The isotopic composition and fluxes of particulate organic carbon exported from the eastern margin of the Tibetan Plateau

Jin, Wang; Hilton, Robert; Jin, Zhangdong; Zhang, Fei; Densmore, Alexander L.; Gröcke, Darren R.; Xu, Xiaomei; Li, Gen; West, A. Joshua

doi:10.1016/j.gca.2019.02.031

Cited by 19 publications

(47 citation statements)

References 61 publications

(132 reference statements)

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“…This pattern is consistent with the results of other rivers (e.g. Wang et al, 2019). The relationships of the POC in the upper and middle Yellow River could be explained by a mixture of relatively high OC total , commonly 13 C depleted and 14 C enriched POC from terrestrial biosphere, with relatively lower OC total , generally 13 C enriched and 14 C depleted POC from rocks and/or aged OC from loess and paleosol (Figures 5, 7a, b) (Hilton et al, 2015; Clark et al, 2017a).…”

Section: Discussionsupporting

confidence: 93%

“…Suspended sediment POC from the TDG and LM stations show that δ 13 C org composition is more similar to C 3 plants, as observed downstream (KL) (Figure 5a) (Tao et al, 2015a, 2015b; Xue et al, 2017), indicating a negligible contribution by C 4 plants to POC in the Yellow River. Meanwhile, we note that the F mod of the bulk POC in the suspended sediments ranging from 0.31 to 0.71 at the TDG and LM stations require contribution of old POC bio and/or POC petro , both which could also influence δ 13 C org values (Wang et al, 2012, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…This approach links the F mod measurement to the relevant proportions of POC bio and POC petro by the equation:

F_{\mod} \times {OC}_{total} = ((), F_{\mod ‐ bio} \times {OC}_{bio}) + ((), F_{\mod ‐ petro} \times {OC}_{petro})

where F mod is the measured 14 C composition of the sample and OC total is the POC content, OC bio (%) and OC petro (%) are the contents of POC bio and POC petro in the sample, while F mod‐bio and F mod‐petro are the 14 C composition of the POC bio and POC petro , respectively. Since OC bio = OC total – OC petro and F mod‐petro = 0 (Blair et al, 2003; Galy et al, 2008a; Torres et al, 2017; Wang et al, 2019), the formula produces a hyperbolic equation:

F_{\mod} = F_{\mod ‐ bio} - ((), F_{\mod ‐ bio} \times {OC}_{petro}) / ((), {OC}_{total})

The equation describes a hyperbola that asymptote equals to F mod‐bio and intercept with the x ‐axis equals to value of OC petro (Figure 2) (Hemingway et al, 2018; Wang et al, 2019). This regression can describe the F mod and OC total well when the OC petro and F mod‐bio are identical across all samples.…”

Section: Sampling and Methodsmentioning

confidence: 99%

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The sources and seasonal fluxes of particulate organic carbon in the Yellow River

Jin

Wang

et al. 2020

Earth Surf Processes Landf

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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.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

“…This approach links the F mod measurement to the relevant proportions of POC bio and POC petro by the equation:

F_{\mod} \times {OC}_{total} = ((), F_{\mod ‐ bio} \times {OC}_{bio}) + ((), F_{\mod ‐ petro} \times {OC}_{petro})

F_{\mod} = F_{\mod ‐ bio} - ((), F_{\mod ‐ bio} \times {OC}_{petro}) / ((), {OC}_{total})

Section: Sampling and Methodsmentioning

confidence: 99%

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The sources and seasonal fluxes of particulate organic carbon in the Yellow River

Jin

Wang

et al. 2020

Earth Surf Processes Landf

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“…4 b and 4c ). We suggest that degradation of ancient carbon released from melting glaciers and permafrost can constitute an important carbon source for the atmosphere 46 , 47 .…”

