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The sources and seasonal fluxes of particulate organic carbon in the Yellow River |
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| Authors: | Yuanxin Qu Zhangdong Jin Jin Wang Yunqiang Wang Jun Xiao Long-Fei Gou Fei Zhang Chun-Yao Liu Yongli Gao Marina B Suarez Xiaomei Xu |
| Institution: | 1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China;2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China
CAS Center for Excellence in Quaternary Science and Global Change, Xi'an, China;3. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China CAS Center for Excellence in Quaternary Science and Global Change, Xi'an, China Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an, China;4. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China University of Chinese Academy of Sciences, Beijing, China;5. Department of Geological Sciences, Center for Water Research, University of Texas at San Antonio, San Antonio, TX, USA;6. Department of Geological Sciences, University of Texas at San Antonio, San Antonio, TX, USA Current address: Department of Geology, The University of Kansas, Lawrence, KS 66045, USA;7. Department of Earth System Science, University of California, Irvine, Irvine, CA, USA |
| Abstract: | The Yellow River transports a large amount of sediment and particulate organic carbon (POC), which is thought to mainly derive from erosion of the Chinese Loess Plateau (CLP). However, the compositions, sources and erosional fluxes of POC in the Yellow River remain poorly constrained. Here we combined measurements of mineralogy, total organic carbon content (OCtotal), stable organic carbon isotopes (δ13Corg), radiocarbon (14C) activity of organic matter in bulk suspended sediments collected seasonally from the upper and middle Yellow River, to quantify the compositions and fluxes of the POC and to assess its sources (biospheric and petrogenic POC, i.e. POCbio and POCpetro, respectively). The results showed that the POC loading of sediments was controlled by mineralogy, grain size and specific surface area of loess particles. The Fmod of POC (0.71 to 0.31) can be explained by mixing of POCpetro with modern and aged POCbio. A binary mixing model based on the hyperbolic relationship of the Fmod and OCtotal revealed a wide range of ages of POCbio from 1300 to 11100 14C years. Relative to the upstream station, the annual POCbio and POCpetro fluxes in the Yellow River are more than doubled after it flows crossing the CLP within 35% drainage area gain, resulting in POCbio and POCpetro yields of the CLP at 3.50 ± 0.59 and 0.48 ± 0.49 tC/km2/yr, respectively. POC flux seasonal variation revealed that monsoon rainfall exerts a first-order control on the export of both POCbio and POCpetro from the CLP to the Yellow River, resulting in more than 90% of the annual POC exported during the monsoon season. Around one third of annual POC erosional flux was transported during a storm event period, highlighting the important role of extreme events in POC export in this large river. © 2020 John Wiley & Sons, Ltd. |
| Keywords: | Chinese Loess Plateau the Yellow River particulate organic carbon annual fluxes radiocarbon |