Effect of human‐controlled hydrological regime on the source, transport, and flux of particulate organic carbon from the lower Huanghe (Yellow River)

Abstract

Evaluating the role of fluvial transfer of terrestrial organic carbon (OC) and subsequent burial in the global carbon cycle requires the sources and fluxes of fluvial OC to be assessed, which remains poorly constrained in the Huanghe (Yellow River). Here, we report the elemental, stable isotopic, and radiocarbon activity of particulate organic carbon (POC) sampled at the outlet of Huanghe in 2012–2013. We show that the Huanghe riverine POC can be explained by binary mixing of fossil (POCfossil) and non‐fossil (POCnon‐fossil) components, the former may reach ~40% of the total POC. The Huanghe POCnon‐fossil is mostly sourced from C3 plants, with a mean residence time of c. 2200 years. The current human‐controlled hydrological regime strongly influenced the POC sources, transport modes, and fluxes. In 2012–2013, the Huanghe delivered 0.73 Tg (1 Tg = 1012 g) of POC to the sea, and about 28% of the annual POC flux occurred within a short human induced flood event. Globally, the Huanghe should be one of the largest rivers in the transfer and re‐burial of fossil OC. However, the fate of Huanghe fossil OC is still unconstrained and needs to be further investigated. Copyright © 2015 John Wiley & Sons, Ltd.

Humans and the Earth's surface

“…In the last 50 years the water level, due to water diversions, has dropped from 395 m to about 430 m below sea level. Hu et al (2015) analyzed the effect of hydrological regime managed by humans, on the source, transport, and flux of particulate organic carbon (POC) from the lower Huanghe (Yellow River, China). the reactivation of palaeochannels with subsidence, sinkholes, and landslides).…”

Distribution and sources of organic matter in surface sediments of Bohai Sea near the Yellow River Estuary, China

“…The estimated sediment discharge of the YR before 1970 was~1.08 Gt a À1 ; the discharge rapidly dropped to~0.15 Gt a À1 since 2000 due to reduced rainfall and artificial regulation of water and sediment discharge (Wang et al, 2006). Reduced freshwater and sediment discharge profoundly impacted the physical, biogeochemical and biological environment in the sea surrounding the delta of the YR. For example, Hu et al (2015) estimated that the particulate organic carbon discharge of the YR has decreased from 4. Su et al (2015) reported that the DIN concentrations near the YR mouth can reach up to 70 mM in the summer due to increased river input.…”

Total organic carbon fluxes of the Red River system (Vietnam)

“…The percentages of POC in TSS at the four gauging stations varied from 0.6 to 6.1% with a mean value of 1.5 ± 0.6% for the whole Red River system and are similar to those of other rivers in Asia such as the Changjiang (1.16%) (Wu et al ), the Xijiang (1.2%) (Sun et al , ) , the Brahmaputra (0.50%), and the lower Yellow (0.75%) (Hu et al ), the Pearl River Delta (1.5–2.5%) (Ni et al , ) but are lower than in the Congo River (3.9–11.5%) (Coynel et al ).…”

“…() found a value of 1.0 in the Chanjiang River. Values from the Ganges River are even lower (0.3; Zhang et al ) , as in the Yellow River (0.08–0.16; Ran et al , ; Hu et al ) and Lanyang His Rivers (0.16; Kao and Liu ). The low values are due to the high riverine POC fluxes (70%) in this region.…”

“…They were, however, lower than the global mean value of 5 mgC L −1 provided by Meybeck (). The Red River values were also much lower than in the Yellow River (116 mgC L −1 ) (Hu et al ), where 90% of the TOC loading is transported as POC despite the existence of numerous reservoir impoundments (Ran et al , ) (Table ).…”