Field experimental studies of detecting the dissolved CO2/HCO-3 using Raman spectroscopy

NOTE: see pdf for symbols. The carbon in the ocean mainly remains in the system of the carbon dioxide and carbonate, the existence form of it including CO2,H2O3, HCO3−, CO2/3− and so on. pCO2 as the main parameter which need usually measured in the study of the system of the carbon dioxide and carbonate in the ocean, its mainly analysis methods is usually using infrared spectrum technology. In addition, about the HCO3 −dissolved in seawater, there is lacking of in-suit measurement equipment to study at present. Based on the above needs, in this paper, we using Raman spectroscopy technology to study the in-suit detection for the dissolved CO2 and HCO3- in seawater. We build a near-concentric cavity gas-liquid Raman spectroscopy combined detection system, the system mainly consists of the following three components: the detection optical of the gas, the detection optical of the liquid and the gas liquid separator. The field detection experimental took place in the Zhongyuan Wharf of Qingdao on December 1 ~ 2, 2016 (E 120.302° , S 36.053°). According to the analysis based on the results of the experiments, the Raman signal of N2 ,O2, CO2 and SO2/4−, HCO3− dissolved in seawater were detected in the trial, at the same time the fluorescence signal of CDOM(Colored Dissolved Organic Matter) and chlorophyll had also been detected with the same system. The field experiment results demonstrated that near-concentric cavity gas-liquid Raman spectroscopy combined detection system has great potential to study the system of carbon dioxide and carbonate in seawater. However, considering the ingredients of seawater is very complex and the effect of seawater (especially the interference from fluorescence matter), after further research on the sensitivity improved and data processing, it is hope to apply the system to the quantitative detection in seawater.