Evolution properties and dechlorination capacities of particulate organic matter from a landfill.

• The landfill-derived POM comprised protein-, fulvic-, and humic-like substances. • The POM contains hydroxyl, carboxyl and quinone functional groups. • The EDC of the landfill POM was higher than its EAC. • The intermediate and old POM promoted dechlorination of PCP more effectively. Particulate organic matter (POM) includes humin and non-degradable residues, and the knowledge about its composition, evolution and environmental behavior is limited. The composition, evolution and its influence on dechlorination of the POM in landfill was studied. The results show that POM accounts for 27 %–57 % of the organic matter in landfill cell, which is mainly composed of protein-, fulvic- and humic-like components. Firmicutes and Proteobacteria were the main microorganisms driving the compositional evolution of POM during the landfilling process. The electron acceptance capacities (EAC) and electron donating capacities (EDC) of POM were in the range of 0.05–0.51 μmol/gC−1 and 0.13–0.66 μmol/gC−1, respectively, and the average EAC and EDC of POM in the intermediate and old stage of landfill were higher than those in the initial stage. The combined action of MR-1 and POM increased the degradation rate of PCP by 20 %–40 %, which was ascribed to the reduction capacities and electron transfer process of POM. POM derived from the intermediate and old stages promoted PCP dechlorination more effectively when compared with the initial stage due to its high electron transfer capacities (ETC), which are of great significance for soil in-situ bioremediation. [ABSTRACT FROM AUTHOR]