Figure shows time courses of the concentrations Ci in an ORN in two cases where (a) only the final reaction products R43 to R49 are discharged from an ORN and (b) all reaction products R7 to R12 and R14 to R49 are discharged from an ORN. Figure all discharged reaction products are 5 × 10 -4 M, the initial concentrations of all chemical substances in an ORN are 1 × 10 -3 M, the kf is 0.6-1.1 M -1 s -1 , and the kf /kb is 1.4-2.6 in both (a) and (b), while the kdi is (0.94-1.0) × 10 -4 s -1 in (a) and (0.94-1.0) × 10 -5 s -1 in (b). Further details about the reaction conditions are given in the Supplementary Information. The reaction rate constant kf is chosen to be on the order of observed values, whereas kdi is taken to be much smaller than the observed values in a homogeneous solution on the basis of an assumption that the ORN is located at the bottom of a small, long pore and lies far from the primitive sea. Under these conditions, the rate of concentration change induced by reactions in an ORN is nearly equal to or slightly greater than that induced by inflows of source substances.