The abundance of perfluorooctanoic acid (PFOA) in the aquatic environment makes it important to understand the influence of important parameters affecting the partition of PFOA onto sediment. With a focus on the influence by dissolved organic matter (DOM), we investigated the sorption of PFOA to river sediment downstream of a semiconductor and optoelectronic industrial complex that discharged wastewater with a considerable amount of PFOA in it. The dominant components of the sediment were silica oxide (approximate to 14%) and iron oxide (approximate to 2%). The sorption density of PFOA was not significantly affected by solution pH and ionic strength. The combinations of low pH-high ionic strength and high pH-low ionic strength favored partitioning of PFOA to the sediment. The sorption density of PFOA to sediment ranged from 0.41 to 1.43 mu g/m(2), with the presence of DOM in the aqueous phase reducing the affinity of PFOA toward the sediment. The sorption of PFOA seemed to be facilitated not by electrostatic but by hydrophobic interactions. The PFOA-sediment sorption equilibration required a duration exceeding 12 d. This study revealed DOM as an important solution-specific parameter in sorption studies. The influence of DOM on PFOA sorption provides a useful reference to understand PFOA partition in the aqueous environment. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the free supplemental file.