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Sources of heavy metals
Heavy metals
in air
Heavy metals in precipitation
Heavy metals in waste water
Heavy metals in fish and molluscs
Heavy metals in crops
Sources of heavy metals
The emissions of Cd, Pb, and Hg are relatively low. The sources
of heavy metal pollution are mainly combustion of fossil fuel (coal,
shale oil, heavy oil, and others) and internal combustion engines
of vehicles using leaded fuels, The imported loads of Cd, Pb and
Hg metals and their compounds (salts) to the environment have been
increasing during the past two years, which can be explained by
economic growth.
Pressure indicator
Import of heavy metals and their compounds
(tonnes)
| Name |
1999. |
2000. |
| Compounds containing mercury |
0,06 |
4,09 |
| Lead and lead compounds |
59,4 |
2139,3 |
| Cadmium compounds |
0,4 |
0,4 |
Source: Latvian Environment Agency
Heavy metals
in air
During the past 10 years, heavy metal pollution in
air has been decreasing, which may be related to modernization of
stationary pollution sources, mainly regarding boiler houses, and a
transition to environmentally friendly fuels such as wood and
natural gas.
Regular monitoring in Riga indicate the impact of
pollutant loads (including heavy metals, e.g. lead) from
production and transport on air quality in the city.
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Heavy metals in precipitation
Data collected in various regions of Latvia during
1995-2000 indicate that the mean concentrations of Cd, Pb, Cu and
Zn have tended to decrease in atmospheric deposition, and hence
also in air.
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Heavy metals in waste water
The loads of heavy metals to surface waters can be
characterized by the heavy metal levels in municipal waste waters.
Heavy metals in fish and molluscs
Monitoring of the important river basins and the Gulf of Rīga as
part of the international HELCOM monitoring commitments has
indicated relatively low levels of heavy metals in marine fish,
excepting for cadmium. The cadmium concentrations in smelt from the
Gulf of Rīga were 80-200 µg/kg, in herring up to 170 µg/kg, and
in lamprey up to 230 µg/kg. These cadmium concentrations are
already close to the allowed dietary exposure levels.
The mercury concentration in waters of Latvia is about 0.1-1.0 µg/l.
The World Health Organization considers the maximum allowed level of
mercury in fish to be 1000 µg/kg. In fish of the Gulf of Rīga, the
mean mercury concentrations are 130-560 µg/kg. The respective Hg
levels for freshwater fish are not known. The concentrations of some
heavy metals (Cu and Zn) have increased in river molluscs in recent
years.
Heavy metals in crops
The concentrations of heavy metals in grain and
potatoes are considerably lower than the maximum allowed levels
given in legislation.
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