Study On The In Situ Classified Determining Methods For Water Phytoplankton Concentration And Design Of A Monitoring System

Eutrophication causes excess proliferation of phytoplankton in water and usually brings into water bloom and red tide,which greatly damages to human health and sustainable development of economy.Real time,on line and classified determination of phytoplankton concentration is the basis of early alarming of water bloom and red tide.However,proper determining methods and instruments which can be used for real time,on line and classified determination of phytoplankton concentration are not available.Therefore,based on in vivo fluorescence spectra,classified determining methods of phytoplankton concentration were studied and a phytoplankton fluorometry which can be used for real time,on line and classified determination of phytoplankton concentration was designed in this dissertation.In vivo three dimensional excitation-emission fluorescence spectra and excitation fluorescence spectra of 16 species of phytoplankton which are dominant in eutrophic fresh water were studied.Fresh water phytoplankton were divided into three spectra groups according to the in vivo fluorescence spectra characteristics, which are blue group,green group and brown group.Due to the fact that nearly all of the phytoplankton in freshwater which release toxins are included in the blue group, the above spectral classification realized the differentiation of the phytoplankton which release toxins and those which do not release toxins.Based on the spectral classification,in this dissertation three classified determining methods for phytoplankton concentration were put forward.The first one is based on three dimensional excitation-emission fluorescence spectra and PARAFAC model,the second one is based on excitation fluorescence spectra and multivariate linear regression,and the third one is based on the characteristic excitation fluorescence wavelength band and multivariate linear regression.The analysis results of mixed phytoplankton cultures which are prepared in laboratory proved the feasibility of the three classified determining methods.According to the principle of the classified determining method which is based on the characteristic excitation fluorescence wavelength band,another classified determining method for phytoplankton concentration using multi-wavelength LEDs as excitation light source was further put forward.Based on the determining method, a phytoplankton fluorometry which used multi-wavelength LED array as excitation light source was designed.With the phytoplankton fluorometry,real time,on line and classified determination of phytoplankton concentration can be realized.The entire design idea for the fluorometry and the design scheme for the hardware and software were detailed introduced.The measurement performance of the fluorometry was analyzed by the determination experiments for the phytoplankton cultures which were prepared in laboratory.Total chlorophyll a concentration and chlorophyll a concentration of three spectra groups of 20 sites in western Chaohu lake were determined by the phytoplankton fluorometry.Meanwhile total chlorophyll a concentration and chlorophyll a concentration of three spectra groups were measured by spectrophotometer method and marker pigment HPLC method in laboratory respectively.The results show that total chlorophyll a concentration determined by phytoplankton fluorometry has a good linear relationship with that determined by spectrophotometer method,the linear correlation coefficient is 0.93861.The linear correlation coefficients for chlorophyll a concentration of blue group,green group and brown group determined by phytoplankton fluorometry and those determined by marker pigment HPLC method were 0.79158,0.97896 and 0.58063 respectively.The field experiment results proved the reliability of the phytoplankton fluorometry in practical application.