Effects of paper sludge addition on the bioavailability and distribution of Pb in contaminated soil

Heavy metal contamination of soil poses risks and hazards to environment and human being. Many amendments were used to remediate the contaminated soil. In this report, paper sludge was used to reduce the bioavailability of Pb in soil, and the remediation mechanism was studied by investigating the redistribution of Pb speciation after paper sludge addition. In pot experiments, significantly increased weights of shoots (from 1.6 to 3.3 mg per plant) and roots (from 0.7 to 0.8 mg per plant), as well as significantly decreased Pb content in shoots (from 153.8 to 24.4 mg kg(-1)) and roots (from 467.1 to 38.0 mg kg(-1)) of rape were observed after paper sludge was added. The addition of paper sludge resulted in redistribution of Pb from the liable fractions (carbonate-bound Pb from 58.3 to 3.7%) to the Fe-Mn oxide-bound fraction (from 29.2 to 74.9%). Paper sludge addition increased the content of organic matters and pH of soil, and induced Pb redistribution, which ultimately inhibited Pb uptake and improved plant growth.