58
R. Ferrara
discovered accidentally around the year 1490. In the 17th and 18th centuries, the
Almaden mine (Spain) was closed as a consequence of numerous fires, and
mercury production was completely substituted by the Idrija mine. Mining
activity continued until 1977, with a total production of 150000 tons of mercury.
In 1983 mercury mining started to operate again but with a minimal production,
and was definitively terminated in the year 1994.
In the Idrija mine mercury is present both as native mercury (~30%), and in
minerals, mostly cinnabar (70%). The percentage of mercury in the rock was
around 10% in 1820 and then decreased to 0.6-0.7% in 1914. In about 500 years
of activity, 700 km of galleries have been dug, to a depth of 400 m (Kobal
1994).
At present and for about 10 years, 100 miners have worked in the mine and will
continue to do so to complete the work necessary for the closure of the mine.
Some galleries are being flooded with water, others are being backfilled with
gravel, to avoid the collapse of the hill, and to limit damage by environmental
contamination. Close control of the health state of these miners is operated by
Kobal and Dizdarevic (1996). The old miners' houses have disappeared like many
mine facilities (the stack of the furnace plant has been taken down). The Idrija
landscape is returning to its original state, thanks to the lack of roasted cinnabar
deposits: the roasted ore was used in the past for the building houses and streets,
while in recent times it was discharged into the river Idrijca that transported it,
through the Isonzo river to the Adriatic Sea, and in particular towards the coastal
area of Trieste.
Much interesting research has been carried out on the Idrija mine, but
unfortunately the results have often been published in local reviews or were
otherwise not available in the current literature (Kosta et a1. 1975; Kobal 1994;
Gnamus et a1. 1995). Recently, an excellent work was published by Palinkas et a1.
(1995) on the ecological impact of mining activity. A complete report of the
meeting on the research Idrija as a Natural and Anthropogenic Laboratory (in
which are reported numerous studies on geology, on mercury in the abiotic and
biotic compartment and on the effect of metal on the workers' health) is in the
final phase of preparation.
3.2
Main Sources of Atmospheric Mercury
During the period of greatest activity, the main emission source of mercury was
obviously the stack of the distillation plant which emitted 20 kg/day of mercury,
associated mainly with the atmospheric particulate matter. A second source was
made up by the two systems of ventilation of the galleries, at present still in
action, and around which a mercury concentration of the order of 2500 ng/m3
has been measured.
The emission of mercury from the ground, due to the presence of geogenic
cinnabar (and native mercury) has been increased by the enrichment caused by
the emission of the roasting plant.
R. Ferrara
discovered accidentally around the year 1490. In the 17th and 18th centuries, the
Almaden mine (Spain) was closed as a consequence of numerous fires, and
mercury production was completely substituted by the Idrija mine. Mining
activity continued until 1977, with a total production of 150000 tons of mercury.
In 1983 mercury mining started to operate again but with a minimal production,
and was definitively terminated in the year 1994.
In the Idrija mine mercury is present both as native mercury (~30%), and in
minerals, mostly cinnabar (70%). The percentage of mercury in the rock was
around 10% in 1820 and then decreased to 0.6-0.7% in 1914. In about 500 years
of activity, 700 km of galleries have been dug, to a depth of 400 m (Kobal
1994).
At present and for about 10 years, 100 miners have worked in the mine and will
continue to do so to complete the work necessary for the closure of the mine.
Some galleries are being flooded with water, others are being backfilled with
gravel, to avoid the collapse of the hill, and to limit damage by environmental
contamination. Close control of the health state of these miners is operated by
Kobal and Dizdarevic (1996). The old miners' houses have disappeared like many
mine facilities (the stack of the furnace plant has been taken down). The Idrija
landscape is returning to its original state, thanks to the lack of roasted cinnabar
deposits: the roasted ore was used in the past for the building houses and streets,
while in recent times it was discharged into the river Idrijca that transported it,
through the Isonzo river to the Adriatic Sea, and in particular towards the coastal
area of Trieste.
Much interesting research has been carried out on the Idrija mine, but
unfortunately the results have often been published in local reviews or were
otherwise not available in the current literature (Kosta et a1. 1975; Kobal 1994;
Gnamus et a1. 1995). Recently, an excellent work was published by Palinkas et a1.
(1995) on the ecological impact of mining activity. A complete report of the
meeting on the research Idrija as a Natural and Anthropogenic Laboratory (in
which are reported numerous studies on geology, on mercury in the abiotic and
biotic compartment and on the effect of metal on the workers' health) is in the
final phase of preparation.
3.2
Main Sources of Atmospheric Mercury
During the period of greatest activity, the main emission source of mercury was
obviously the stack of the distillation plant which emitted 20 kg/day of mercury,
associated mainly with the atmospheric particulate matter. A second source was
made up by the two systems of ventilation of the galleries, at present still in
action, and around which a mercury concentration of the order of 2500 ng/m3
has been measured.
The emission of mercury from the ground, due to the presence of geogenic
cinnabar (and native mercury) has been increased by the enrichment caused by
the emission of the roasting plant.