Fig. 4
![Fig. 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40623-018-0919-0/MediaObjects/40623_2018_919_Fig4_HTML.png)
A short-term variation of gas concentration molar ratios on 12 January 2015. a CO2/SO2 molar ratio, b H2O/SO2 molar ratio, c SO2/H2S molar ratio, and d H2/SO2 molar ratio. Grey circles show ratios obtained for high concentration peaks of SO2 ≥ 10 ppm, and white circles are ratios of low concentration peaks of SO2 < 10ppm