珠江水体悬浮物碳稳定同位素组成与流域土壤侵蚀研究

The Study of Stable Carbon Isotope Composition of Riverine Suspended Matter and Soil Erosion of the Pearl River Drainage Basin

以珠江流域水体悬浮物为研究对象,对其碳稳定同位素组成(δ13C)及颗粒有机碳(POC)的含量进行了测定和研究。结果表明:河流悬浮物同位素组成与珠江流域植被分布格局、土壤有机质密切相关;珠江悬浮物碳同位素组成主要受C3植被影响,其中,西江悬浮物碳同位素组成表现出较强的C4植被特征。东江水体悬浮物碳同位素组成在洪水季节表现出较强的C4植被特征,其它季节则表现出C3植被特征;北江水体悬浮物碳同位素组成无明显的C4植被特征。东江悬浮物样品POCδ13C值呈逐年上升趋势,与近年来流域内植被破坏和土壤侵蚀加剧相对应,并显示其侵蚀程度超过西江流域。

This article describes the changes of environment and vegetation of the Pearl River （Zhujiang） drainage basin by δ^C/δ^C ratios （δ^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 C3-rieh plants. Suspended matter from the Xijiang River and Dongjiang River emphasizes the influence of organic matter derived from C3 and C4 plants. In normal seasons, it shows that the influence of organic matter derived from C3 plants in Xijiang and Dongiiang River. The δ^C value of POC gradually went up in Dongjiang River suspended matter from 1990 to Some suspended matter from the Dongjiang River has extremely high These high values may be the result of severe erosion in the densely 1999, and it varied from -17.8‰ to -26.1‰. δ^13C values in flood season （up to -17.6 ）. 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.