Mercury Mines in Europe
61
3.5
Mercury in the Sediment
Stream sediment (active sediment from the stream bed in regular contact with
stream water) was sampled by Gosar et al. (in press) in July 1991 and 1995 along
the Idrijca and Soca rivers.
Due to the fast flow of the water of the Idrijca river, a large part of polluted
sediments is carried downstream towards the river Soca and finally into the
Adriatic Sea (Kosta et al. 1975). The amount of mercury in the region from Idrija
to Spodnja Idrija is rather high (300-1000 mg/kg). Downstream, from Spodnja
Idrija on, the sediments contain less mercury (S-300 mg/kg).
Overbank (floodplain) sediment is produced when major floods occur in a
river system, and can reach a thickness of up to a few metres. A vertical section of
this sediment reflects the history of sedimentation back through time. A sample
of recent overbank presents a mercury concentration of 120 mg/kg in the upper
part of the profile and reaches a value of 240 mg/kg at the depth of 80 cm; then
the concentration decreases again to around 120 mg/kg. The increasing
concentration of mercury is probably due to the different production levels of
the mining and the smelter. The profile was not deep enough to reach the
deposits present before the beginning of the mining activity.
3.6
Mercury in the Springs and River Water
Mercury levels (10-31 ng/l) have been determined at five springs (used for the
municipal water supply system), of which four are in the town and one is the
spring of the Idrijca river.
The data reported for 16 sites (7 km upstream, 18 km downstream, and in the
mining area) show extremely low concentration (3-20 ng!l); Palinkas et al. (199S)
believe that these low values are due to the high pH (7.S-8.3) of well-buffered
waters, a characteristic of karst hydrology.
3.7
Mercury in the Biota
In 1992 Lupsina et al. published a review on the total mercury and methylmercury in a species of epiphyte lichen (Hypogymnia physodes L. Nyl.) sampled in an
area which also included Idrija. The highest mercury concentration was found
near the smelting house (uS-188 ~lg/g d.w.), in comparison with the areas in the
centre of Idrija (17-48 ~lg/g) and the surrounding area (2-7 ~lg/g). The lowest
concentration was found at the control site in a mountain area (0.4 ~lg/g).
According to the findings of others workers (Bargagli et al. 1987), a good
correlation was found by the authors between mercury in the air and lichens. The
fraction of methylmercury varied from 0.06 to 3.7%.
61
3.5
Mercury in the Sediment
Stream sediment (active sediment from the stream bed in regular contact with
stream water) was sampled by Gosar et al. (in press) in July 1991 and 1995 along
the Idrijca and Soca rivers.
Due to the fast flow of the water of the Idrijca river, a large part of polluted
sediments is carried downstream towards the river Soca and finally into the
Adriatic Sea (Kosta et al. 1975). The amount of mercury in the region from Idrija
to Spodnja Idrija is rather high (300-1000 mg/kg). Downstream, from Spodnja
Idrija on, the sediments contain less mercury (S-300 mg/kg).
Overbank (floodplain) sediment is produced when major floods occur in a
river system, and can reach a thickness of up to a few metres. A vertical section of
this sediment reflects the history of sedimentation back through time. A sample
of recent overbank presents a mercury concentration of 120 mg/kg in the upper
part of the profile and reaches a value of 240 mg/kg at the depth of 80 cm; then
the concentration decreases again to around 120 mg/kg. The increasing
concentration of mercury is probably due to the different production levels of
the mining and the smelter. The profile was not deep enough to reach the
deposits present before the beginning of the mining activity.
3.6
Mercury in the Springs and River Water
Mercury levels (10-31 ng/l) have been determined at five springs (used for the
municipal water supply system), of which four are in the town and one is the
spring of the Idrijca river.
The data reported for 16 sites (7 km upstream, 18 km downstream, and in the
mining area) show extremely low concentration (3-20 ng!l); Palinkas et al. (199S)
believe that these low values are due to the high pH (7.S-8.3) of well-buffered
waters, a characteristic of karst hydrology.
3.7
Mercury in the Biota
In 1992 Lupsina et al. published a review on the total mercury and methylmercury in a species of epiphyte lichen (Hypogymnia physodes L. Nyl.) sampled in an
area which also included Idrija. The highest mercury concentration was found
near the smelting house (uS-188 ~lg/g d.w.), in comparison with the areas in the
centre of Idrija (17-48 ~lg/g) and the surrounding area (2-7 ~lg/g). The lowest
concentration was found at the control site in a mountain area (0.4 ~lg/g).
According to the findings of others workers (Bargagli et al. 1987), a good
correlation was found by the authors between mercury in the air and lichens. The
fraction of methylmercury varied from 0.06 to 3.7%.