Concentration levels of total and methylmercury in mussel samples collected along the coasts of Sardinia Island (Italy)

This paper reports the assessment of the total mercury (T-Hg) and methylmercury (MeHg) contamination of mussel samples collected by two sampling campaigns from along the coastline of Sardinia (Italy). T-Hg has been determined by a direct mercury analyser (DMA) whereas MeHg has been determined by gas chromatography–mass spectrometry (GC–MS) after acid extraction, and employs a novel NaBPh4 derivatization method. The evaluation of the quality of measurements was carried out by analysing candidate certified reference material (CRM) BCR 710, for MeHg and T-Hg, and CRM IAEA-350 for T-Hg. In the analysed samples, the T-Hg concentrations range from 35 to 115 (mu)g kg^-1 and from 40 to 830 (mu)g kg^-1, for the two sampling campaigns, respectively, whereas the MeHg concentrations range from l5 to 51 (mu)g kg^-1 and from 17 to 116 (mu)g kg^-1. Consequently, the MeHg/T-Hg ratios range from 0.33 to 0.91 and from 0.14 to 0.98, respectively. Despite the increasing trend of Hg concentration from the first to the second sampling campaign, the T-Hg concentration of all the samples was much below the 0.5 (mu)g g^-1 WHO limit, and the MeHg values ranged between 2.2 and 17.2 (mu)g kg^-1, not exceeding the 43.5 (mu)g kg^-1 tolerable daily residue level calculated for Italy.