370
T.G. Laperdina et al.
average 0.064 mg/kg, and in technogenic flux average value accounts for
0.555 mg/kg, that is 8.6 times higher than background concentrations.
In the area of the Baleyzoloto mine the maximum mercury concentration in
bottom sediments (3.24 mg/kg) was observed in fine-grained sandy ground on
the bottom of filtering reservoirs of the GEP. The elevated concentrations were
also found in bottom sediments of some open pits. Their enrichment with
mercury accounts for the average of 0.62 mg/kg, which is approximately ten
times higher than the level of mercury concentration in background water
reservoirs. Similar results were obtained for the background and industrial water
objects in the area of the Bukuka tungsten mine. Hence, mining and processing
of rocks with elevated mercury content, characteristic of ore gold deposits and
some other hydrothermal deposits, lead to an increase in mercury content,
approximately by an order of magnitude, in bottom sediments of water systems
which are not subjected to a direct mercury load.
If sluice amalgamation was not used in processing placers by the dredge
method, the mercury content in bottom sediments of open pits, as a rule, is not
high. Similar results are also registered in settling tanks at sites of hydraulic
works. Thus, in the area of the Ksenyevsky mine, the average value in bottom
sediments of technogenic reservoirs, except for a single abnormal value
(0.130 mg/kg) accounts for 0.027 mg/kg. The average mercury concentration in
bottom sediments of settling tanks at sites of hydraulic works in the TungirOlyokma raion, except for a single abnormal value (0.131 mg/kg), accounts for
0.030 mg/kg.
6
Influence of Climatic Factors on the Extent of Mercury
Contamination Due to Gold Mining in Siberia
The most complete and comprehensive estimation of the extent of mercury
contamination due to gold mining in Siberia was performed in some areas of
Zabaykalye; therefore estimation of climatic factors influence was carried out on
the basis of the results obtained from gold mining areas of Zabaykalye.
In spite of the long-term history of gold mining in Zabaikalye and previous
intensive use of mercury amalgamation for concentration of gold-bearing raw
materials, comparatively few areas of the region are characterized by a high
mercury contamination. One of the basic reasons has to do with the severe
climatic conditions of Zabaykalye, marked by an extremely continental climate
with circumzero or negative average annual temperatures, deep seasonal freezing
of soils and grounds, massive or island spreading of permafrost, the short period
of open water in natural water streams and virtually total freezing of some of
them in winter. These conditions produce an inhibiting effect on biochemical
and geochemical processes of dissolving of metallic mercury which is transported into water systems. Dredge processing of placer deposits, as a rule, is
carried out in insulated reservoirs with derevation of the basic river bed.
T.G. Laperdina et al.
average 0.064 mg/kg, and in technogenic flux average value accounts for
0.555 mg/kg, that is 8.6 times higher than background concentrations.
In the area of the Baleyzoloto mine the maximum mercury concentration in
bottom sediments (3.24 mg/kg) was observed in fine-grained sandy ground on
the bottom of filtering reservoirs of the GEP. The elevated concentrations were
also found in bottom sediments of some open pits. Their enrichment with
mercury accounts for the average of 0.62 mg/kg, which is approximately ten
times higher than the level of mercury concentration in background water
reservoirs. Similar results were obtained for the background and industrial water
objects in the area of the Bukuka tungsten mine. Hence, mining and processing
of rocks with elevated mercury content, characteristic of ore gold deposits and
some other hydrothermal deposits, lead to an increase in mercury content,
approximately by an order of magnitude, in bottom sediments of water systems
which are not subjected to a direct mercury load.
If sluice amalgamation was not used in processing placers by the dredge
method, the mercury content in bottom sediments of open pits, as a rule, is not
high. Similar results are also registered in settling tanks at sites of hydraulic
works. Thus, in the area of the Ksenyevsky mine, the average value in bottom
sediments of technogenic reservoirs, except for a single abnormal value
(0.130 mg/kg) accounts for 0.027 mg/kg. The average mercury concentration in
bottom sediments of settling tanks at sites of hydraulic works in the TungirOlyokma raion, except for a single abnormal value (0.131 mg/kg), accounts for
0.030 mg/kg.
6
Influence of Climatic Factors on the Extent of Mercury
Contamination Due to Gold Mining in Siberia
The most complete and comprehensive estimation of the extent of mercury
contamination due to gold mining in Siberia was performed in some areas of
Zabaykalye; therefore estimation of climatic factors influence was carried out on
the basis of the results obtained from gold mining areas of Zabaykalye.
In spite of the long-term history of gold mining in Zabaikalye and previous
intensive use of mercury amalgamation for concentration of gold-bearing raw
materials, comparatively few areas of the region are characterized by a high
mercury contamination. One of the basic reasons has to do with the severe
climatic conditions of Zabaykalye, marked by an extremely continental climate
with circumzero or negative average annual temperatures, deep seasonal freezing
of soils and grounds, massive or island spreading of permafrost, the short period
of open water in natural water streams and virtually total freezing of some of
them in winter. These conditions produce an inhibiting effect on biochemical
and geochemical processes of dissolving of metallic mercury which is transported into water systems. Dredge processing of placer deposits, as a rule, is
carried out in insulated reservoirs with derevation of the basic river bed.