| As a chemical detection technology for analysis of in-situ, real time and multiple materials, Laser Raman Spectroscopy is competent to take quantitative research for ingredients in ocean environment, and achieve long-term in-situ supervision of acid radical ionic concentration in seawater. It has great significance to detect and analyze submarine hydrothermal solution, earthquake source region and submarine sediment. Therefore, to develop the application of in-situ Laser Raman Spectroscopy in ocean research has become a scientific hotspot in various countries. However, "sensitivity" and "quantitative detection" are the existing challenges for this technology to be developed into reliable in-situ detection means. Aiming at the "quantification" key technical issues of Laser Raman Spectroscopy in marine in-situ detection, this thesis takes multiple marine environment factors into consideration and gives research on the in-situ quantitative and calibration methods that are appropriate for seawater acid radical ions Raman spectrum detection.In this thesis, we introduce the background and significance of this topic, as well as the fundamental principles of Laser Raman Spectroscopy, the evaluation criterion of quantitative and calibration analytical methods. Then we summarize its research status from the perspective of sensor development based on spectrum technology, and emphatically introduce relevant researches on spectrum quantitative and calibration methods. The chapter 3,4 and 5 of this thesis are the main part, including acid radical solution detection on a basis of deep-sea Laser Raman Spectroscopy system; pretreatment of Raman spectrum data, feasibility assessment of quantitative and calibration methods. Finally, the application of the quantitative and calibration methods in shallow-sea experiment will be displayed.This thesis uses the Laser Raman Spectroscopy system in laboratory that is based on observational network in seabed, taking single solution and mixed solution of SO42-,HCO3- and HS- with series of concentration to complete the Raman spectrum detection and spectrum analysis, which focuses on the fluorescent background, stochastic noises and peak overlaps of Raman spectrum. The pre-processing methods of spectrum data and The quantitative analytical method is explored. Original spectra are completed by peak finding of characteristic peaks, noise remove, background correction and feature extraction. Based on the pre-processing results, the veracity of concentration prediction of internal calibration method, partial least squares, and multiple linear regression is analyzed and compared in order to determine the optimal quantitative and calibrated method. The research indicates that combined with numerical differentiation, wavelet transform can be used to seek characteristic peaks, and the wavelet threshold method can be used to remove the noise, and the least square method can be used to correct backgrounds, and the Gaussian fitting method can extract the spectral signature. The application of multiple linear regression can effectively predict the 20 mmol/L HCO3- solution concentration and the SO42- concentration in the nearshore water in Qingdao. The fitting coefficient reaches as high as 0.951 and 0.992 with the relative error less than 6% and 5%.In order to get as accurately data of acid radical ions’ concentration in sea water as possible, the thesis conducts simulation study on the effect of water factor on Raman spectrum, and completes the quantitative analysis on the SO42- in the in-situ detection in shallow sea trials. The result indicates that the study results in this thesis can availably invert the tidal variation of the chlorophyll in offshore seawater during a day cycle in Nanjiang wharf of Qingdao, and effectively reduce the relative error of SO42- ration to 7.12%.At last, considering complicated physical, chemical and biological factors in ocean environment, this thesis puts forward further research plan and assumption. |
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