Inversion Of MC-LR Concentration Of Microcystin Based On Characteristic Components Of Extracellular Organic Matter

Microcystin(MC-LR)is a potential carcinogen released during the growth and metabolism of cyanobacteria.It enters the human liver through oral and bio-enrichment,which seriously endangers human health.At present,conventional water treatment processes do not stably and efficiently reduce the concentration of MC-LR in water.Therefore,in order to ensure the safety of drinking water,it is necessary to carry out real-time online monitoring and early warning of MC-LR concentration.In this paper,three-dimensional fluorescence spectroscopy and parallel factor analysis(PARAFAC)were used to analyze the components of extracellular organic compounds(EOM)of Microcystis aeruginosa cultured in laboratory and in Lake Taihu.At the same time,the dynamic correlation between the biomass of algae cells,EOM components and MC-LR release concentration was explored,the characteristic components of EOM which are highly correlated with MC-LR concentration are screened out,and the MC-LR concentration inversion equation based on characteristic components of EOM was established.Relevant conclusions are as follows:1.The three-dimensional fluorescence spectra of dEOM(dissolved extracellular organic matter)and bEOM(bound extracellular organic matter)of Microcystis aeruginosa cultured in laboratory,which have four distinct fluorescence peaks:low excitation wavelength tryptophan-like fluorescence peak S,high excitation wavelength tryptophan-like fluorescence peak T,humus-like fluorescence peak A and C in ultraviolet and visible regions,four fluorescence peaks in the three-dimensional fluorescence spectra of Microcystis aeruginosa dEOM during the outbreak of algal blooms in Taihu Lake are identical with them,but in the three-dimensional fluorescence spectra of bEOM,besides the fluorescence peaks T,A and C,there are also tyrosine-like fluorescence peaks D.2.Principal component analysis showed that the fluorescence peaks S and T in dEOM and bEOM cultured in laboratory represent the same kind of protein,while fluorescence peaks A and C represent the same kind of humus.Fluorescence peaks A and C in dEOM and bEOM of Taihu Lake represent the same species of humus.The fluorescence peaks S and T of dEOM can be classified as protein-like,but their sources are not unique.The fluorescence peaks D and T of bEOM belong to the characteristic peaks of protein-like,but can not be classified as one.3.PARAFAC analysis showed that dEOM of Microcystis aeruginosa cultured in laboratory could be divided into three components:component 1 is tryptophan-like,component 2 is humus-like and component 3 is protein-like.bEOM can be divided into two components,protein-like and humus-like.The dEOM and bEOM of Microcystis aeruginosa in Lake Taihu can be divided into three components.The dEOM components 1,2 and 3 are protein-like,humus-like and tryptophan-like respectively,the bEOM components 1,2 and 3 are tyrosine-like,protein-like and humus-like respectively.At the same time,the intensity of fluorescence peaks of dEOM and bEOM was significantly correlated with the score of corresponding components of EOM,and the variation rules were similar.The change in intensity of each fluorescent peak can basically reflect the change in the content of each component of the corresponding EOM.In particular,the fluorescence peaks A and C have a correlation coefficient between the fluorescence intensity and the humus-like component scores close to 1,and the variation rules are identical.4.The correlation analysis between MC-LR concentration and algae cell biomass showed that the overall correlation coefficient between the biomass of Microcystis aeruginosa cultured in laboratory and MC-LR concentration was 0.433.In stable stage,pre-decay stage and decay stage,the biomass of algae cells was significantly correlated with the concentration of MC-LR,and the correlation coefficients were 0.839,0.512,and 0.680,respectively.Correlation coefficient between chlorophyll a concentration and MC-LR concentration was only 0.174 during the outbreak period of Lake Taihu.Therefore,the inversion of MC-LR concentration in real water by algae cell biomass is unreliable.5.For laboratory-cultured Microcystis aeruginosa,the release ability of EOM components and MC-LR from algae cells was significantly correlated during the stable and declining stages.For Microcystis aeruginosa in Lake Taihu,the intensity of normalized fluorescence peaks of chlorophyll a EOM is similar to that of MC-LR.According to the correlation between fluorescence intensity and MC-LR,the fluorescence peaks D,T,C of dEOM fluorescence peaks were significantly correlated with the concentration of MC-LR,and the correlation coefficient was between 0.462 and 0.815.It can be used as a characteristic component of MC-LR concentration inversion.6.The inversion MC-LR concentration linear regression equation based on characteristic components of EOM was established.The inversion effect of the regression equation is evaluated by three indexes:the determination coefficient,the root mean square error and the root mean square relative error.The results showed that the inversion effect of fluorescence peak T of bEOM was the best.Regression coefficient was relatively concentrated in different chlorophyll a concentration ranges.The determination coefficient R2 was 0.841,the root mean square error was 0.579?g·L-1,and the root mean square relative error was 37.10%.In summary,the regularity of variation between the normalized characteristic components of EOM and MC-LR concentration is similar by chlorophyll a,The algae cells showed a significant correlation with their release capacity,and the inversion linear regression equation constructed by characteristic components of EOM obtained a good inversion effect.Therefore,a method for inverting the concentration of MC-LR based on the characteristic component of EOM of Microcystis aeruginosa is feasible.