Detection And Characterization Of Dissolved Organic Matter(DOM) In Jinpen Reservoir

Jinpen Reservoir is located in Xi'an Heihe river basin,which is a deep and layered reservoir.It?s thermal stratification was monomitic.In the fall,the pollutants are released from sediment,which resulted in the secondary pollution of water and affect the quality of water.This study is about the characteristic and variety of dissolved organic matter(DOM)in Jinpen Reservoir during 2015-2017.Three-dimensional fluorescence spectroscopy-parallel factor analysis method,combined with UV-Visible absorption spectroscopy were applied to analyze the characteristics of DOM temporally and spatially,determine the composition,chemical characteristics,pollution source and circulation of DOM.We discussed the effect of algae,microbial degradation and photo degradation to water DOM circulation.The interstitial water DOM characteristics were studied to explore the variety of reservoir interstitial water DOM;and the DOM Input and consumption balance of source water reservoir was preliminarily analyzed and studied.The results of this study include the following 4 aspects:(1)Source water DOM characteristics have significant seasonal variation.The reservoir from the winter of 2015 to the autumn of 2016,the total fluorescence intensity of water DOM is highest in winter,lowest in spring;in summer,the fluorescence intensity is higher than in spring,but remained low level,then the fluorescence intensity increased to a high level in autumn.Source water DOM fluorescence characteristics : a.in autumn and winter,DOM humification degree is strong,the new endogenous DOM is less;b.in spring and summer,water productivity is strong,the contribution of endogenous input is remarkable,and the contribution of exogenous input to DOM is relatively small,the degree of humification of DOM is very weak;c.in summer,the fluorescence characteristics of DOM in the upper and lower waters are significant;d.the reservoir water DOM have both endogenous and exogenous inputs.Source water DOM ultraviolet absorption spectrum characteristics: a.the absorption index 350 a was lowest in spring,and higher in winter and summer,and there is a significant difference in vertical water in summer,which is complementary to the fluorescence intensity;b.the spectral slope ratio SR also has significant seasonal variation,indicating that light had a significant influence on the physical and chemical characteristics of DOM.The seasonal variation of DOM is mainly affected by the growth and death of algae and the degradation of organic matter under strong light condition.In spring and summer,some of the DOM is degraded,which leads to the lower total fluorescence intensity of DOM.In autumn,phytoplankton and aquatic organisms began to death,the residue degradation products increased the content of organic matter in water and the exogenous input leads to higher fluorescence intensity of DOM in winter.The photo degradation is the major cause of the difference in DOM characteristics between upper and lower layers in summer.(2)The study found no significant correlation between DOC(total organic carbon)and DOM fluorescence intensity.The results showed that the natural organic substance without fluorescence group in DOC is relatively larger.However,there was a negative correlation between 350 a and chlorophyll a,fluorescence intensity of humic substances and chlorophyll a,which indicated that the photo degradation had a crucial effect on the characteristics of DOM.There was no significant correlation between the fluorescence intensity of DOM and TN,TP and other nutrient concentrations,which showed that the migration and transformation behavior of N and P elements are not closely related to DOM in Jinpen reservoir.(3)Based on the study of DOM characteristics of sediment interstitial water DOM,it?s found that the proteins in interstitial water have stronger fluorescence.The DOM characteristics of different sampling points and different water states were significantly different.The fluorescence intensity of DOM in interstitial water was higher in the layered phase,and the fulvic acid was the main fluorescence component.The fluorescence intensity decreased during the mixed phase and tryptophan was the main fluorescent component.(4)In winter,DOM is dominated by input,and organic matter concentration was higher;in spring,water DOM input less,mainly in consumption,and organic matter concentration is lowest;in summer,water DOM input is more,and the consumption is more,the concentration of organic matter in the middle level;in autumn,water DOM consumption decreased,input increased,and organic matter concentration rose to a higher level.The dissolved organic matter in Jinpen reservoir is in dynamic equilibrium throughout the year.