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Biogeochemistry of organic matter and associated elements along the river-estuary-ocean continuum
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Modeling of riverine dissolved organic carbon (DOC) fluxes in the Changjiang River network: in coupling of in-stream degradation and river hydrology
Wednesday 9th @ 1130-1150, Conference Hall
Weijin Yan* , Institute of Geographical Science and Natural Resources Research, Chinses Academy of Sciences
Lv Shucong, Institute of Geographical Science and Natural Resources Research, Chinses Academy of Sciences
Yu Qibiao, Institute of Geographical Science and Natural Resources Research, Chinses Academy of Sciences
Presenter Email: yanwj@igsnrr.ac.cn |
| Riverine dissolved organic carbon (DOC) is an important carbon pool in the global carbon biogeochemical cycle. DOC export from terrestrial system to marine system via river system can be determined by the DOC input from land to river system and the in-stream removal processes. DOC input from land to rivers depend on the land use or land cover in the watershed. And the DOC in-stream removal primarily involves the biogeochemical and hydrological processes. However, the quantification of its in-stream removal and DOC input from land to rivers are still not sufficiently expounded.
In this study, we examined the relationships between DOC degradation in linking its chemical composition and characteristics in order to obtain an experimental value of DOC in-stream uptake velocity (Vf). Furtherly, by coupling the DOC in-stream uptake velocity and hydrological parameters based on Spiraling theory and river Strahler model, we established a synthesis model to quantify the DOC input from land to rivers (both point source and non-point source), in-stream removal and export through outlet of the basin in the Changjiang River basin according to land use, soil organic matter content, and socio-economic indicators.
Our model predicted that about 4.11 - 7.41 Tg C yr-1 are released from land to rivers and about 1.57 - 2.16 Tg C yr-1 are exported by rivers to sea as DOC with an instream removal proportion of more than 70% at the whole basin scale during 1985-2010, accounting for 0.44% - 0.93% of the global riverine DOC flux. The relative contribution of point source is only about 1.5% - 2.3%. In terms of spatial patterns, the sub-basin of Dongting Lake is the largest contributor to DOC input load from land to rivers. The followings were the sub-basins of Min-Tuo River, the Poyang Lake and the section between Yichang and Jiujiang of the main channel of the Changjiang River. These 4 sub-basins contribute more than 70% of DOC load of the whole river basin. Though there is still great uncertainty regarding DOC in-stream removal, our study provided an improved understanding of the in-stream removal processes of DOC and its flux.
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