Enhanced biogenic carbon emissions in inland waterways: Insights from the Beijing-Hangzhou Grand Canal, China

Abstract

Rivers, being the first recipients of terrestrial organic matter, actively decompose this material and serve as hotspots for biogenic carbon emissions, including carbon dioxide (CO₂) and methane (CH₄), a process that is often regulated by river hydrodynamics. Water transportation, a widely used economic mode, alters river hydrodynamics and potentially impacts biogenic carbon emissions. To explore this impact, this study investigated CO₂ and CH₄ emissions in the Beijing-Hangzhou Grand Canal (BHGC), the world’s longest canal, and compared them with those in its undisturbed tributaries. The results indicated that ship disturbances reduced CH₄ production but greatly enhanced CO₂ release, ultimately leading to an increase in the CO₂-equivalents (CO₂-eq). Compared to its tributaries, the BHGC exhibited a fourfold increase in CO₂-eq. Ship disturbances resuspended riverbed sediments, resulting in a 40% decrease in organic carbon burial per unit area of sediment. The suspended organic carbon promoted its decomposition in the water, leading to increased CO₂ production, while the oxygen-rich environment in the water reduced CH₄ production. These findings add our understanding of the impacts of shipping activities on river biogeochemical cycling.