Fig. 5. Relative Br^- and cell concentrations and water contents for the two variable unsaturated flow columns (a and b). The average residence time for one pore volume was 8.13 h for Column A and 11.9 h for Column B. Both columns had 12-h cycles of inflow, but the pore volumes per cycle differed between columns due to differences in flow rate and water content (Table 1)