Fig. 6. (Bi)sulfite stability under varying simulated geochemical conditions.

a (Bi)sulfite stability under anoxic conditions and at pH values that encompass the range observed in MV2 and SJ3 springs. The mean percentage of SO₃²⁻ remaining 24 h after adding Na₂SO₃ to a concentration of ~50 µM is shown for triplicate microcosms prepared at each pH interval and incubated at 40 °C, while error bars show the standard deviation of the assays. b The effect of temperature and oxygen (20% O₂, 80% N₂) exposure on the stability of (bi)sulfite at pH 4. Microcosms were prepared and measured as in Fig. 6a, but at varying temperatures and with or without preparation under anoxic conditions.