Spectral Analysis And Source Analysis Of Dissolved Organic Matter(DOM) In Pai River And Nanfei River

Pai River and Nanfei River are important rivers to flow into Chaohu Lake.In order to strengthen the environmental management and improve the quality of water environment in Chaohu Lake,we collected water of Pai River in December 2017,water and surface sediments of Nanfei River in spring?March 2018?and in summer?July 2018?.And combined with parallel factor analysis?PARAFAC?model and correlation analysis,three-dimensional fluorescence excitation-emission matrix?3D-EEM?and ultraviolet-visible absorption spectrum?UVAS?were used to study the distribution characteristics,sources,temporal and spatial changes and influencing factors of DOM in Pai River and Nanfei River,one of the important.Those could provide some basic data for improving the pollution carrying capacity of rivers and comprehensive environmental management of Chaohu Lake.In addition,according to the sources of DOM,the scheme of external pollution control and internal pollution reduction was formulated.The results showed that:?1?Using PARAFAC model to analyze 3D-EEM,two kinds of humus-like components?including ultraviolet fulvic acid-like C1 and visible fulvic acid-like C3?and two kinds of protein-like components?including tryptophan C2 and tyrosine C4?were identified form Pai River;two humic-like components?including ultraviolet fulvic acid-like C1 and humic acid-like C3?and one protein-like component?tryptophan-like C2?were identified from Nanfei River.Humus-like substances were humic acid and fulvic acid which came from exogenous input,while protein-like substances were affected by the production of phytoplankton and microorganisms in the terrestrial and overlying water.In addition,the DOM of Pai River was mainly dominated by protein-like substances,and the DOM of Nanfei River was jointly affected by humic-like substances and protein-like substances.?2?The fluorescence intensity of each component was used to represent the relative concentration of different components in DOM.The spatial variation of the total fluorescence intensity of the DOM in Pai River was slightly lower in the downstream than in the upstream,and the variation of humic-like substances?C1 and C3?was smaller than that of protein-like substances?C2 and C4?.And in Nanfei River,the total fluorescence intensity of DOM in spring was higher,and the vertical differences of the three fluorescence components in surface sediments were higher.?3?Through analysing the fluorescence index?FI??the biological index?BIX??the humification index?HIX??the ratio of A to C?r?and the freshness index??:??,DOM had weak degree of humification and obvious autogenetic characteristics in Pai River,which had both endogenous input and exogenous input.And in Nanfei River,the DOM of water and surface sediments in spring had both the characteristics of humification and autobiogenesis,but the autobiogenic characteristics were stronger,and the humification characteristics in summer were slightly more obvious.?4?The values of a?280?and a?355?of DOM in Pai River were significantly correlated with the fluorescence intensity of C1 and C4,respectively.The results indicated that the protein-like substances contents of DOM were relatively higher,while the humic-like substances contents were lower.And,the values a?280?and a?355?had obvious vertical spatial variations in Nanfei River.Humic-like substances and protein-like substances in surface sediments decreased slightly in summer compared with that in spring,but increased in summer.Besides,the spectral slope(S_275²95)and the molecular weight characteristic parameter value?M?were both negatively correlated with the total fluorescence intensity of DOM in Nanfei River.?5?The fluorescence intensities of DOM components in Pai River and Nanfei River were correlated with NH₃-N,TP and COD,respectively.The compositions of DOM were dominated by organic matter pollution in Pai River.And in Nanfei River,the sources of components were complex,humic-like substances and protein-like substances might have homology.Moreover,the migration and transformation of organic matter pollution,nitrogen and phosphorus had an impact on the composition of DOM.?6?The DOM of Pai River could be reduced mainly by controlling exogenous pollution input.However,DOM reductions in Nanfei River need to be achieved from external pollution control and internal pollution reduction.