Form Distribution and Transformation of Pb in Composting of Pb-Polluted Lignocellulosic Waste with White-Rot Fungi

A major limitation of land application of compost is the potential heavy metal pollution, and lead (Pb) has been recognized as one of the most hazardous heavy metal. To reduce the hazards of Pb to the compost application, composting of Pb- polluted wastes by inoculating white-rot fungi was investigated. The parallel waste composting with no inoculants was performed as control. The form distribution and transformation of Pb during composting were discussed. Results showed that the active Pb ion was transformed into the inactive phase during composting. The soluble-exchangeable Pb with high toxicity in composting with white-rot fungi was reduced to 0 mg/kg dry weight compost at day 50, while that of the control only achieved 100.5 mg/kg till day 60. The higher content of organic-bound Pb (121.0 mg/kg) and residual Pb (141.9 mg/kg) with low toxicity was found after 60-day composting with white-rot fungi, compared to those in control. Meanwhile, the higher microbial biomass was observed in composting with white-rot fungi, and Pb concentrations correlated to the microbial biomass. All the results indicated that the method of composting with white-rot fungi reduced the transfer and bioavailability of Pb in compost so as to alleviate the potential stress of metal, and also improved the microbial growth.