Erosion-induced massive organic carbon burial and carbon emission in the Yellow River basin, China

Abstract

Abstract. Soil erosion and terrestrial deposition of soil organic carbon (SOC) can potentially play a significant role in global carbon cycling. Assessing the redistribution of SOC during erosion and subsequent transport and burial is of critical importance. Using hydrological records of soil erosion and sediment load, and compiled organic carbon (OC) data, estimates of the eroded soils and OC induced by water in the Yellow River basin during the period 1950-2010 were assembled. The Yellow River basin has experienced intense soil erosion due to combined impact of natural process and human activity. Over the period, 134.2 ± 24.7 Gt of soils and 1.07 ± 0.15 Gt of OC have been eroded from hillslopes based on a soil erosion rate of 1.7-2.5 Gt yr −1 . Approximately 63 % of the eroded soils were deposited in the river system, while only 37 % were discharged into the ocean. For the OC budget, approximately 0.53 ± 0.21 Gt (49.5 %) was buried in the river system, 0.25 ± 0.14 Gt (23.5 %) was delivered into the ocean, and the remaining 0.289 ± 0.294 Gt (27 %) was decomposed during the erosion and transport processes. This validates the commonly held assumption that 20-40 % of the eroded OC would be oxidized after erosion. Erosion-induced OC redistribution on the landscape likely represented a carbon source, although a large proportion of OC was buried. In addition, about half of the terrestrially redeposited OC (49.4 %) was buried behind dams, revealing the importance of dam trapping in sequestering the eroded OC. Although several uncertainties need to be better constrained, the obtained budgetary results provide a means of assessing the redistribution of the eroded OC within the Yellow River basin. Human activities have significantly altered its redistribution pattern over the past decades.

Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems: Concepts, emerging trends, and research challenges

“…Therefore, these data are limited in assessing how recent environmental changes taking place across Asian river systems have been altering riverine C fluxes. There have been few systematic assessments of effects of impoundments and water pollution on the C fluxes of Asian rivers (Sarma et al, 2011;Ran et al, 2014;Li and Bush, 2016). For example, a cascade of dams constructed along the upper Mekong River since the 1990s have been implicated to 130 cause a wide range of downstream impacts including decreases in water and sediment flow (Li and Bush, 2016).…”

“…More than 110,000 silt check dams have been constructed in the Loess Plateau since the 1950s, trapping approximately 21 billion tons of sediment in the reservoirs (Zhang et al, 2016). A conservative estimate indicates that the rate of annual POC trapping in more than 3,000 large dams (excluding 110,000 silt check dams) within the Yellow River basin can amount to 3.34.3 Tg C yr −1 (1 Tg 255 =10 12 g; Zhang et al, 2013;Ran et al, 2014), which is similar in magnitude to the total organic C export to the Bohai Sea (4.1 Tg C yr −1 ; Ran et al, 2014;Fig. 3).…”

“…As illustrated by the relatively high rate (27%) of CO2 emission from the POC eroded from the entire Yellow River basin (Ran et al, 2014;Fig. 3), the organic C in highly turbid waters of many Asian rivers can become an important source of CO2 during the fluvial transport and sediment storage.…”

“…4). The CO2 evasion from the fluvial 385 network of the whole basin was estimated at 4.7-7.9 Tg yr −1 , with >70% emitting from the tributaries draining the Loess Plateau (Ran et al, 2014(Ran et al, , 2015bFig. 3).…”

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

“…Galy and Eglinton, 2011;Martin et al, 2013) or direct ramped-pyrolysis radiocarbon analysis of SPM (e.g. According to Ran et al (2014), the Huanghe annually exported 4.11 Tg of POC (i.e. Nevertheless, the estimated bulk age of biogenic OC (c. 2200 years) in the Huanghe basin can be validated by a partial 'residence time' for the POC in soil (Time SOC ), which only takes into account the physical erosion processes (Lloret et al, 2013).…”