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| Titel |
Aged organic carbon exported from the eastern margin of Tibetan Plateau |
| VerfasserIn |
Jin Wang, Robert Hilton, Zhangdong Jin, Fei Zhang, Alexander Densmore, Darren Gröcke, Xiaomei Xu, Xiaojuan Feng |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144530
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| Publikation (Nr.) |
 EGU/EGU2017-8367.pdf |
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| Zusammenfassung |
| Erosion of particulate organic carbon from the terrestrial biosphere (POCbiosphere) and
sedimentary rocks (POCpetro) plays an important role in the global carbon cycle
across a range of timescales. Knowledge of the age of POCbiosphere is of first order
importance. Discharge of young POCbiosphere (i.e. decades old) by rivers is an export of
recent productivity which is not well captured in ecosystem carbon budgets. Older
POCbiosphere (centuries to millennia in age) can be eroded from deeper soils. If
this aged POCbiosphere is oxidised during river transport, it represents a source of
CO2 to the modern atmosphere. Previous work on the major Himalayan rivers has
identified old POCbiosphere sourced from high elevations in the Tibetan Plateau, yet its
regional significance remains unclear. Here we attempt to quantify the source of POC
and age of POCbiosphere carried by rivers draining the eastern margin of Tibet.
Using suspended sediment samples from 6 river gauging stations in the Min Jiang
from 2005 to 2012, we measured the elemental composition (%OC and %N) and
carbon isotopes (12C, 13C, 14C). In contrast to many other rivers, we find that the
POCpetro is characterized by a large range of stable carbon isotope ratios, ranging from
-26.2‰ to -13.2‰Ṫhis mixes with POCbiosphere and sets the bulk isotopic and elemental
geochemistry. Using the radiocarbon content and an end member mixing model, we
estimate that the age of POCbiosphereranged from modern to over 3000 14C years.
Data from the high elevation tributaries of the Min Jiang support the notion that
aged POCbiosphere is supplied into rivers draining the Tibetan Plateau. The annual
POCbiosphere yields are significant (from 0.2 to 3.1 tC km−2 yr−1) and are set by
the frequency of intense runoff events. Overall, our study highlights the need to
better quantify the age of POCbiosphere in rivers and its fate in the river system. |
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