3. Results
3.1. General properties of the tailings, manure compost and sewage sludge
The general properties of the Pb/Zn and Cu mine tailings, manure compost, and sewage sludge are presented in Table 2. The Pb/Zn tailings were near neutral (pH 7.43), while the Cu tailings were alkaline (pH 8.93). The manure compost and sewage sludge were acidic (pH 4.02 and 5.90 respectively). The EC values of the Pb/Zn and Cu tailings were low (1.77 and 0.20 mS/cm), while those of the manure compost and sewage sludge were high (8.59 and 16.0 mS/cm respectively). The total and DTPA-extractable Pb and Zn contents of the Pb/Zn tailings were high, and the total Cu content was high (1084 mg/kg) in the Cu tailings, with a high content of DTPA-extractable Cu, but only a small proportion of these elements could be extracted by water. The total and water-soluble N, P, and K contents of the Pb/Zn and Cu tailings were extremely low or even undetectable, while the manure compost and sewage sludge contained high levels of total N and P. However, the manure compost contained higher concentrations of water-soluble P and lower water-soluble N, but the situation was reversed in the sewage sludge. The manure compost and sewage sludge contained higher total organic carbon contents (49.6% and 42.9% respectively), while the Pb/Zn and Cu mine tailings contained a very low level of total carbon (0.67% and 0.23% respectively). In addition, both the manure compost and sewage sludge contained relatively high DTPA-extractable Cu and Zn.