The PCB contamination in lower Fox River sediments was investigated in order to identify possible PCB sources, contributions, and transformations, using two receptor models. Congener specific sediment PCB data from sites immediately upstream of DePere dam to Green Bay that had been gathered for the Green Bay/Fox River Mass Balance Study, were used in this analysis. The first receptor model is a self training factor analysis (FA) model with non-negative constraints that was applied to identify the PCB sources and significant congener patterns. The second is a chemical mass balance model (CMB) in which published Aroclor sources, inferred from our FA model, were used to apportion these Aroclors to each sample. The FA model indicated two significant factors, the major one being Aroclor 1242 and the other, a profile dominated by low chlorinated congeners, indicating a possible PCB alteration profile. This profile had significant contributions to samples at or around sites with total PCB concentrations higher than 50 ppm, indicating a potential anaerobic dechlorination activity. It was also deduced from the FA model that very small contributions of more highly chlorinated Aroclors may be present in the system. The results from the CMB model confirmed that the system is dominated by Aroclor 1242. Its average contribution was 95%, with small amounts of Aroclor 1254 (2%) and 1260 (1%). Two of the samples, located in the vicinity of point sources, showed high contributions of Aroclor 1016 by the CMB model. This is interpreted as an altered Aroclor profile resembling the less chlorinated Aroclor 1016. Contributions obtained. form the CMB and FA models show similar patterns. (C) 2002 Elsevier Science Ltd. All rights reserved.