To investigate the feasibility of using biochar to control organic pollutants in sediments, we extracted biochar from rice-straw combustion residues (RBC) and studied its adsorption ability and effect on seed germination ecotoxicity of pentachlorophenol (PCP). The results showed that the Freundlich and dual-mode models could describe all the sorption isotherm data well, and the log K(OC) values increased with increasing RBC content. With 50 mg kg(-1) PCP in the sediment, a significant seed growth inhibition (P < 0.01) was observed. The addition of 2.0% RBC lowered the PCP concentration in the extraction liquid from 4.53 to 0.17 mg L(-1) and increased the germination rate and root length significantly. Furthermore, it was found that the addition of RBC had no toxic but stimulative effect on root elongation. Consequently. RBC could serve as a potential supersorbent for the remediation of organic pollution in situ. (C) 2010 Elsevier Ltd. All rights reserved.