The extraction reagents examined were citratedithionite-bicarbonate, ammonium oxalate-oxalic acid, hydroxylamine hydrochloride, calcium nitrilotriacetic acid, and acetate-tartrate. This extraction procedure was included in an extraction sequence which differentiated the exchangeable phosphorus and iron fraction, the iron hydroxides and associated phosphorus, and the organic phosphorus and lithogenous iron. The ratio of mercury in sediment/mercury in water increased with increasing salinity of the estuary water. Mercury fixes most on suspensions in the surface water, as these suspensions comprise smaller particles. Itoh et al. have developed an automated flow system to eliminate interferences from transition metal ions during the hydride generation/atomic absorption spectrometric determination of selenium in estuarine sediments. Sinex et al. have evaluated the accuracy and precision of a method for the determination of chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium and lead in estuarine sediments. Systematic errors occurred in analysis of lanthanum, cerium and zirconium.