Analysis of poly(vinyl chloride) and other polymers in sediments and suspended matter of a coastal lagoon by pyrolysis-gas chromatography-mass spectrometry Original Research Article

Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was used for the analysis of synthetic polymers in core sediments and suspended particulate matter (SPM) of the coastal lagoon Pialassa Baiona (Adriatic Sea). Pyrograms exhibited a multitude of peaks deriving from the thermal degradation of natural organic matter (humic substances, planktonic material), artificial resins and synthetic rubbers. Upon pyrolysis, sediments generated high levels of styrene and benzene and a series of aromatic hydrocarbons (α-methylstyrene, indene, naphthalenes, biphenyl, diphenylpropane) indicative of the presence of vinyl polymers (e.g. poly(vinyl chloride), polystyrene), whereas markers for rubbers (butadiene dimer, styrene-butadiene) were identified in pyrograms of SPM. Concentrations of styrene polymers (expressed as polystyrene, PS) and poly(vinyl chloride) (PVC) were estimated in sediment cores by Py-GC-MS using the evolved benzene and styrene for quantitation, and values greater than 1 mg/g were observed in the most polluted layers. Plastic materials were isolated from sediments by Soxhlet-extraction with dichloromethane followed by precipitation in n-hexane and analysed by Py-GC-MS and spectroscopic techniques (1H- and 13C-NMR spectroscopy, FTIR). PVC made up the bulk of the isolated polymers which were found at concentrations up to 55 mg/g. PVC concentrations determined by both methods (direct pyrolysis and polymer extraction), showed maxima in subsurface strata and were strongly correlated with Hg concentrations. This finding suggests that the presence of resins is due to past industrial activity, even though the identification of styrene-plastic rubbers in SPM indicates that polymers are still redistributed and/or discharged into the lagoon.