Tianjin Surface Water, Surface Sediments And Plant Organic Nitrogen Isotope Characteristics And Their Environmental Significance

It is one of the important wetland nutrient cycle.The river is a wetland ecosystem which is an important part of the earth’s channels of terrestrial ecosystems in the global cycle. Nitrogen is limiting nutrient of primary productivity in river.With the developing of industrial civilization, Human activities caused the exogenous nitrogen input significantly increased and exacerbated the eutrophication of aquatic ecosystems process. Nutrient cycling is an important process with migration and transformation of nitrogen in the river ecosystem and river wetland have become the organic nitrogen nitrogen source or sink of the river ecosystems.In this paper, on the basis of previous research, I try to utilize the nitrogen stable isotope methods to obtaining informations about Tianjin HaiHe River environmental change and the relationship between the Tianjin Haihe River Basin environment changes and watershed characteristics of organic nitrogen isotope values which provide scientific ideas for river protection and management for the wetland region.Suspended matter in surface sediments can reflect the watershed of environmental information and reveal the process of nitrogen biogeochemical cycles on a regional scale as the distribution characteristics and environmental significance through a typical plant nitrogen isotope composition.The nitrogen isotope reflects the contribution of different provenance and the fractionation of inorganic nitrogen in the absorption process.Of course, it will be fed back to the isotopic composition of organic matter about biogeochemical processes.The river particulate organic nitrogen study not only provides important information on the nitrogen cycle, and also provides the record of natural and human activities in the watershed. The particulate organic nitrogen contents in surface sediments, plants and water and nitrogen stable isotope distribution characteristics can reveal the trend of the environment. This paper based on organic nitrogen isotope (δ15N) technology in order to stabilize organic nitrogen isotopic characteristics of the Tianjin Haihe River and its environmental significance. As to analysis methods of organic nitrogen stable isotope the δ15N characteristics of suspended particulate matter, surface sediment and plant indicate nitrogen migration, transformation and other biogeochemical processes about different samplings of2011from river ecosystem.This study analyzed organic nitrogen stable isotopic composition and C/N ratio of the characteristics of Tianjin surface water59suspended particulate matter samples,44plant samples and41surface sediment samples. The study found that samples of organic matter and stable nitrogen isotope composition and biogeochemical processes does not directly indicate the source of organic nitrogen and composition. Organic nitrogen isotope of surface water that is not high degree of dispersion within the basin δ15NPON and C/N (R2=0.016). Obviously, organic nitrogen of the river wetland may be strong role of human disturbance. Wetland surface sediments contain large quantities of organic matter and rich nitrogen. Organic nitrogen in surface sediments is based on exogenous inputs. Organic nitrogen isotopes of particulate organic nitrogen and floating plants in the surface sediments will be more effective in water organic matter sources, migration, and output. The following is the main conclusions of this paper:(1) Nitrogen isotopic of particulate organic matter mean higher sewage impact of exogenous human activities.δ15NPON value and C/N ratio in surface water has a low correlation (R2=0.016).δ15NPON means intense microbial activity change.Organic C/N ratios range from C/N:3.7～10.2between the microbes and phytoplankton characteristics which are suspended particulate organic nitrogen composition.(2) δ15NPON of majority urban samples are more than2O‰; most of δ15NPON in the agricultural area are less than10%o, such the low δ15NPON samples may be affected by the impact of agricultural activities, mainly by exogenousinput nitrification; the reservoir δ15NOPN value to less than15%o, reflects the endogenous characteristics, that is obviously the contribution of algae, plankton and micro-organisms.(3) Organic particulate matter caused δ15N reduction more obvious than the mineralization increased, therefore to performance lower for δ15NPON, but does not affect the C/N value. This study, the main reason of the organic particulate nitrogen samples low δ15NPON value in agricultural areas water may be an important reason for denitrification and the exogenous input cause δ15NPON down. (4) Organic nitrogen from the water, phytoplankton and organic particulate matter of urban sewage discharge, the smaller the proportion of organic nitrogen contribution to soil emission. Tianjin surface water is broadly divided into two categories of the sewage side and eutrophic static water.(5)δ15NPON value and TN content is extremely low (R2=0.0073); δ15NPON and NO3-content is weak positive correlation (R2=0.077), indicating that δ15N values tend to inorganic nitrogen isotopic values. δ15NPON δ13CPOC content with a low positive correlation because of microbial activity.(6) Tianjin wetland emergent plants (mainly reed) organic nitrogen δ15N values ranged from3.32‰to19.89‰, average of11.03‰; emergent plants C/N ratio range:5.55to23.06, average of14.93.δ15N value is related to emergent plants DIN assimilation, absorption, and background concentrations.(7) Floating wetland plants (for plants) organic nitrogen δ15N values ranged from4.77‰to22.55‰, average of14.2‰; floating plant C/N ratio range:5.60to14.54, average of9.45.δ15N values and δ15NPON value highly positively correlated, R2=0.54. Higher δ15N values from water absorption and plant assimilation.(8)δ15N of organic nitrogen values rang from2.25‰to12.92‰from surface sediment, averaging7.42‰, Organic C/N ratio:6.43to22.04. Surface sediments is basically soil organic matter and terrigenous organic matter in mixing process.