nitrate concentration. This suggests that nitrate uptake and/or elimination by denitrification is not the main driver of observed variations in nitrate concentration and isotopic signature in the St. Lawrence River. In addition, δ18O-NO3 - is negatively correlated with the seasonally variable δ18O of ambient water, indicating that the variation in the isotopic signature of nitrate is barely modulated by in-stream nitrate regeneration (nitrification). It rather is constrained by along-river changes in the external sources of nitrate. Given the distinct nitrogen (N) and oxygen (O) isotopic signature of atmospheric nitrate, we argue that observed seasonal variations of δ15N-NO3 - and δ18O-NO3 - in the St. Lawrence River are due to variable contributions of snowmelt-derived water. Based on a N and O isotope mass balance, we show that total nitrate loading in the St. Lawrence River is dominated by a N input from the Great Lakes (47 ± 28 %) and from nitrate regeneration of both internal and external N (48 ± 22 %). While temporal nitrate N and O isotope dynamics in the St. Lawrence River are mainly influenced by the atmospheric N input fluctuations, with an increase in atmospheric loading during spring, atmospheric N plays overall a rather insignificant role with regards to the N budget (5 ± 4 %). © 2013 Springer Science+Business Media Dordrecht.-
dc.languageeng-
dc.relation.ispartofBiogeochemistry-
dc.subjectEutrophication-
dc.subjectTime series-
dc.subjectIsotope-
dc.subjectNitrogen-
dc.subjectHydrology-
dc.subjectSt. Lawrence-
dc.titleVariations of the nitrate isotopic composition in the St. Lawrence River caused by seasonal changes in atmospheric nitrogen inputs-
dc.typeArticle-
dc.description.natureLink_to_subscribed_fulltext-
dc.identifier.doi10.1007/s10533-013-9834-4-
dc.identifier.scopuseid_2-s2.0-84884904563-
dc.identifier.volume115-
dc.identifier.issue1-3-
dc.identifier.spage287-
dc.identifier.epage298-
dc.identifier.eissn1573-515X-

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