Study On The Influence Factors Of Fluorescence Determination Of Chlorophyll In The Water

Chlorophyll a which is contained in phytoplankton cells is an important index ofphytoplankton biomass and chlorophyll a content has the effect of risk early warning ofwater eutrophication, in addition, the content of chlorophyll a is also an importantparameter for pelagic fishery judgment. Currently the research and development ofon-line detection device of phytoplankton based on the chlorophyll a fluorometry hasbecome a research hotspots in the field of environmental monitoring.The principle of chlorophyll a fluorometry is that there is a linear relationship betweenthe fluorescence intensity of chlorophyll a excited by a specific light near440nm and theconcentration of phytoplankton within a certain range,so we can obtain the content ofphytoplankton biovolume by measuring the chlorophyll a fluorescence intensity.This paper summarized the research actuality of the determination method ofchlorophyll a in phytoplankton briefly, introduced the mechanism of fluorescencedetermination of chlorophyll a and the reseach progress of the main factors which affectthe intensity of the fluorescence. Established the new method of determination ofchlorophyll a in water with lab fluorometric method,and got the regression equationbetween concentration of chlorophyll a and fluorescence intensity wasy=307.41x+5.9809(R2=0.9983).The influence degree and influence mechanism oftemperature, turbidity, light intensity and pH on the determination was studied in detailand some experiments were carried out, tested the influence of the four environmentalfactors on measurement of phytoplankton by the On-line Detector for Water’chlorophyll.Conclusions are as follows:①the degradation rate of chlorophyll a increases withincreasing temperature, get the Temperature Coefficients of pure chlorophyll a,Scenedesmus obliquus,Chlorella pyrenoidosa and Microcystis aeruginosa areapproximate0.30%,1.09%,1.17%and1.14%respectively; in the field measurement whenthe ambient temperature within the scope of15℃~37℃it has little effect on theOn-line Detector for Water’chlorophyll and the measured values are acceptable;②whenthe water turbidity is large, due to the strong scattering effect of suspended particulatematter could make the chlorophyll a results determined by fluorometry are on the highside;③the synergy of light intensity×light time can cause light degradation ofchlorophyll a,and the design of light hood of the On-line Detector for Water’chlorophyll improves the accuracy and stability of the determination results to a great extent;④usually different water bodies have different pH, chlorophyll a is unstable and prone todegrade under the overly acidic or basic environment,therefore pH will have certaininfluence on chlorophyll a fluorescence determination results, determined the On-lineDetector’s best measurable pH range is6.0~9.5.