Analysis Of COD Characteristics And Accumulation In Dianchi Lake

Dianchi Lake is the largest freshwater lake in Yunnan Province,known as the plateau pearl.Watershed area of 2920 square kilometers,population of more than 3600 people。Dianchi Lake plays an important role in Kunming’s economic and social development and environmental development.With the attention of national governance,Dianchi Lake water quality continues to improve.Monitoring data found that from 2009 to 2014,Dianchi Lake total nitrogen total phosphorus decreased,but COD concentration has increased significantly.The COD of Dianchi Lake is mainly derived from exogenous inputs such as point source discharge,agricultural non-point source discharge,urban non-point source discharge and secondary metabolism of lake water biological metabolism and sediments.Based on the characteristics of different sources of COD in Dianchi Lake,the characteristics of COD and the degradation ability of different sources were investigated.The contribution of COD to lake was estimated based on the pollution load.Haihe River as a typical river into the city of rivers,the water from the spectral analysis found in the process of molecular weight reduction,fragmentation of a small part of the decomposition of small molecules(carbonyl,carboxyl)The characteristics of the fluorescence spectra are relatively stable.The characteristic absorption bands corresponding to the C=CH bonds in the particulate matter are the most active,and the strength is enhanced during the culture process,and the change of the first three days is obvious.And the intensity of the infrared absorption band corresponding to-CH3 in δ(-CH)aliphatic hydrocarbons gradually weakened,and the transition of-CH3 structure into δ(-CH)aliphatic hydrocarbons into three bonds.The process of degradation of the macromolecules such as carbonyl and carboxyl groups on the aromatic ring is studied by UV-Vis spectroscopy.Fluorescence spectra showed that the peak intensity of peak a(UV fulvic-like,Ex/Em = 230～270 nm/360-470nm)was higher than that of Haihe River in urban river,but the peak area decreased rapidly.This is related to the richness of agricultural protein from the surface of the river.Fourier transform infrared spectroscopy analysis found that the East River particulate matter in the process of strengthening the intensity of a greater degree of change.The structure of v(C-O),v(-COO-)and β(O-H)phenols in the organic matter of organic matter in Dongda water particles is mainly in the structure,Full degradation can explain this phenomenon.Sewage treatment plant tail water as an important part of the point source,the water samples in the visible-ultraviolet spectrum analysis found that the degree of humification has decreased.In the culture experiment,it was found that the stable and difficult to reduce the aromatic ring has increased.The molecular weight is basically maintained and the structural change is not significant.DOM in the class of fulvic acid-based,water stability is not easy to degrade.The peak position of fluorescence peak in the tail water during the 31-day culture of the sewage treatment plant did not change,and there were three strong peaks of peak A,peak B and peak D.Where the fluorescence intensity of A peak>D peak>B peak.The strongest peaks appear in the peak phosphoric acid peaks(UV fulvic-like,Ex/Em=230-270nm/360-470nm).The organic matter of the water body is mainly composed of refractory fulvic acid.Fourier transform infrared spectroscopy analysis showed that the organic matter in the tailings particulate matter of the sewage treatment plant was more complicated,and the intensity of the absorption band of the infrared spectrum was very low.The chemical bond remained stable and the organic matter was not easily degraded.The degradation of eggs in the sediment is rich in organic matter,UV spectroscopy,three-dimensional fluorescence spectra and infrared spectroscopy,and found that the unsaturated bond structure is the main,and the biochemical degradation reaction is carried out in the culture process.Due to the difference in COD composition,the degrading ability has the following characteristics:endogenous>agricultural surface source>urban surface source>point source.In contrast,the tailings of the sewage treatment plant are more difficult to degrade as a point source into the lake,which is easy to accumulate in the lake body,and the endogenous release and the agricultural nonphase source are relatively easy to degrade after entering the lake.The contribution of the accumulation of COD in the lake is relatively small.The contribution rates of endogenous,agricultural non-point source,urban non-point source and point source to Dianchi Lake were 15.73%,13.444%,40.72%and 30.106%,respectively,according to the degradation rate obtained in the culture experiment.The exogenous input is the main source of COD load in Dianchi Lake,accounting for 84.27%,of which the surface load is 54.165%.Urban non-point source accounted for a large,more than 40%.While the point source pollution COD load has the largest weight,that is,under the same conditions,the change of point source load has the greatest influence on COD.China’s lake governance emphasis on point source management,and point source control effect and the result is the discharge of tail water organic matter is difficult to degradation,such organic matter is easy to accumulate in poor water exchange lake.According to the experience of developed countries,such problems will gradually appear in our country,which is to ensure the lake water quality and long-term health and water supply all challenges.