Research On Mercury Concentration Measurement System Based On Ultraviolet Fluorescence Method

With the development of the economy and the productivity in the whole world,the problem of environmental pollution has aroused more and more attention.Mercury is a global pollutant due to its instability,easily diffusion and biological enrichment.The main cause of mercury pollution is the emission of man-made factors,and the most important of which is the combustion of coal.In the whole world,the mercury pollution is particularly serious in our country.Currently there is no reliable monitoring system of power plant flue gas mercury emissions and the monitoring of total mercury in domestic coal-fired power plant flue gas is still a blank.Therefore,the research on the continuous monitoring method of total mercury is of great significance to the development of the total mercury emission limit of the power plant in China.At present,there are several principles for measuring the concentration of multi-phase mercury: cold vapor atomic absorption spectrometry(CVAAS),cold atomic fluorescence spectrometry(CVAFS)and atomic emission spectrometry(AES).Among the above ways,atomic fluorescence spectrometry method has very high superiority because of high sensitivity,low detection limit and basically no interference.This paper is a research based on the ultraviolet fluorescence spectrometry measurement to establish mercury concentration measurement system.The main work and results are as follows:(1)The preparation method research of the standard mercury solution in various orders of magnitude of concentration.Because the ppb level of mercury solution is extremely unstable,so the protective agent should be added in solution during the period of preparation and storage to prevent loss.After the full study and a large number of experiments,the ideal solution for the preparation of mercury standard solution was determined.(2)To determine the experiment scheme for the reduction of mercury standard solution.The formulation of the scheme determines the rationality and accuracy of the reaction results.Under the influence of the experimental system and the experimental conditions,a set of experimental system for the reduction reaction of mercury solution is determined.(3)Development of atomic fluorescence mercury measurement system.The independent design of excitation light source-darkroom system and internal cycling of mercury vapor generating device has been successfully developed into a high sensitive atomic fluorescence mercury measurement system.The system has the advantages of high sensitivity,low detection limit,simple sample pretreatment and so on.It can realize the direct determination of ultra-trace mercury in liquid sample.Independent design of the internal cycle-the dual mode of operation,not only has the advantages of safe and efficient,but also can provide a high accuracy and closure.Darkroom-excitation light source system not only can ensure the laboratory personnel's physical safety,but also can effectively reduce the light loss during transmission,eliminating the interference of stray light.(4)Use the atomic fluorescence mercury measurement system to determine ultra-trace mercury concentration in liquid phase.Use the atomic fluorescence mercury measurement system to do a series of experiments to determine the optimized experimental conditions,and successfully determined the ultra-trace mercury concentration in pure water,tap water and surface water in Beijing Haidian under the optimized conditions.The results show that the measurement system can be applied to the measurement of ultra-trace mercury in water.Then through the Ontario method to do field sampling measurement in Zhangjiakou Shalingzi power plant.Compare the results with LUMEX measurement results to see there is no significant difference between the results,which shows that the measurement system's effect in the practical application,and then analyze the measurement results.