Riverine inputs of total organic carbon and suspended particulate matter from the Pearl River Delta to the coastal ocean off South China

A total of 1008 samples were collected from the eight major riverine runoff outlets in the Pearl River Delta (PRD) during 2005−2006 to estimate the fluxes of total organic carbon (TOC) to the coastal ocean off South China. The average dissolved organic carbon (DOC) concentration was 1.67 mg/L with a range of 1.38−2.13 mg/L. Concentrations of particulate organic carbon (POC) ranged from 2.66−4.12% of total suspended particulate matter (SPM). The fluxes of TOC and SPM from the PRD via the eight outlets were 9.2 × 105 and 2.5 × 107 tons/yr, respectively. Temporal variations in POC and DOC were observed at all outlets due to the large variability in runoff levels because of the seasonality of rainfall, and the riverine discharge amount was an important factor controlling TOC flux. The net contribution of organic carbon from the PRD to the coastal ocean represented approximately 0.1−0.2% of total organic carbon transported by rivers worldwide.