Study On In-Situ Fluorescence Detection Technique Of Chlorophyll A

The algae and phytoplankton contained in the ocean are an important material basis to support the normal operation of the earth’s ecological cycle system,and their distribution,content and dynamic changes in time and space in the ocean are the scientific issues to study the level of marine primary productivity and marine eutrophication.With the acceleration of human urbanization,a large amount of industrial and domestic wastewater is discharged,resulting in frequent outbreaks of red tides and other phenomena in the ocean and tending to normalize.Marine workers in various countries are seeking effective monitoring methods for the marine ecological environment,in order to better provide strategies and early warnings for marine management.At present,the concentration of chlorophyll a and its temporal and spatial distribution can reflect the growth status of algae and the level of primary marine productivity.Besides,they are also the most direct indicators for monitoring and early warning of red tides.Therefore,it is necessary to develop an in-situ marine chlorophyll a sensor with high precision,real-time,and long-term monitoring characteristics.This thesis comprehensively analyzes the current research status and technical characteristics of chlorophyll a sensor at home and abroad.According to the practical application requirements of chlorophyll a in-situ detection,the marine in-situ chlorophyll fluorescence detection device is designed and developed by fluorescence analysis method.The main contents are as follows:1.The key optical components of the chlorophyll fluorescence detection device are designed based on the coaxial optical path.The achromatic lens is used at the front end to improve the fluorescence detection efficiency,and the separation of the excitation light and the fluorescence detection is realized through dichroic mirror,which reduces the complexity of the optical path assembly and mechanical structure.Based on the optical path structure,the pressure-resistant packaging design and prototype assembly of the system are completed.2.The hardware circuit and software acquisition system for chlorophyll fluorescence detection based on STM32 are developed.The hardware part adopts a two-stage operational amplifier design,and uses a high-precision A/D conversion chip to achieve low-noise and highprecision chlorophyll a fluorescence detection.Based on self-adaptive gain technology,the detection range of chlorophyll a concentration is expanded while taking into account the detection accuracy of the instrument.On this basis,the computer software acquisition system is developed,which can realize in-situ real-time chlorophyll a concentration data acquisition.3.The instrumental chlorophyll a linearity and detection range were tested in the laboratory.It is determined that the detection range of the developed in-situ chlorophyll a sensor system is 0～50 μg/L.In response to the needs of in-situ detection,a 24-hour pressure resistance test is completed in the pool of the National Deep Sea Base Management Center.4.The field performance test of the instrument is carried out.The concentration of chlorophyll a at different time periods and temperatures is tested,and the variation of chlorophyll a concentration is obtained.Besides,this work accumulates experience for later application tests in marine environment.