Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has been applied to study the composition of synthetic polymers in sediments and nepheloid layers of Pialassa Baiona, a coastal lagoon located north-east the city of Ravenna (Italy), in the proximity of an industrial area. To this purpose sample pyrograms are compared with pyrograms of standard synthetic polymers, namely poly(vinyl chloride) (PVC), poly(vinyl acetate) (PVA), polystyrene (PS), polybutadiene (PB), poly(acrylonitrile-co -styrene-co -butadiene)(ABS), styrene-butadiene random (SBR) and block (SBS) copolymers. The presence of synthetic polymers in environmental samples is indicated by anomalous high levels of styrene and benzene in the pyrograms, and by the detection of selected markers (e.g. chlorobenzene for PVC, acetic acid for PVA, benzenebutanenitrile for ABS, cyclohexenylbenzene for styrenebutadiene rubbers), which are useful for a better identification of individual polymers. The occurrence of polymers in the solid phase collected in surface and bottom waters is discussed in connection with the presence of mercury, another major pollutant of the lagoon. (C) 2001 Elsevier Science B.V. All rights reserved.