Carbon And Nitrogen Isotopes Of Source Organic Matter In Northern

Source organic matter in water for the assessment of watershed soil erosion and Nutritional-quality has a very important role. The suspended particles,surface sediment,dominant plant and soil were collected in the Upper Reaches of the Chaobai River and Yeyahu wetland in northern Beijing.Elemental Contents (OC/TN) and stable carbon isotopic composition were analyzed and then employed to trace the sources of organic matter. At last, a three-end-Member mixing model was utilized to assess quantitatively contribution of different sources of organic matter in suspended particles and surface sediment.The result indicate that the carbon and nitrogen isotopes in the the suspended particles,surface sediment are different in the Upper Reaches of the Chaobai River and Yeyahu wetland. It was found that the ratio of carbon and nitrogen isotopic were-27.75%o～-21.58%o and 1.32‰～6.74‰in the surface sediments, while they are-29.34‰～-25.91‰and-0.34‰～6.36‰in the suspended particles respectively in the Upper Reaches of the Chaobai River. Furthermore, it was found that the ratio of carbon and nitrogen isotopic were-27.07‰～-23.05%o and 0.24‰～7.86‰in the surface sediments, while they are-29.76‰～-26.70‰and-1.10‰～7.59‰in the suspended particles respectively in the Yeyahu wetland.The analysis of Source organic matter indicated that soil organic matter is a significant contributor to sediment OM, while the vascular aquatic plants to suspended POM in the Chao River and the Bai River. This reveals that sediment is from particles of soil erosion, and suspended particles was washed away by river. Soil organic matter is a significant contributor to sediment OM and suspended POM in the Miyun reservoir, and a source of sedimentary organic matters in the Miyun reservoir is mainly carried by the Chao River and the Bai River, other source is from C4 vegetation growing around Miyun reservoir for individual point station. Aquatic algae is a significant contributor to sediment OM and suspended POM in the yeyahu wetland.Compared with the situation of Hebei province, the contribute of soil organic matters decreased obviously and river plankton vascular aquatic plants increased evidently in Beijing areas, especially in Bai River.This study reveals that the source of organic matter has a close relationship with the situation of soil erosion in the areas. Organic matter in river is mainly from outside source, and organic matter in lake is mainly from inside source.The reason of this difference is that there is vast outside source input and relative short hydraulic power remain time in river, but the environment is Closed and stable in lake.