Analysis Of The Organic Matter Sources In Beijing City River By Carbon And Nitrogen Isotopes Technology

The research of city river water organic matter sources by carbon and nitrogen isotope techniques can provides important basis of the river erosion and eutrophication assessment. This paper selects Beijing city river—Bei Yun river as the research object, Collection the surface water, sediment, suspended particulate matter, the surrounding soil and common plants samples conduct carbon, nitrogen isotope analysis. Discuss the carbon and nitrogen isotope composition and spatial distribution characteristics of various samples in Bei Yun River. Combination the carbon and nitrogen isotope composition and C/N ratio of various samples, Qualitative research the organic matter sources sediments and suspended particles, and using the multivariate mixture models for these sources contribution ratio conduct quantitative analysis.The results show that:the suspended particulate organic carbon (POC) in δ13C values in the range of-21.4to-31.2per thousand, average of-27.05per thousand (n=10), the δ13C values of tributary are above the Main stream; the δ13C values in Shun Yi District are the most "light", mean-30.25per thousand, Chao yang District δ13C values of the most" heavy", the average value of-23.05per thousand.δ13C relatively "light" samples from the woodland and forest vegetation area (Shun Yi District), rather than" heavy" samples derived from secondary grass vegetation and farm system, Chao yang District’s population density, per capita emissions, resulting the carbon isotope values in the Chao yang District " heavy" than other districts. The δ15N value of suspended paniculate matter-9.9～-4per thousand, average of-7.3per thousand, the mainstream and tributaries of the nitrogen isotope no difference (-7.53per thousand, and7.05per thousand). Chang ping District suspended particles δ15N values of the" heavy"(-5.6per thousand), Tong Zhou District suspended particles δ15N values of the" light"(-8.23per thousand). Suspended particulate nitrogen isotope values and surface water ln[NO3] no obvious linear relationship, description particulate organic matter origin is plural. The C/N ratio of suspended particulate average of8.6(n=10), C/N ratio greater than tributaries of C/N ratio in Bei Yun river. Suspended particulate organic carbon and nitrogen isotope is not significant linear relationship, the suspended particulate organic matter sources are not a single source, is multivariate mixed results. Suspended particulate organic matter sources are mainly two categories, one category from the surrounding soil erosion, another from the aquatic plankton, the algae contribution small effect.The δ13C values range from-8.6to-21.1per thousand in Surface sediment samples collected, average of-15.4per thousand (n=10); The δ13C (average of-13.97per thousand, n=6) of main stream are" heavier" than the tributaries (-17.33, n=4). Abundant water period (August) δ13C values are generally lower than the dry season (April) δ13C value. In abundant water period (August), rainfall big, large number of terrestrial organic matter in rainwater are carried into the river; and the dry season (April), surface sediment from land soil erosion are small effect, mainly from the river inside the aquatic phytoplankton and other physiological effects. The δ13C value variation of abundant water period and low water period in Bei Yun River, Showed that with the rain into the river basin organic matter contribution than in obvious contribution. The δ13C and chlorophyll have no linear relationship, that river algae contributing smaller. The δ15N values of surface sediment samples ranges from1.6per thousand to5.3per thousand, average of3.2per thousand (n=10). The δ15N of main stream values (3.23, n=6)" heavier" than tributaries (3, n=4); rainy season (August) δ15N values in the range of1.6per thousand to5.3per thousand, dry season (April) δ15N value range is0.3-4.7per thousand. The δ15N values in research area are consistent with the world estuary watershed. Abundant water period (August) δ15N value is generally higher than the dry season (April) δ15N values, in the Bei Yun river basin, with the rain water into the terrestrial organic matter contribution than river internal obvious contribution. Surface sediments and chlorophyll is no obvious linear relationship, algae is not the main factor of nitiogen pollution sources. Affected by many factors, the basin in surface sediments of stable nitrogen isotope space change is complicated, nitrogen isotope space and hydrological response to seasonal variation of nitrogen pollution is a series of biogeochemical processes and results, the source is not river inside of algae effect, more from terrestrial, and carbon isotope resulting inferences consistent.The carbon isotope value? in soil organic-iR.6～-7.3per thousand, average of-13.51per thousand (n=10), the main stream carbon isotope value of mean-12.93(n=6). The stable carbon isotope values of main stream are more volatile than tributaries, carbon isotope value of tributaries o mean less than the main stream. The815N of surface soil is-1.4per thousand to4.3per thousand, average of1.8per thousand (n=10), the main stream δ15N (1.55per thousand, n=6)" light" than tributaries (2.15, n=4). The C/N ratio in the range of11.8～39.7, average value is22.25(n=10), the mainstream and tributaries of the C/N ratio difference. The carbon isotope values range of plant samples:-29～-13perthousand, and the nature of C3plants and C4plants consisting entirely consistent. The obvious double peak characteristics showed that, Bei Yun river instructions for C3and C4plants mixed vegetation characteristics.The sediment organic matter has three main sources, soil organic matter, aquatic vascular plants and C4plants, algae and C3plants have small contribution. Abundant water period sediment source of organic matter in soil organic matter sources accounted for70%, while C4plants account for the sources of the20%, and some from the river inside of algae; dry season is the source of soil organic matter, C4plants and algae, aquatic vascular plant interaction. Main stream and tributaries of the source of organic matter in similar circumstances, both in the soil organic matter is the main source, aquatic vascular plants and C4plants into second major sources, algae contributing a small amount of sources.60～70%sampling points of organic matter is mainly derived from soil organic matter, that the sediment organic matter sources mainly for foreign.