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| Titel |
Nutrient budgets for large Chinese estuaries |
| VerfasserIn |
S. M. Liu, G.-H. Hong, J. Zhang, X. W. Ye, X. L. Jiang |
| 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 ; 6, no. 10 ; Nr. 6, no. 10 (2009-10-26), S.2245-2263 |
| Datensatznummer |
250004043
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| Publikation (Nr.) |
 copernicus.org/bg-6-2245-2009.pdf |
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| Zusammenfassung |
| Chinese rivers deliver about 5–10% of global freshwater input and
15–20% of the global continental sediment to the world ocean. We report
the riverine fluxes and concentrations of major nutrients (nitrogen,
phosphorus, and silicon) in the rivers of the contiguous landmass of China
and Korea in the northeast Asia. The rivers are generally enriched with
dissolved inorganic nitrogen (DIN) and depleted in dissolved inorganic
phosphate (PO43−) with very high DIN: PO43−
concentration ratios. DIN, phosphorus, and silicon levels and loads in
rivers are mainly affected by agriculture activities and urbanization,
anthropogenic activities and adsorption on particulates, and rock types,
climate and physical denudation intensity, respectively. Nutrient transports
by rivers in the summer are 3–4 times higher than those in the winter with
the exception of NH4+. The flux of NH4+ is rather
constant throughout the year due to the anthropogenic sources such as the
sewer discharge. As nutrient composition has changed in the rivers,
ecosystems in estuaries and coastal sea have also changed in recent decades.
Among the changes, a shift of limiting nutrients from phosphorus to nitrogen
for phytoplankton production with urbanization is noticeable and in some areas silicon becomes
the limiting nutrient for diatom productivity. A simple steady-state
mass-balance box model was employed to assess nutrient budgets in the
estuaries. The major Chinese estuaries export <15% of nitrogen,
<6% of phosphorus required for phytoplankton production and ~4%
of silicon required for diatom growth in the Chinese Seas (Bohai, Yellow
Sea, East China Sea, South China Sea). This suggests that land-derived
nutrients are largely confined to the immediate estuaries, and ecosystem in
the coastal sea beyond the estuaries is mainly supported by other nutrient
sources such as regeneration, open ocean and atmospheric deposition. |
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