5. Where do the world's supplies of mercury come from?
- 5.1 How does mercury reach the world market?
- 5.2 How important is mercury recycling?
- 5.3 What is mercury used for?
5.1 How does mercury reach the world market?
The natural levels of mercury in the Earth’s crust vary from
place to place, but average about 50
mg per tonne of rock.
Mercury is mined when present in
cinnabar ores, which
generally contain about 10
kg per tonne of rock.
Mercury is also present at very low levels throughout the
biosphere. Thus, mercury
absorbed by ancient plants
may account for its presence in
fossil fuels like coal, oil
Today, the world market is supplied by mercury that is:
- newly extracted from mines;
- recovered as a by-product of the mining or refining of
other metals, minerals, natural gas and old mining waste;
- recycled from spent products and waste from industrial
- held in government reserve stocks; and
- held in private stocks, such as in
chlor-alkali and other
By the year 2000, the production of mined mercury had fallen
to a third of its level in the early 1980s. Despite low demand,
low prices and the alternative sources available, mercury is
still mined in a number of countries such as Spain, China,
Kyrgyzstan and Algeria. Moreover, unrecorded small-scale mercury
mines have been reported in Asia and Latin America.
5.2 How important is mercury recycling?
Since the 1990s, about 700 to 900
tonnes of recycled mercury
have been put on the world market every year. Most of this has
come from recently closed mercury-based
Their equipment employs a lot of mercury, though it is not
consumed in the chemical process.
Over the next decade and beyond, up to 13 000
tonnes of mercury will
become available from the European Union alone. Similarly, large
stocks of mercury held by various governments have become
surplus and could be put on the market. For instance, the US
government has a large mercury stock of 4 435 tonnes and has
suspended sales since 1994 pending an evaluation of the
potential environmental and market impacts.
The reuse and recycling of mercury replaces the mining
processes, and prevents new mercury entering the market and the
environment. However, giving preference to recycled mercury
creates complications, because an excess supply may drive the
market price down. This would encourage increased use, and thus
disposal of mercury. For this reason, certain steps are being
taken to manage supply, for example in Europe.
5.3 What is mercury used for?
Mercury is a versatile material known for thousands of years.
It is the only metal that is liquid at room temperature. It is a
good electrical conductor, has a very high
density and high
surface tension, expands
and contracts uniformly when pressure and temperature change,
and it can kill micro-organisms, including
pathogenic organisms and
Elemental mercury has
- to extract gold and silver from ore (for centuries);
- to assist the manufacture of
- in manometers, which measure and control pressure;
- in thermometers;
- in electrical and electronic switches;
- in fluorescent lamps; and
- in dental amalgam
Mercury compounds have been used:
- in batteries;
- as biocides, to
control or destroy micro-organisms, e.g. in the paper
industry, in paints and on seed grain;
- as antiseptics in
- for chemical analysis;
- as catalysts, to
make the manufacture of other chemicals more efficient; and
- in pigments and dyes, detergents, and explosives
(mainly in the past).
In industrialised countries, awareness of the potential
adverse impacts of mercury
on health and the environment has led to a reduction of both the
volume and the range of uses of mercury and its compounds,
particularly during the 1980s and 1990s. Nonetheless, mercury is
still used in many ways in some other parts of the world.