Thermal desorption for mercury removal from sediments sampled from the Adriatic sea

Overall sampling of the sediments in the Adriatic Sea at the mouth of the Isonzo (Soça) River in Italy has permitted updating of the extension and level of mercury contamination. The Isonzo River transports mercury-bearing residues from the Idrija mine (Slovenia), the area of which was contaminated during the mining of cinnabar (HgS). The mercury mine started operations in the 15th century and was shut-down finally in the 1980’s, due to the decreased demand for mercury. An attempt was made to remove mercury from the contaminated sediments by thermal desorption with the aim of ascertaining whether low temperature and short residence time could be suitable parameters for sediment clean-up if future needs should so require. The fact is that to date no studies have been made on the health of the Italian population living in the Gulf of Trieste area. Hence there is no known correlation between the anomalous mercury content of the sediments and symptoms attributable to the ingestion of even small quantities of mercury. Desorption time of about 20 to 30 min at temperatures varying from 325 to 350°C gave a residue with a mercury content below the limit imposed by Italian regulations for contaminated soils and sediments (5 ppm). The air and the mercury vapors driven off during roasting were treated before being released to the atmosphere.