Investigation of Two Novel Approaches for Detection of Sulfate Ion and Methane Dissolved in Sediment Pore Water Using Raman Spectroscopy

Sensors

Zengfeng Du²  Jing Chen²  Wangquan Ye²  Jinjia Guo²  Xin Zhang¹  Ronger Zheng² 

[1] Key Lab of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; E-Mail:;Optics and Optoelectronics Laboratory, Ocean University of China, Qingdao 266100, China; E-Mails:

关键词: Raman spectroscopy;    sulfate ion;    methane;    LCOF;    CCl₄ extraction;   

DOI  :  10.3390/s150612377

来源: mdpi

【 摘 要 】

The levels of dissolved sulfate and methane are crucial indicators in the geochemical analysis of pore water. Compositional analysis of pore water samples obtained from sea trials was conducted using Raman spectroscopy. It was found that the concentration of SO₄²⁻ in pore water samples decreases as the depth increases, while the expected Raman signal of methane has not been observed. A possible reason for this is that the methane escaped after sampling and the remaining concentration of methane is too low to be detected. To find more effective ways to analyze the composition of pore water, two novel approaches are proposed. One is based on Liquid Core Optical Fiber (LCOF) for detection of SO₄²⁻. The other one is an enrichment process for the detection of CH₄. With the aid of LCOF, the Raman signal of SO₄²⁻ is found to be enhanced over 10 times compared to that obtained by a conventional Raman setup. The enrichment process is also found to be effective in the investigation to the prepared sample of methane dissolved in water. By CCl₄ extraction, methane at a concentration below 1.14 mmol/L has been detected by conventional Raman spectroscopy. All the obtained results suggest that the approach proposed in this paper has great potential to be developed as a sensor for SO₄²⁻ and CH₄ detection in pore water.

【 授权许可】

CC BY   
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