Distribution of labile organic carbon using different extract method in the surface sediments of Pearl River Estuary

Labile organic carbon(LOC)is a chief component in marine sediment organic carbon.It is important to study different types of sediment LOC in estuaries for better understanding of its offshore migration and transformation process.The sediment LOC could provide a basis information for the research of global carbon cycle.In this study, we investigated the distribution patterns of the salt extractable carbon (SEC), water extractable carbon (WEC), chloroform fumigation extractable carbon (MBC) and acid hydrolysable carbon (AHC)in the surface sediment in Pearl River Estuary (PRE).The result showed the average content of SEC, WEC, MBC and AHC were 768.0×10^-6, 688.1×10^-6, 963.2×10^-6 and 3040.7×10^-6 in the PRE, respectively.The content of SEC and AHC decreased gradually from the northwest to the southeast, while the MBC content decreased gradually from the outside of PRE to the northwest region.The distribution of WEC was relatively homogenous.It suggested that the recalcitrant fraction of LOC from land input was mainly deposited in the western region, while MBC was mainly deposited in the southeastern outlets.In PRE, the high anthropogenic LOC content in the sediment would have the negative impact for the burial of organic carbon.