Mercury in Terrestrial Food Webs of the Idrija Mining Area
301
spread around Idrija. Because of the high market value of mercury, in the mine's
early days ore was frequently stolen from the mine to produce the precious metal in
improvised low recovery smelter works built in the hills around Idrija.
Deviations in vegetation and animal T-Hg values related to the distance from
the source of Hg pollution are much smaller than in the soil profiles (Gnamus
et al. 1996). The same is true for Me-Hg concentrations.
In general, the concentration differences in the composite plant samples are
expected to be small due to the relatively uniform distribution of selected plant
species over the sampling areas. The sampling site particularities are even less
expressed for roe deer due to the fact that those terrestrial mammals range over
territories with different directions of exposure. Thus, biota display more
representative data and the impact of possible locally enhanced soil Hg
concentration at certain sampling sites is less expressed due to their integrating
action.
Comparison of Me-Hg concentrations in the three contamination zones of
Idrija area and controls, relating the environmental and biota sample concentration levels, show differences much smaller than those observed for T-Hg.
Following the same territorial sample grouping as for T-Hg, Me-Hg concentrations in various types of samples are within the same order of magnitude (Table
4, Fig. 4), which suggests different features of Me-Hg accumulation incomparison
to inorganic Hg forms. Average Me-Hg concentrations in vegetation of the
heavily contaminated smelter zone (I-Sm) are about lO% higher than in the
polygon covering north-eastern suburban Idrija area (I-I), which comprises the
wider smelter area (Fig. 3a), but are approx. 25-50% higher than the average
values for those samples obtained from the areas 1-2 to 1-4 clustered in Zone A
(see Fig. 4b). Similar trends were discovered in the soil profiles from the region
(Gnamus et al. 1996). Environmental and biota samples from Zone A of the Idrija
area contained higher Me-Hg concentrations than the samples from Zone B, but
the differences were less significant than in T -Hg concentrations (see Table 4).
Me-Hg concentrations in the distinctively contaminated Zone A were approx. 4
times higher for vegetation samples and about 1.5 to 4.5 times higher for the
various roe deer tissue samples, compared to the less contaminated wider Idrija
surroundings (Zone B). On comparing Me-Hg concentrations in biota samples
from the distinctively contaminated Zone A and controls, values approx. 20
times higher were found in vegetation samples, and approx. 20 to 2lO times in
most roe deer tissues from Zone A. The exceptions were pituitary glands in
which Me-Hg contents were only 3 times higher than in controls. Average Me-Hg
concentrations in the wider Idrija surroundings (Zone B) differ from the controls
by factors of approx. 5 times for vegetation samples, and approx. lO to 80 times
for various roe deer tissues, except in the pituitary gland with approx. 3 times
higher values. Average Me-Hg concentrations in the immediate vicinity of the
smelter complex (smelter zone) are about twice as high as those measured in
vegetation samples from the Idrija forestal suburbs, approx. 8 times higher than
in the wider Idrija surroundings, and approx. 40 times higher than in controls.
However, mixed roe deer diet and roe deer tissues consistently reflect the
fluctuations in Me-Hg concentrations and T-Hg levels related to the distance
from the pollution source.
301
spread around Idrija. Because of the high market value of mercury, in the mine's
early days ore was frequently stolen from the mine to produce the precious metal in
improvised low recovery smelter works built in the hills around Idrija.
Deviations in vegetation and animal T-Hg values related to the distance from
the source of Hg pollution are much smaller than in the soil profiles (Gnamus
et al. 1996). The same is true for Me-Hg concentrations.
In general, the concentration differences in the composite plant samples are
expected to be small due to the relatively uniform distribution of selected plant
species over the sampling areas. The sampling site particularities are even less
expressed for roe deer due to the fact that those terrestrial mammals range over
territories with different directions of exposure. Thus, biota display more
representative data and the impact of possible locally enhanced soil Hg
concentration at certain sampling sites is less expressed due to their integrating
action.
Comparison of Me-Hg concentrations in the three contamination zones of
Idrija area and controls, relating the environmental and biota sample concentration levels, show differences much smaller than those observed for T-Hg.
Following the same territorial sample grouping as for T-Hg, Me-Hg concentrations in various types of samples are within the same order of magnitude (Table
4, Fig. 4), which suggests different features of Me-Hg accumulation incomparison
to inorganic Hg forms. Average Me-Hg concentrations in vegetation of the
heavily contaminated smelter zone (I-Sm) are about lO% higher than in the
polygon covering north-eastern suburban Idrija area (I-I), which comprises the
wider smelter area (Fig. 3a), but are approx. 25-50% higher than the average
values for those samples obtained from the areas 1-2 to 1-4 clustered in Zone A
(see Fig. 4b). Similar trends were discovered in the soil profiles from the region
(Gnamus et al. 1996). Environmental and biota samples from Zone A of the Idrija
area contained higher Me-Hg concentrations than the samples from Zone B, but
the differences were less significant than in T -Hg concentrations (see Table 4).
Me-Hg concentrations in the distinctively contaminated Zone A were approx. 4
times higher for vegetation samples and about 1.5 to 4.5 times higher for the
various roe deer tissue samples, compared to the less contaminated wider Idrija
surroundings (Zone B). On comparing Me-Hg concentrations in biota samples
from the distinctively contaminated Zone A and controls, values approx. 20
times higher were found in vegetation samples, and approx. 20 to 2lO times in
most roe deer tissues from Zone A. The exceptions were pituitary glands in
which Me-Hg contents were only 3 times higher than in controls. Average Me-Hg
concentrations in the wider Idrija surroundings (Zone B) differ from the controls
by factors of approx. 5 times for vegetation samples, and approx. lO to 80 times
for various roe deer tissues, except in the pituitary gland with approx. 3 times
higher values. Average Me-Hg concentrations in the immediate vicinity of the
smelter complex (smelter zone) are about twice as high as those measured in
vegetation samples from the Idrija forestal suburbs, approx. 8 times higher than
in the wider Idrija surroundings, and approx. 40 times higher than in controls.
However, mixed roe deer diet and roe deer tissues consistently reflect the
fluctuations in Me-Hg concentrations and T-Hg levels related to the distance
from the pollution source.