306
A. Gnamus and M. Horvat
relatively small number of animals was examined so far. Despite roe deer being
an abundant mammal species in the polluted Idrija region, it is relatively difficult
to obtain a large number of animal tissues from the polygons where Hg values in
environment are heavily enhanced. As roe deer population occupying territories
in the heavily polluted town's suburban area inside the Idrija valley is small, the
culling of the animals must be reasonable and proportionate to the wider
examined area, so that the normal population structure is preserved (Gnamus
et al. 1991).
Despite elemental Hg being the main Hg form introduced into the environment, and inorganic Hg compounds representing the majority of the form found
in the contaminated terrestrial environment of Idrija, large Me-Hg values and
percentages were measured in roe deer tissues compared to its concentrations in
the air, soil profiles and roe deer plant foodstuffs from the area. Large portions of
Hg were present as Me-Hg in the majority of selected roe deer tissues except
lungs, spleen, liver and kidney. Often Me-Hg concentrations in roe deer tissues
are of the same order of magnitude as in the composite vegetation samples,
despite T-Hg concentration values in the latter are being much higher (see Tables
4,5,6). Thus, average concentrations of Me-Hg in the contaminated soil profile
samples from the Idrija area account only for up to 0.04% of T -Hg (range 0.005
to 0.9%; Gnamus et al. 1996), and in vegetation samples around 0.27% of T-Hg
(range 0.14 to 2%), whereas Me-Hg concentrations in most roe deer tissues from
the contaminated area varied from 20 to 90% of T -Hg - for example in roe deer
muscle it represents up to 80% (range 22 to 80%). The means of the Me-Hg
percentage values for ten different animal tissues compared to the percentages of
Me-Hg in soil profiles, plants and human tissue samples from the Idrija area and
unpolluted areas of Slovenia are presented in Fig. 5a,b. Relatively low percentages
of Me-Hg in roe deer tissues obtained from the contaminated area were found in
blood, tissues of the internal organs like lungs, spleen, liver and kidneys, and eye
sections, where mean Me-Hg values varied from 0.08% in kidney cortex up to
15% in lungs and eye sections with the exception of Lens crystallina with the MeHg percentage between 40 and 50%. Therefore, we believe that a selective
accumulation of particular Hg species occurs in the target tissues of mercury
accumulation at the level of the primary consumers.
Due to the low percentage of Me-Hg in composite vegetation foodstuffs of roe
deer, and the high Me-Hg percentage in most of the roe deer tissues, a complex
sequence of mechanisms involving processes of selective uptake and elimination,
transformation and retention must take place in the metabolism of these
herbivorous animals. Through these processes relative elevation of roe deer
tissue Me-Hg content compared to their plant diet occurs. Most probably, the
primary reason for enhanced Me-Hg values in roe deer tissues may be selective
retention of methylated Hg species from the vegetation diet in the body tissues of
the herbivore.
Indeed, high Me-Hg values in tissues of roe deer living in the contaminated
area confirm the widely accepted feature that in animal tissues Me-Hg is
especially accumulated. It is believed that accumulation and bioconcentration
processes are expressed at different metabolic rates in each specimen, and
therefore tissue Me-Hg concentrations varied between specimens living in the
A. Gnamus and M. Horvat
relatively small number of animals was examined so far. Despite roe deer being
an abundant mammal species in the polluted Idrija region, it is relatively difficult
to obtain a large number of animal tissues from the polygons where Hg values in
environment are heavily enhanced. As roe deer population occupying territories
in the heavily polluted town's suburban area inside the Idrija valley is small, the
culling of the animals must be reasonable and proportionate to the wider
examined area, so that the normal population structure is preserved (Gnamus
et al. 1991).
Despite elemental Hg being the main Hg form introduced into the environment, and inorganic Hg compounds representing the majority of the form found
in the contaminated terrestrial environment of Idrija, large Me-Hg values and
percentages were measured in roe deer tissues compared to its concentrations in
the air, soil profiles and roe deer plant foodstuffs from the area. Large portions of
Hg were present as Me-Hg in the majority of selected roe deer tissues except
lungs, spleen, liver and kidney. Often Me-Hg concentrations in roe deer tissues
are of the same order of magnitude as in the composite vegetation samples,
despite T-Hg concentration values in the latter are being much higher (see Tables
4,5,6). Thus, average concentrations of Me-Hg in the contaminated soil profile
samples from the Idrija area account only for up to 0.04% of T -Hg (range 0.005
to 0.9%; Gnamus et al. 1996), and in vegetation samples around 0.27% of T-Hg
(range 0.14 to 2%), whereas Me-Hg concentrations in most roe deer tissues from
the contaminated area varied from 20 to 90% of T -Hg - for example in roe deer
muscle it represents up to 80% (range 22 to 80%). The means of the Me-Hg
percentage values for ten different animal tissues compared to the percentages of
Me-Hg in soil profiles, plants and human tissue samples from the Idrija area and
unpolluted areas of Slovenia are presented in Fig. 5a,b. Relatively low percentages
of Me-Hg in roe deer tissues obtained from the contaminated area were found in
blood, tissues of the internal organs like lungs, spleen, liver and kidneys, and eye
sections, where mean Me-Hg values varied from 0.08% in kidney cortex up to
15% in lungs and eye sections with the exception of Lens crystallina with the MeHg percentage between 40 and 50%. Therefore, we believe that a selective
accumulation of particular Hg species occurs in the target tissues of mercury
accumulation at the level of the primary consumers.
Due to the low percentage of Me-Hg in composite vegetation foodstuffs of roe
deer, and the high Me-Hg percentage in most of the roe deer tissues, a complex
sequence of mechanisms involving processes of selective uptake and elimination,
transformation and retention must take place in the metabolism of these
herbivorous animals. Through these processes relative elevation of roe deer
tissue Me-Hg content compared to their plant diet occurs. Most probably, the
primary reason for enhanced Me-Hg values in roe deer tissues may be selective
retention of methylated Hg species from the vegetation diet in the body tissues of
the herbivore.
Indeed, high Me-Hg values in tissues of roe deer living in the contaminated
area confirm the widely accepted feature that in animal tissues Me-Hg is
especially accumulated. It is believed that accumulation and bioconcentration
processes are expressed at different metabolic rates in each specimen, and
therefore tissue Me-Hg concentrations varied between specimens living in the