368
T.G. Laperdina et al.
As the results of the study carried out in Zabaikalye have shown (Laperdina
et al. 1995, 1996), in water streams of the background area the most commonly
encountered concentrations of dissolved mercury range within a narrow
interval: <5-10 ng/l. However, increased background value of mercury concentrations in underground and surface waters are registered in the areas of
traditional gold mining, at sites without direct technogenic impact. Thus, the
dissolved mercury concentrations in the underground waters used for drinking
in some settlements of the Mogocha raion exceeded local background and
accounted for 50-80 ng/l. This increase may result from the long-term use of
metallic mercury during gold processing near these settlements and also from the
geological peculiarities of the areas.
Mercury contamination of surface waters with technogenic waters may cause a
dangerous deterioration in water quality, which is strongly regulated by the State
fish-breeding criteria. According to these criteria, the increase in mercury
concentrations in the areas of technogenic load must not exceed the background
level of more than 10 ng/l. The exceeding of this criterion (10-40 ng/l) was
observed in some small and medium-sized rivers (Cherny Uryum, Bugarikhta,
Khangaruk).
The elevated concentrations of dissolved mercury (10-130 ng!l) are characteristic for dredge pits and, to a lesser extent, for settling tanks. However, high
turbidity of technogenic waters determines the predominant content of
suspended mercury. Thus, for example, concentrations of dissolved and
suspended mercury accounted for 130 and 8830 ng/l, respectively, in one of the
settling tanks of the Kavykta site.
The content of suspended mercury forms in the background water streams
ranged in rather wide limits of volume «5-380 ng/l), and specific (0.4-112 mgt
kg d.w.) concentrations. The water objects, bearing technogenic load are
characterized by a wider range of suspended mercury contents: volume
concentrations from 5 to 27800 ng/l; enrichment with mercury from 0.2 to
1860 mg/kg; turbidity in the settling tanks reached up to 12070 mg/l. Positive
correlative relations were established between volume concentrations of suspended mercury and water turbidity and also between volume and specific
concentrations of mercury in suspended matter. The strength of correlation
(0.41-0.97) is different and depends on both natural and technogenic factors. As
the results of the analyses have shown, the enrichment of fine clay fractions with
mercury is by five times higher in comparison with coarse fractions, in which the
mercury content is close to Clarke values.
The maximum content of suspended mercury forms was found in the filtering
reservoir of the GDP of the Baley mine 27800 ng/l, that is higher by more than 3
orders of magnitude than the background level. In this case, suspended matter is
extremely enriched with mercury, 321 mg/kg. Such an enormous value representing a dissolved mercury concentration of 5000 ng/l, indicates very high
contamination in this reservoir. In the well located at several tens of metres from
the gold dressing plant and used for the industrial water supply, the dissolved
mercury concentration accounts for only 10 ng/l, and volume and mass
concentrations of suspended mercury for no ng/l and 22.9 mg/kg, respectively.
These values are an order of magnitude higher than similar concentrations in
T.G. Laperdina et al.
As the results of the study carried out in Zabaikalye have shown (Laperdina
et al. 1995, 1996), in water streams of the background area the most commonly
encountered concentrations of dissolved mercury range within a narrow
interval: <5-10 ng/l. However, increased background value of mercury concentrations in underground and surface waters are registered in the areas of
traditional gold mining, at sites without direct technogenic impact. Thus, the
dissolved mercury concentrations in the underground waters used for drinking
in some settlements of the Mogocha raion exceeded local background and
accounted for 50-80 ng/l. This increase may result from the long-term use of
metallic mercury during gold processing near these settlements and also from the
geological peculiarities of the areas.
Mercury contamination of surface waters with technogenic waters may cause a
dangerous deterioration in water quality, which is strongly regulated by the State
fish-breeding criteria. According to these criteria, the increase in mercury
concentrations in the areas of technogenic load must not exceed the background
level of more than 10 ng/l. The exceeding of this criterion (10-40 ng/l) was
observed in some small and medium-sized rivers (Cherny Uryum, Bugarikhta,
Khangaruk).
The elevated concentrations of dissolved mercury (10-130 ng!l) are characteristic for dredge pits and, to a lesser extent, for settling tanks. However, high
turbidity of technogenic waters determines the predominant content of
suspended mercury. Thus, for example, concentrations of dissolved and
suspended mercury accounted for 130 and 8830 ng/l, respectively, in one of the
settling tanks of the Kavykta site.
The content of suspended mercury forms in the background water streams
ranged in rather wide limits of volume «5-380 ng/l), and specific (0.4-112 mgt
kg d.w.) concentrations. The water objects, bearing technogenic load are
characterized by a wider range of suspended mercury contents: volume
concentrations from 5 to 27800 ng/l; enrichment with mercury from 0.2 to
1860 mg/kg; turbidity in the settling tanks reached up to 12070 mg/l. Positive
correlative relations were established between volume concentrations of suspended mercury and water turbidity and also between volume and specific
concentrations of mercury in suspended matter. The strength of correlation
(0.41-0.97) is different and depends on both natural and technogenic factors. As
the results of the analyses have shown, the enrichment of fine clay fractions with
mercury is by five times higher in comparison with coarse fractions, in which the
mercury content is close to Clarke values.
The maximum content of suspended mercury forms was found in the filtering
reservoir of the GDP of the Baley mine 27800 ng/l, that is higher by more than 3
orders of magnitude than the background level. In this case, suspended matter is
extremely enriched with mercury, 321 mg/kg. Such an enormous value representing a dissolved mercury concentration of 5000 ng/l, indicates very high
contamination in this reservoir. In the well located at several tens of metres from
the gold dressing plant and used for the industrial water supply, the dissolved
mercury concentration accounts for only 10 ng/l, and volume and mass
concentrations of suspended mercury for no ng/l and 22.9 mg/kg, respectively.
These values are an order of magnitude higher than similar concentrations in