Mercury in Terrestrial Food Webs of the Idrija Mining Area
315
and FAO/WHO for food substances (see Fig. sa,b: The FAO-WHO T-Hg limit
value for foodstuffs!).
• Environmental and biological data obtained from the studied areas in the
Idrija district were compared to enable a critical evaluation of the
environmental changes in mercury concentrations 5 to 10 years after
cessation of intensive mercury production in the mid-eighties. Despite
drastic reduction from approx. soo t/year in 1986 (several tens of kg of Hg
emitted daily from the smelter chimney), to about 2S t/year in 1990 and to
almost complete closure in the past 5 years, the mercury values in the
samples analyzed do not follow such a trend. Concentrations of mercury are
higher that one would expect from production trends alone. The results of
the study reflect the tendency of Hg species to accumulate and be retained in
environmental matrices and biota, and its capability to transform into
biologically available forms in the natural environment. This process poses a
potential contamination hazard for all living organisms in the area, especially
in the immediate vicinity of the mining/smelting complex where concentration levels are the highest. These features suggest that gradual closure of the
mine and smelting plant does not instantly solve the problem of elevated Hg
concentrations in biota inhabitating the surrounding environment, a fact
which is also to be expected from the persistence of the contaminant itself.
• The study demonstrated a useful way of estimating the current degree of
mercury and methylmercury accumulation in a particular polluted terrestrial
environment through a complex ecological survey, which includes analyses
of some environmental compartments (soil profiles) and wildlife food webs.
• Exposure gradients were recorded in both animal and plant indicators, as
well as in soil profiles when approaching the source of contamination.
•
It was demonstrated that roe deer could successfully be used as indicators of
mercury contamination in terrestrial ecosystems, and their advantages and
disadvantages in relation to their actual bioindicative value were explored
and described. Considering their high abundance and wide distribution in
Europe and Eurasia, the positive correlations with the environmental Hg
pollution and preliminary data on the relationship between Hg content in
tissue and the age of the organisms, roe deer appear to fulfill all the
conditions necessary for their use as biomonitors.
• The small number of the animals examined prevents drawing general
conclusions as concern the age/sex and mercury content correlations.
Additional roe deer specimens are required to discover the possible role of
the sex of the animals in Hg accumulation trends and to extend their age
structure. They would also enable a thorough statistical evaluation of the
results to be made.
• Despite the relatively high concentrations of Hg in some roe deer tissues, no
visual macro-morphological abnormalities were discovered. To uncover
possible adverse effects of life-time exposure of animals to elevated Hg
concentrations in the Idrija area, histological and cytogenetic tests are
required. The specific tissues which accumulate the most Hg were found and
selected for future cytogenetic and histological studies. The relative
accumulation rates for total and methylmercury concentrations were
315
and FAO/WHO for food substances (see Fig. sa,b: The FAO-WHO T-Hg limit
value for foodstuffs!).
• Environmental and biological data obtained from the studied areas in the
Idrija district were compared to enable a critical evaluation of the
environmental changes in mercury concentrations 5 to 10 years after
cessation of intensive mercury production in the mid-eighties. Despite
drastic reduction from approx. soo t/year in 1986 (several tens of kg of Hg
emitted daily from the smelter chimney), to about 2S t/year in 1990 and to
almost complete closure in the past 5 years, the mercury values in the
samples analyzed do not follow such a trend. Concentrations of mercury are
higher that one would expect from production trends alone. The results of
the study reflect the tendency of Hg species to accumulate and be retained in
environmental matrices and biota, and its capability to transform into
biologically available forms in the natural environment. This process poses a
potential contamination hazard for all living organisms in the area, especially
in the immediate vicinity of the mining/smelting complex where concentration levels are the highest. These features suggest that gradual closure of the
mine and smelting plant does not instantly solve the problem of elevated Hg
concentrations in biota inhabitating the surrounding environment, a fact
which is also to be expected from the persistence of the contaminant itself.
• The study demonstrated a useful way of estimating the current degree of
mercury and methylmercury accumulation in a particular polluted terrestrial
environment through a complex ecological survey, which includes analyses
of some environmental compartments (soil profiles) and wildlife food webs.
• Exposure gradients were recorded in both animal and plant indicators, as
well as in soil profiles when approaching the source of contamination.
•
It was demonstrated that roe deer could successfully be used as indicators of
mercury contamination in terrestrial ecosystems, and their advantages and
disadvantages in relation to their actual bioindicative value were explored
and described. Considering their high abundance and wide distribution in
Europe and Eurasia, the positive correlations with the environmental Hg
pollution and preliminary data on the relationship between Hg content in
tissue and the age of the organisms, roe deer appear to fulfill all the
conditions necessary for their use as biomonitors.
• The small number of the animals examined prevents drawing general
conclusions as concern the age/sex and mercury content correlations.
Additional roe deer specimens are required to discover the possible role of
the sex of the animals in Hg accumulation trends and to extend their age
structure. They would also enable a thorough statistical evaluation of the
results to be made.
• Despite the relatively high concentrations of Hg in some roe deer tissues, no
visual macro-morphological abnormalities were discovered. To uncover
possible adverse effects of life-time exposure of animals to elevated Hg
concentrations in the Idrija area, histological and cytogenetic tests are
required. The specific tissues which accumulate the most Hg were found and
selected for future cytogenetic and histological studies. The relative
accumulation rates for total and methylmercury concentrations were