Direct sensing of total alkalinity profile in a stratified lake Ghahraman Afshar et al. Direct sensing of total alkalinity profile in a stratified lake Figure S-1 Schematic illustration of the electrochemical cell. The proton pump was placed directly opposite the pH sensor while the thin layer sample gap was between the pH sensor and the proton pump. The counter electrode and reference electrode for the proton pump (not shown) were placed in the sample solution. The reference electrode for the pH sensor was also in the sample solution in the beaker. Figure S-1 Schematic illustration of the electrochemical cell. The proton pump was placed directly opposite the pH sensor while the thin layer sample gap was between the pH sensor and the proton pump. The counter electrode and reference electrode for the proton pump (not shown) were placed in the sample solution. The reference electrode for the pH sensor was also in the sample solution in the beaker. Ghahraman Afshar et al. (2017) Geochem. Persp. Let. 3, 85-93 | doi: 10.7185/geochemlet.1709 © 2017 European Association of Geochemistry