Fig. 2 Phase distribution of catechol-derived carbon as a function of time during reaction with birnessite in suspension at pH 4. Effects of second pulse of reactants [no additions (+0); catechol added (+C), birnessite added (+B) and both added (+BC)] at 5-h reaction time: (a) dissolved C; (b) solid-phase C; (c) CO₂ evolution. Initial and second pulse catechol concentrations each provided 13.8 mmol C L^-1. Initial and second pulse birnessite concentrations each provided 1.0 g L^-1. Standard deviations are indicated