Arsenic in mining environments: evidences from Sardinia (Italy)

In Sardinia, the dispersion of arsenic in the environment appears strictly linked with mineralised bodies and mining activities. Currently, the areas of main concern are the active gold mine at Furtei, and the abandoned Pb- As mine at Baccu Locci. At Furtei, the main sources of arsenic are enargite, and arsenian pyrite; an ongoing monitoring program of water quality in the area around the mine documented so far no major changes with respect to pre-mine conditions, except for the formation of extremely acid, As-rich pit lakes. At Baccu Locci, the main primary source is arsenopyrite; arsenic dispersion is essentially due to the past unwise practice of discarding mine tailings into the nearby creek. Arsenic is slowly released from residual arsenopyrite and temporary secondary mineral traps such as Fe-oxyhydroxides, causing contamination of soils and waters as far as 10 km downstream of the mine

AMD generation from dissolution of secondary metal sulphates

Melanterite (Fe²⁺SO₄·7H₂O) is one of the most common oxidation products of pyrite. Field observations in mine sites indicate that melanterite is associated with acidic waters. However, simple dissolution of melanterite, without oxidation of Fe2+ to Fe3+, can not generate AMD because the hydrolysis of Fe2+ is not able to significantly lower the water pH. Laboratory dissolution experiments modelled with PHREEQC have shown that trace amounts of Fe3+ contained in melanterite in the range of 0.16—0.20 wt.% are sufficient to significantly lower the pH of very dilute interacting waters as a consequence of Fe3+ hydrolysis. In the field, the rapid dissolution of Fe3+ -bearing melanterite by rain water may thus generate AMD and also provide a supply of Fe3+ for subsequent sulphide oxidation. These results should be taken into account when evaluating the impact of AMD on the environment and planning its treatment

Preliminary assessment of water quality in the Rio Mannu di Narcao basin (Sardinia, Italy)

the quality of surface water and groundwater in the rio Mannu di narcao basin was investigated as a part of the characterization plan of the area, a preliminary study before undertaking a project to mitigate the impact of past mining. Dissolved Zn, cd and Pb contents allow to circumscribe the risk source to a restricted area and to identify the origin of this contamination in the water flowing from an adit. on the contrary, as contamination originates by the interaction of stream water with as-rich fine materials originally deposited along the banks and now eroded and transported into the river bed

The abandoned mining area of Montevecchio-Ingurtosu

The Montevecchio-Ingurtosu area (Sardinia SW) was one of the most important mining districts for Pb and Zn in Sardinia. For its very important cultural and industrial heritage this area, located in a natural context of scenic beauty, is included in the Geo-mining Park of Sardinia, sponsored by the Unesco. The field trip included the visit of fascinating examples of industrial archeology (Piccalinna plants and the village of Montevecchio) and areas where the natural environment is degraded by mine wastes weathering (Casargiu stope and Rio Naracauli). The field trip ran in a natural context of spectacular beauty in front of the Mediterranean Sea (giant sand dunes and the woody habitat of Sardinian deer, a rare endemic species)