The sorption potential of octylphenol, a xenobiotic oestrogen, to suspended and bed-sediments collected from industrial and rural reaches of three English rivers

Laboratory batch techniques were used to study the sorptive behaviour of 4-t-octylphenol (OP), a xenobiotic with oestrogenic properties, to sediments from three English rivers of contrasting water quality. Samples were taken from industrially polluted lower reaches of the Aire and Calder rivers, in the Humber catchment, as well as a rural reach of the River Thames, in Oxfordshire in the South of England. The results showed that given either sufficient time or mixing, a large proportion of OP in solution will sorb to the bed-sediments, with distribution coefficients (Kd) of 6–700 l kg−1 and organic carbon normalised partition coefficients (Koc) 3500–18 000 l kg−1. The sediments which sorbed the highest quantities of OP had higher total organic carbon and a greater proportion of clay and silt particles. There was evidence in some bed-sediments of a sorption-desorption hysteresis effect between OP and sediment. The suspended sediments, on a carbon for carbon basis, adsorbed 5–35 times more OP than their respective bed-sediments in the Aire and Calder rivers: microscopic examination suggested that the suspended sediments were predominantly organic aggregates. The suspended sediments of the Thames adsorbed far less OP than those of the Aire and Calder: microscopic examination revealed these suspended sediments to be largely algae. The work predicts that suspended sediments may play a key role in the fate of OP in the industrial reaches of English Rivers. In the comparatively rural reach of the Thames, a higher proportion of OP might be predicted to remain free in solution.