Assessment of tin and butyltin species in estuarine superficial sediments from Gipuzkoa, Spain

Ten superficial sediments from river estuaries of Gipuzkoa (North Spain) were collected and analyzed for nine metals (including tin, Sn) and butyltin compounds (monobutyltin, MBT; dibutyltin, DBT; tributyltin, TBT). Total metal concentration in the fine fraction (<63 μm) of the sediment was determined in aqua regia––hydrofluoric acid extracts by atomic absorption spectrometry. The butyltin species (BTs) were firstly extracted from the sediments with hydrochloric acid–methanol mixture. After derivatization with sodium tetraethyl borate, the organotin compounds were extracted by solid phase microextraction (SPME) in headspace mode. A fiber coated with 100 μm poly(dimethylsiloxane) was used for SPME. The organotin species were analyzed by gas chromatography-flame ionization detection. Analysis of the certified reference sediment (PACS-2) shown the suitability of the procedures for determination of metal contents and DBT–TBT species in contaminated sediments. Factorial analysis was used to examine the main sources of metals. Three factors represented more than 89% of the total variance of the metal system, and the Sn was related with Cu–Zn–Pb suggesting the same pollution source. The BTs concentrations in the area were high (TBT ranged from 0.05 to 5.48 mg Sn kg−1). The percentage of total butyltin species (∑BTs) respect to the total Sn amount was higher than 4% in all the sediments, showing in the Bidasoa river estuary a remarkable value higher than 20%. Hence, the studied estuarine sediments reflect a pollution that is related with historical industrial and fishing activities of the area.