Keywords: 
• Pearl River, suspended matter,  /
• &delta /
• 13C，soil erosion /
•  /

Abstract: This article describes the changes of environment and vegetation of the Pearl River (Zhujiang) drainage basin by 13C/12C ratios (δ13C value) of particulate organic carbon (POC) and the content of POC, which can be used as effective indicators of the changes of vegetation, and also provides a new way for studying the environmental changes in shorttime scale. 
  The organic carbon isotopes composition of suspended matter from the Pearl River identifies the vegetation cover and soil erosion of their watershed. Suspended matter from Beijiang River, the tributary of Pearl River, emphasizes the sole influence of organic matter derived from C3rich plants. Suspended matter from the Xijiang River and Dongjiang River emphasizes the influence of organic matter derived from C3 and C4 plants. In normal seasons, it shows that the influence of organic matter derived from C3 plants in Xijiang and Dongjiang River. The δ13C value of POC gradually went up in Dongjiang River suspended matter from 1990 to 1999, and it varied from 17.8‰ to 26.1‰. Some suspended matter from the Dongjiang River has extremely high δ13C values in flood season (up to 17.6 ). These high values may be the result of severe erosion in the densely populated and intensively farmed region of the middle and lower reaches of Dongjiang River drainage basin. The erosion degree of the Dongjiang River drainage basin was greater than that of the Xijiang River.