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[8] The injection consisted of the steady, 22 hr injection (at 100 mL min^-1) of a sodium bromide (NaBr) solution that had been dissolved in Everglades water that was filtered (0.2 µm) on site. Bromide was used as the solute tracer because of its conservative nature in Everglades water with circumneutral pH and a very low background concentration of Br (0.05 mg L^-1). The injection took place at a distance of 0.75 m upgradient of the upstream edge of vegetation in the experimental channel (Figure 2b). The tracer was introduced uniformly with depth and width across the channel by dividing the injection stream between four horizontally oriented soaker hoses (2.65 m long) that were spaced evenly with depth in the water column (Figure 2c). The distribution of the bromide tracer over the full depth of the surface water column distinguishes the design of this experiment from that of a companion experiment in which microscopic particles composed of TiO₂ were injected through a single soaker hose [Saiers et al., 2003].

[9] Bromide tracer concentration was monitored at a distance 6.8 m downstream of the injection beginning at the start of the injection and continuing for 48 hrs. Smallvolume (10 mL) water samples were collected in 20 mL plastic scintillation vials for Br analysis by applying suction to 1/8 inch stainless steel sampling tubes deployed throughout the water column and in the peat sediment to a depth of 30 cm. In surface water, the sampling tubes are designated as LS, LM, LD, CM, RS, RM, and RD, where L (left), C (center), and R (right) delineate lateral position in the channel (looking downstream) and refer to locations 0.9 m inside the left wall, at the channel center, and 0.9 m inside the right wall, respectively, and S (shallow), M (middepth), and D (deep) delineate vertical position and refer to depths of 15, 27.5, and 42.5 cm below the water surface, respectively (Figure 2c).

[10] Sampling tubes were also deployed in the peat sediment. These tubes were used to sample pore water of the floc (3 cm thick layer) and in the peat beneath the floc (approximately a 50 cm thick layer). Pore water was sampled from the following depths: 1.8, 4.3, 6.8, 9.3, 11.8, 20, and 30 cm below the surface of the floc layer (Figure 2c). Pore water sampling was conducted by very slow peristaltic pumping (1.5 mL min^-1) using a multichannel pump head following the design of Duff et al. [1998]. After the tracer experiment was completed, bromide concentrations in all samples were measured in the laboratory by ion chromatography with a detection limit of 0.02 mg L^-1, which easily allowed tracer concentrations to be distinguished from background concentrations of Br in surface water (0.05 mg L^-1) and in deeper pore water (0.18 mg L^-1).