2.2. Plant growth experiment
A greenhouse pot trial was designed to test the growth of V. zizanioides and P. australis in Pb/Zn mine tailings and Cu mine tailings amended with manure compost, sewage sludge, and inorganic fertilizer. Sieved tailings, manure compost, and sewage sludge at predetermined ratios ( Table 1) were thoroughly mixed and subsequently placed in pots (17 cm in diameter and 20 cm in height) with a piece of 0.1 mm plastic sieve located at the bottom to retain the fine tailing particles. There were four replicates for each treatment. Tillers of V. zizanioides and P. australis were transplanted into the tailings. The pots were arranged in a randomized block design and watered daily in a greenhouse, and allowed to grow for 4 months. The temperature and relative humidity in the greenhouse were maintained at approximately 25 °C and 70% respectively. At harvest, the plants were carefully removed from the pots, washed thoroughly with tap water to remove any attached particles, and then rinsed 3 times with DI water, divided into aboveground and belowground parts (shoot and root), and freeze-dried to a constant weight.