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| Titel |
Speciation and dynamics of dissolved inorganic nitrogen export in the Danshui River, Taiwan |
| VerfasserIn |
T.-Y. Lee, Y.-T. Shih, J.-C. Huang, S.-J. Kao, F.-K. Shiah, K.-K. Liu |
| 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. 19 ; Nr. 11, no. 19 (2014-10-02), S.5307-5321 |
| Datensatznummer |
250117619
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| Publikation (Nr.) |
 copernicus.org/bg-11-5307-2014.pdf |
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| Zusammenfassung |
| Human-induced excess nitrogen outflowing from land through rivers to oceans
has resulted in serious impacts on terrestrial and coastal ecosystems.
Oceania, which occupies < 2.5% of the global land surface, delivers
12% of the freshwater and dissolved materials to the ocean on a global
scale. However, there are few empirical data sets on riverine dissolved
inorganic nitrogen (DIN) fluxes in the region, and their dynamics are poorly
understood. In this study, a river monitoring network covering different
types of land uses and population densities was implemented to investigate
the mechanism of DIN export. The results show that DIN concentration/yield
varied from
∼20 μM/∼300 kg-N km−2 yr−1 to
∼378 μM/∼10 000 kg-N km−2 yr−1
from the relatively pristine headwaters to the populous estuary. Agriculture
and population density control DIN export in less densely populated regions
and urban areas, respectively, and runoff controls DIN at the watershed
scale. Compared to documented estimates from global models, the observed DIN
export from the Danshui River is 2.3 times larger, which results from the
region-specific response of DIN yield to dense population and abundant
runoff. The dominating DIN species change gradually from NO3− in the
headwaters (∼97%) to NH4+ in the estuary
(∼60%) following the urbanization gradient. The prominent
existence of NH4+ is probably the result of the anaerobic water body
and short residence time, unlike in large river basins. Given the analogous
watershed characteristics of the Danshui River to the rivers in Oceania, our
study could serve as a first example to examine riverine DIN fluxes in
Oceania. |
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