2.2. Preparation of the zinc reduction column
The column was made of a length of Tygon® tubing (8 cm × 2.3 mm i.d.) filled with metallic zinc granules (0.15–0.40 mm), which were retained by disks of 25 μm nylon mesh (Swiss Screens (Aust) Pty Ltd., Huntingwood, NSW, Australia). Before use, the column was activated by flushing it with 0.1 mol L−1 hydrochloric acid at 2 mL min−1 for 3 min followed by 0.4 mg L−1 NO3−–N for 3 min at the same flow rate.