Orbetello - former Sitoco area

From the late nineteenth century mining and industry grew up around the lagoon: the manganiferous iron mines of Monte Argentario, worked from 1872-1874, and a sulphuric acid plant at Orbetello Scalo. In 1906 the chemical works later known as ex Sitoco came into operation, making fertilisers by treating raw materials with sulphuric acid produced from pyrite. The pyrite ash was piled around the works and in the adjoining lagoon, and used to build embankments. A dynamite and explosives factory was added in the 1930s. Sulphuric acid was no longer made from the 1970s; the mine closed in 1974 and the industrial activities between 1990 and 2006.

Characterisation found heavy metals widespread in soil, with pyrite ash in the «Bacini» area in front of the works (western lagoon). Groundwater contains manganese, iron and sulphates, for which ARPAT has also defined natural background values. In lagoon sediments heavy metals are widespread, with methylmercury in the eastern lagoon in front of the former Ferromin mine and below Ansedonia.