Historical Trends of Terrigenous Organic Carbon Transported by the Yangtze River (Changjiang) to East China Sea

Abstract:

In order to reconstruct the history of terrestrial discharge and human activities in recent 70 years, sediment core samples collected from the Yangtze River estuary were analyzed through lignin-phenols, pigments and stable isotopic (δ¹³C and δ¹⁵N) analysis. The variation of concentration and degradation of lignin phenols in sediments presents three stages, with higher concentration and lower degradation in the first 80 cm from the surface, lower concentration and higher degradation in the middle of the core (80cm ~ 170cm) and higher concentration and lower degradation from 170cm to 270cm, which are related to different periods affected by human activities respectively. Moreover, the flooding events of the Yangtze River in 1954 and 1998 also could be recognized through the sediment core samples. After the mid 1980s, sediment load of the Yangtze River has become an essential factor in affecting the discharge of terrigenous organic carbon, due to the building of dams. However, when comparing with other researches, owing to complicated sediment burial speeds and hydrodynamic conditions, as well as influences brought by vertical mixing in the Yangtze estuary, the effect of terrigenous organic carbon to the carbon cycle in this region should be further studied.