Study On Optical Characteristics Of Dissolved Organic Matter In Water Of Typical Drainage Rivers In Tianjin

The spatial and temporal distribution,composition,and sources of Chromophoric Dissolved Organic Matter(CDOM)in water of Dagu Drainage River,Dagusha Channel,and Beitang Drainage River were analyzed by using UV-Vis and three-dimensional fluorescence spectroscopy.And,contrastive analyses were also made.In the end,FT-IR were used to analysis the functional groups.The main results were shown as follows:The CDOM absorption coefficient,a355,ranged from 3.80～82.60 m-1 in Dagu Drainage River,which was significantly higher than the natural water bodies and reflected the affects of sewage receiving.The high value ofa355 was concentreted on the downstream of the river,of which the value of a355 at D9 sites(Wannian Bridge)was always the highest.In Dagusha Channel,a355 ranged from 1.02～6.06 m-1,and it was lower than that in Dagu Drainage River,which mainly attributed to the dilution effect of the seawater.In Beitang Drainage River,a355 ranged from 2.43～20.97 m-1,falling in between Dagu Drainage River and Dagusha Channel.There were no same trends in the concentration of CDOM during sampling time in Dagu Drainage River,but it was fluctuated a lot in the downstream of the Dagu Drainage River;the concentration of CDOM in Dagusha Channel in autumn was higher than that in spring;the concentration distribution of CDOM in Beitang Drainage River exhibited a gradually decreased tendency during the periods of the survey,which meaned that the water quality maybe gradually improved.The UV-Vis spectrum parameter,E253/203,suggesting that the fulvic-acid accounted a larger proportion in humic-like substance in the study areas.Besides,E253/203 suggesting that the aromatic rings in CDOM were mainly replaced by—OH、—COOH、C=O、—COOR in the of downstream of Dagu Drainage River and B1 site.CDOM in water of the three areas contained protein-like(T1,T2)and humic-like components(A,C,M),In addition,B1 fluorescence peak also appeared in Beitang Drainage River.There were no obvious changes in the number and type of fluorescence peaks in all the sampings sites,except the intensity of the peaks.T1 was the highest in most of the sites,which indicated the impacts of human activities.The intensity of fluorescence peak A were the highest in the three humic-like components,which showed a larger proportion in humic-like substance in the study areas,and it was consistented with the conclusion of E250/365.The correlation analysis between fluorescence peaks and a355 showed that Tlwith T2,A with C and M were well related,which meaned a similarity in there compositions and sourecs.The significant correlation between A,C,M and a355,stating that the humic-like substances were the dominant composition in the lighting absorption of CDOM.The FT-IR spectrums of CDOM were similar to each other,which meaned that the composition of CDOM still had similarities on even with different sources.The main function groups of CDOM were—OH,—NH,C=O,C-O,Those reactive functional groups made CDOM in water environment more activated,can affect the migration of other pollutants in water.The correlation analysis between common water quality and optical parameters showed that the a355 and COD,T1 andTP,TN exhibited a good positive correlation.So optical tests can be used to replace chemical methods to estimate the COD,TP,TN of water in a environmernal,fast,real time way.