CO 2 outgassing from the Yellow River network and its implications for riverine carbon cycle

作者：Lishan Ran, Xixi Lu, Huan Yang, Lingyu Li, Ruihong Yu, Huiguo Sun, Jingtai Han · 发表于：Journal of Geophysical Research Biogeosciences · 年份：2015 · DOI：10.1002/2015jg002982 · 被引用次数：112 · 研究领域：Marine and coastal ecosystems、Atmospheric and Environmental Gas Dynamics、Oceanographic and Atmospheric Processes

Abstract CO 2 outgassing across water‐air interface is an important, but poorly quantified, component of riverine carbon cycle, largely because the data needed for flux calculations are spatially and temporally sparse. Based on compiled data sets measured throughout the Yellow River watershed and chamber measurements on the main stem, this study investigates CO 2 evasion and assesses its implications for riverine carbon cycle. Fluxes of CO 2 evasion present significant spatial and seasonal variations. High effluxes are estimated in regions with intense rock weathering or severe soil erosion that mobilizes organic carbon into the river network. By integrating seasonal changes of water surface area and gas transfer velocity ( k ), the CO 2 efflux is estimated at 7.9 ± 1.2 Tg C yr −1 with a mean k of 42.1 ± 16.9 cm h −1 . Unlike in lake and estuarine environments where wind is the main generator of turbulence, k is more correlated with flow velocity changes. CO 2 evasion in the Yellow River network constitutes an important pathway in its riverine carbon cycling. Analyzing the watershed‐scale carbon budget indicates that 35% of the carbon exported into the Yellow River network from land is degassed during fluvial transport. The CO 2 efflux is comparable to the carbon burial rate, while both larger than the fluvial export to the ocean. Comparing CO 2 evasion with ecosystem productivity in the Yellow River watershed shows that its ecosystem carbon sink has previously been overestim...