Apparent ages of suspended sediment and soil erosion of the Pearl River (Zhujiang) drainage basin

The carbon isotopic composition (Δ¹⁴C, δ¹³C) and apparent ages of suspended sediment were determined in the Pearl River in the years 1998, 2000 and 2005. These results indicate that suspended POC consists mostly of young carbon and some “old carbon”. Apparent ages of suspended POC range from 540 to 2050 a BP. The apparent ages are older in the Xijiang and Beijiang Rivers, while these values are variable in the Dongjiang River, including old and young samples. The suspended POC δ¹³C values increase with increasing Δ¹⁴C in the Pearl River, indicating that its source is soil and bedrock from depths under 15–30 cm. Since the organic carbon of the surface soil is quickly decomposed when it enters the rivers, its carbon isotopic characteristics are insignificant in suspended sediment. In the Pearl River drainage basin, there are areas with more severe soil erosion than others. For example, erosion is much more severe in the Xijiang River drainage basin when compared to the light soil erosion in the Dongjiang River drainage basin.