Effects of Sediment Delivery Changes on Carbon Burial Within the Modern and Abandoned Delta Lobes of the Yellow River, China

摘要

Globally, deltaic wetlands sequester large volumes of terrestrial and marine-derived organic carbon. Diminishing sediment supply via river diversions, dams, and/or sea level rise threatens this stored carbon by enhancing erosion, thereby potentially releasing CO2 back to the atmosphere during remineralization of organic matter. The Yellow River delta, located in the Bohai Sea, China, has undergone intense anthropogenic manipulation since the 1950s including rerouting of the river mouth to expand the delta for oil exploitation. The goal of this study is to identify the impacts of river course diversions on sources and rates of carbon burial in the modern and abandoned delta lobes of the Yellow River delta. In 2016, we collected four cores total in abandoned and modern deltaic lobes and measured vertical accretion, total carbon, total nitrogen, delta C-13, and n-alkanes. The highest average mass accretion rate of 12,470.1gm(-2)year(-1) is observed in the abandoned delta, although it no longer receives direct river sediment input. The modern and abandoned deltas are currently outpacing sea level rise, but vertical accretion rates are influenced by sediment trapping practices in the modern delta and redistribution of eroded sediments in the abandoned. Average carbon burial rates across both delta sites vary between 7.2 and 14.9gOCm(-2)year(-1). Sediment-associated carbon at both sites is dominantly sourced from the Loess Plateau. To conserve wetlands across the Yellow River delta, sediment management practices that periodically reintroduce sediment-laden river water to former river courses, such as in the Mississippi delta, are suggested.