Section: Resultsmentioning

confidence: 96%

Substantial decrease in CO2 emissions from Chinese inland waters due to global change

et al. 2021

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Carbon dioxide (CO2) evasion from inland waters is an important component of the global carbon cycle. However, it remains unknown how global change affects CO2 emissions over longer time scales. Here, we present seasonal and annual fluxes of CO2 emissions from streams, rivers, lakes, and reservoirs throughout China and quantify their changes over the past three decades. We found that the CO2 emissions declined from 138 ± 31 Tg C yr−1 in the 1980s to 98 ± 19 Tg C yr−1 in the 2010s. Our results suggest that this unexpected decrease was driven by a combination of environmental alterations, including massive conversion of free-flowing rivers to reservoirs and widespread implementation of reforestation programs. Meanwhile, we found increasing CO2 emissions from the Tibetan Plateau inland waters, likely attributable to increased terrestrial deliveries of organic carbon and expanded surface area due to climate change. We suggest that the CO2 emissions from Chinese inland waters have greatly offset the terrestrial carbon sink and are therefore a key component of China’s carbon budget.

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“…In our model, the mean annual runoff and runoff variability help determine the sediment transport rate (Equation 6 that depends on Equation 7) and therefore in the river export of OC. These factors have been highlighted as important for the transport of particulate OC in mountain rivers (Hilton, 2017;Wang et al, 2019). The fate of landslide-mobilized OC is sensitive to the export time, which is a ratio between the volume of fine sediment available for transport and the sediment transport rate.…”

Section: The Role Of Climate In Landslide Oc Evacuationmentioning

confidence: 99%

Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model

Croissant¹,

Hilton²,

Li³

et al. 2020

Preprint

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Abstract. In mountain ranges, earthquakes can trigger widespread landsliding and mobilise large amounts of organic carbon by eroding soil and vegetation from hillslopes. Following a major earthquake, the landslide-mobilised organic carbon can be exported from river catchments by physical sediment transport processes, or stored within the landscape where it may be degraded by heterotrophic respiration. The competition between these physical and biogeochemical processes governs a net transfer of carbon between the atmosphere and sedimentary organic matter, yet their relative importance following a large landslide-triggering earthquake remains poorly constrained. Here, we propose a model framework to quantify the post-seismic redistribution of soil-derived organic carbon. The approach combines predictions based on empirical observations of co-seismic sediment mobilisation, with a description of the physical and biogeochemical processes involved after the earthquake. Earthquake-triggered landslide populations are generated by randomly sampling a landslide area distribution, a proportion of which is initially connected to the fluvial network. Initially disconnected landslide deposits are transported downslope and connected to rivers at a constant velocity in the post-seismic period. Disconnected landslide deposits lose organic carbon by heterotrophic oxidation, while connected deposits lose organic carbon synchronously by both oxidation and river export. The modelling approach is numerically efficient and allows us to explore a large range of parameter values that exert a control on the fate of organic carbon in the upland erosional system. We explore the role of the climatic context (in terms of mean annual runoff and runoff variability) and rates of organic matter degradation using single and multi-pool models. Our results highlight that the redistribution of organic carbon is strongly controlled by the annual runoff and the extent of landslide connection, but less so by the choice of organic matter degradation model. In the context of mountain ranges typical of the southwest Pacific region, we find that model configurations allow for more than 90 % of the landslide-mobilized carbon to be exported from mountain catchments. A simulation of earthquake cycles suggests efficient transfer of organic carbon out of a mountain range during the first decade of the post-seismic period. Pulsed erosion of organic matter by earthquake-triggered landslides therefore offers an effective process to promote carbon sequestration in sedimentary deposits over thousands of years.

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The isotopic composition and fluxes of particulate organic carbon exported from the eastern margin of the Tibetan Plateau

Cited by 19 publications

References 61 publications

The sources and seasonal fluxes of particulate organic carbon in the Yellow River

The sources and seasonal fluxes of particulate organic carbon in the Yellow River

Substantial decrease in CO2 emissions from Chinese inland waters due to global change

Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model

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