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| Titel |
Nitrate source identification in the Baltic Sea using its isotopic ratios in combination with a Bayesian isotope mixing model |
| VerfasserIn |
F. Korth, B. Deutsch, C. Frey, C. Moros, M. Voss |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 17 ; Nr. 11, no. 17 (2014-09-15), S.4913-4924 |
| Datensatznummer |
250117593
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| Publikation (Nr.) |
 copernicus.org/bg-11-4913-2014.pdf |
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| Zusammenfassung |
| Nitrate (NO3−) is the major nutrient responsible for coastal
eutrophication worldwide and its production is related to intensive food
production and fossil-fuel combustion. In the Baltic Sea NO3− inputs
have increased 4-fold over recent decades and now remain constantly
high. NO3− source identification is therefore an important
consideration in environmental management strategies. In this study focusing
on the Baltic Sea, we used a method to estimate the proportional
contributions of NO3− from atmospheric deposition, N2 fixation,
and runoff from pristine soils as well as from agricultural land. Our
approach combines data on the dual isotopes of NO3−
(δ15N-NO3− and δ18O-NO3−) in winter
surface waters with a Bayesian isotope mixing model (Stable Isotope Analysis
in R, SIAR). Based on data gathered from 47 sampling locations over the
entire Baltic Sea, the majority of the NO3− in the southern Baltic
was shown to derive from runoff from agricultural land (33–100%),
whereas in the northern Baltic, i.e. the Gulf of Bothnia, NO3−
originates from nitrification in pristine soils (34–100%). Atmospheric
deposition accounts for only a small percentage of NO3− levels in the
Baltic Sea, except for contributions from northern rivers, where the levels
of atmospheric NO3− are higher. An additional important source in the
central Baltic Sea is N2 fixation by diazotrophs, which contributes
49–65% of the overall NO3− pool at this site. The results
obtained with this method are in good agreement with source estimates based
upon δ15N values in sediments and a three-dimensional ecosystem
model, ERGOM. We suggest that this approach can be easily modified to
determine NO3− sources in other marginal seas or larger near-coastal
areas where NO3− is abundant in winter surface waters when
fractionation processes are minor. |
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