Beijing Water Sources In Water Suspended Particulate Organic Matter And Stable Carbon, Nitrogen Isotope Studies

Samples of suspended particulate matter were collected in water source in Chaobai watershed,Yeya Lake and Wenyu-Beiyun River, analyzed for carbon and nitrogen isotopic compositions. These isotopic compositions and C/N ratios were used to identifying the origins of particulate organic matter. The results show that:1.The carbon and nitrogen isotopic ratios in suspended particulate matter were-29.34‰～25.91‰and-O.96‰～+6.73‰in summer, while they were-30.75‰～-25.75‰and-0.83‰～+9.67‰in winter respectively. There were obvious seasonal variations in isotopic compositions observed in Chaobai watershed..2. The ratios of stable carbon isotope of surface sediments varied from-27.25‰to-21.58‰. The spatial change of surface sediments was dissimilar to SPM, indicated that, in the short term, the interaction between surface sediments and SPM is not significant.3. The carbon isotopic ratios in suspended particulate matter were-30.46‰～-26.70‰in Yeya Lake.They are much lighter than the ratios of Chaobai watershed. The nitrogen isotopic ratios in suspended particulate matter were+1.40‰～+7.59‰, these ratios are much heavier than the ratios of Chaobai watershed. The carbon isotopic ratios in suspended particulate matter were-30.36‰～-25.66‰in Wenyu-Beiyun River. They are much lighter than the ratios of Chao river. The nitrogen isotopic ratios in suspended particulate matter were-5.73‰～+2.30‰, these ratios are also much lighter than the ratios of Chaobai watershed.4.The relationships between SPM weight and POC%, PN% indicate that mineral matter coming from the erosion of terrigenous soils is the main component of SPM. But the stable carbon isotopes have no relativity to nitrogen isotopes both in Yeya Lake and Wenyu-Beiyun River study area.5.According to the analysis of POC by combiningδ13C,δ15N and C/N, the suspended particulate organic matter of Chaobai watershed was derived mainly from SOM-C3 and macrophyte in summer, while it was derived from SOM-C3 and plankton in winter. Surface sediments organic matter of Chaobai watershed was derived from SOM-C3. The suspended particulate organic matter of Yeya Lake was derived mainly from SOM-C3, while it of Wenyu-Beiyun River was derived mainly from plankton. 6.δ15N ratios reflect the combined results of information of sources and a series of biogeochemical processes. Althoughδ15N ratios could provide limited information of sources, it can be used to trace some special biogeochemistry processes.