Reserch On The System Used For Monitoring The Concentration Of Chlorophyll-a In Seawater In Realtime

With the rapid development of modern industry, a large number of industrialwastewater discharged into the sea without treatment , leading to the problem of marineeutrophication increasingly serious, the red tide which are caused by marineeutrophication has become a natural disasters faced by the global. Red tide is the result ofexplosive breeding of the algae under certain circumstances. Because of the content ofchlorophyll-a in seawater reflecting the number of photosynthesis, chlorophyll-aconcentration has become an important parameter of evaluating the nutritional level of thewater body. This passage made a study of one kind of ocean’s chlorophyll density systemwhich has a low power consumption and very portable. This system could complete thereal time online measurement.Firstly, the principle of fluorescence and the characteristic of the excitation andemission spectrum of chlorophyll-a are discussed in detail, while the principle offluorescence measurement method are analyzing selectively. The relationship betweenchlorophyll a concentration and fluorescence intensity can be deduced.Secondly, combined with the structural characteristics of the advanced foreignproducts, as well as the s small and portable design goals, optical system of fluorescencedetection is designed, which used LED and photodiode as the illuminant and photosensingdevice and selected interference filter with the same wavelength of fluorescence to filterstray light.Then, complete fluorescence detection and signal processing circuits are designed,including LED driver controlling module, Pre-filter amplifying module, analog to digitalconverting module and UART module, all the modules word orderly by softwarecontrolling. The principle of sampling integral method and how to extract the fluorescencesignal in the noise are discussed in detail.Ultimately, this passage monitored the absorption spectrum of chlorophylland fluorescence’s emission spectrum. Though measuring the Chlorophyll ethanol solutionin different drive current exciting light, linear diagrams between chlorophyll aconcentration and fluorescence intensity are drawn, then calculated both of their detection limit and lower detection limit. The analysis of measure result shows that it can effectiveraise the precision of measurement by modulating laser’s intensity in different density ofwater.