Real-time analysis of multicomponent dissolved inorganic carbon in the air-sea exchanging process using gas-liquid Raman spectroscopy

Carbon cycle in coastal water is a significant dynamic component of global carbon budget , however, the diverse sources, carbon sinks and their complex interactions remained poorly understood. In order to detect the dissolved inorganic carbon (DIC) and their interactions, gas-liquid Raman spectroscopy was built and applied to simultaneously detect the constituents of air, dissolved CO 2 , HCO 3 - and chlorophyll in coastal water. The linear fitting curve between peak intensity and concentration was built for the quantitative analysis of HCO 3 - and CO 2 , meanwhile, the fluorescence peaks of chlorophyll at 679 nm were detected for the qualitative analysis. For the multi-components analysis, typical Raman spectra of the constituents of air, dissolved CO 2 , HCO 3 - in seawater, and the fluorescence spectra of chlorophyll in seawater were detected. Results showed that the time dependent change of CO 2 and O 2 in the air exhibited a contrary tendency, while that of dissolved CO 2 and O 2 was curved like a cosine. The changing tendency of relative concentrations of dissolved CO 2 was about 2 h earlier than CO 2 in air, due to the life activity of microorganisms driving the gas exchange at the air-sea interface. Furthermore, the study makes a study on the relationship between DIC and chlorophyll based on the detection of HCO 3 - and chlorophyll in coastal water, indicating that this gas-liquid Raman spectroscopy could successfully provide real-time analysis of multicomponent DIC in the air-sea exchanging process.