Distribution Characteristics and Sources of Sedimentary Organic Matter in the Pearl River Estuary and Adjacent Coastal Waters, Southern China

Geochemical descriptors (carbon, nitrogen contents, and their isotopes) of sedimentary organic matter (OM) were investigated in the Pearl River estuary (PRE) and adjacent coastal waters. The comprehensive geochemical data of surface and deep sediments were provided, and the sources of sedimentary OM were discussed in this area mainly impacted by human activities. Surface (1-10 cm) and deep (190-200 cm) sedimentary total organic carbon (TOC) were 1.2% and 0.6%, and total nitrogen (TN) contents were 0.09% and 0.05%, with delta C-13 of -24.3 parts per thousand and -24.5 parts per thousand, on the average, respectively. Higher TOC and TN contents combining with relatively negative delta C-13 values in surface sediments suggested the increasing OM inputs from rivers in recent years. Terrestrial organic carbon (OC) contents were 0.70% and 0.36%, and marine OC contents were 0.50% and 0.28% on the average, respectively, in surface and deep sediment. Surface terrestrial and marine OC were lower in river outfalls due to the high current energy, and deep terrestrial and marine OC showed the increasing trend away from the coast. Lower delta N-13 was mainly attributed to the influence of river sewage discharge in this study.