Investigate seawater and seawater anions' aqueous mixed solution by laser Raman spectroscopy

Da Teng; Jun Ma; Yangyu Huang; Xining Zhang; Ronger Zheng

doi:10.1117/12.757561

7 January 2008 Investigate seawater and seawater anions' aqueous mixed solution by laser Raman spectroscopy

Da Teng, Jun Ma, Yangyu Huang, Xining Zhang, Ronger Zheng

Proceedings Volume 6824, Semiconductor Lasers and Applications III; 68240P (2008) https://doi.org/10.1117/12.757561
Event: Photonics Asia 2007, 2007, Beijing, China

Abstract

Laser Raman Spectroscopy (LRS) is a proven and powerful technique in geochemical analyses, especially in the study of seawater and seafloor hydrothermal minerals anions, such as SO ₄^2-,CO₃^2-,HCO₃^-, etc. In our lab we have used LD pumped Nd:YAG Laser operating at 532 nm which is selected for its relatively efficient propagation through seawater to investigate the LRS of seawater, Na₂SO_4-NaHCO₃ and Na₂SO_4-Na₂CO₃ aqueous mixed solutions of different established concentrations. The sample is interrogated by a 532 nm laser and the Raman backscattering radiation passes through grating and is recorded on a CCD camera. In the Raman spectrum of seawater near Qingdao sea area, we find SO₄^2- symmetric stretching band centered at ~981 cm^-1 but neither CO₃^2- nor HCO₃^- signal could be observed . We have detected Raman spectra of mixed solutions and separated the Raman shift of anions from mixed Raman spectra, fitted the peak area and center with the method of the multi-peaks Gaussian Fit, then, used the ratios of the fitted areas (the ~981cm^-1 band in SO₄^2-, the ~1066cm^-1 band in CO₃^2- and ~1016cm^-1 band in HCO₃^-) and established concentrations to estimate the Raman cross-section rations. The results show Gaussian Fit can effectively separate the Raman shifts of anions in mixed solution which close to each other and conform to the single solution's in the released papers. And we obtain relative Raman cross-sections ratios [SEE MANUSCRIPT FOR EQUATION] are 2.52 and 3.88 respectively at excitation wavelength 532nm.

Citation Download Citation

Da Teng, Jun Ma, Yangyu Huang, Xining Zhang, and Ronger Zheng "Investigate seawater and seawater anions' aqueous mixed solution by laser Raman spectroscopy", Proc. SPIE 6824, Semiconductor Lasers and Applications III, 68240P (7 January 2008); https://doi.org/10.1117/12.757561

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