One of the most under-publicized problems facing environmental health in
the Australia is that of toxic waste emissions or acid mine drainage (AMD)
from abandoned mining sites. It threatens the quality of the surface and
ground water supply with contamination of toxic heavy metals and high
levels of acidity. More effective and creative solutions must be found to
combat this problem quickly, in order to prevent irreparable damage to the
wildlife, plant life, and water supply .
There are two points of view with regard to acid mine drainage. Some
peoplebelieve that there is no problem. These people argue that the
contamination introduced into the watersheds is minimal or even
non-existent, and the damage to the environment is minute. Other
people argue that it is difficult to contain surface and ground water
contamination and that it can easily spread outside its source area.
Contaminants come from two primary sources in hard rock mines:
Ground water builds in the tunnels of abandoned hard rock mines (such as
silver and gold mines). This water combines with sulfide minerals and
oxygen to form sulfuric acid. The acid leaches exposed metals from the
surrounding rock walls of the tunnel, dissolving and carrying the metals
into the groundwater and surface water supplies.
Tailings piles surrounding the mining site (Tailings are the waste rocks left over from the milling
process, which are usually ground into small pieces.)
Acid rain falls onto tailings piles, which results in the same
mobilization of the metals in the rock which has been conveniently ground
up, providing more surface area from which the acid may leach minerals.
Lead, copper, zinc, cadmium, aluminum, iron, manganese and selenium are
some of the most commonly found heavy metals in the runoff from mining
areas. There are also significantly high levels of acidity in these areas.
It has been found that pH levels of about 3-4 are common in mine discharge
A pH level of 3 corresponds to an increase of 10,000 times the acidity in
'neutral' water, which has a pH level of 7. Many species of water
creatures, such as frogs and salamanders are known to have reproductive
problems in waters with pH levels much below 5.5.
Risks of high acidity on the environment
Depletion of aquatic life
- Fish, salamanders, frogs, and other aquatic species will begin to
dwindle in number, as the acidity and heavy metal content of their habitat
increases. Contamination of food chain
- Heavy metals in the water will collect in the tissues of fish and other
creatures. If enough metals collect, it can be toxic to the fish or to a
creature that eats the fish. Contamination of drinking water supply
- Toxic heavy metals remain dissolved in the acidic water from the mines.
These metals can be ingested by humans through drinking water supplies,
causing severe health problems:
Lead - brain, kidney, and nervous system damage
Cadmium - high blood pressure, liver damage, cancer
Mercury - deterioration of the nervous system
Deterioration of Dry Country ecosystems
- The damage to wildlife and water systems in the drier regions of
Australia due to toxic mining drainage will impact all aspects of the
ecosystem. Arid regions have delicate and fragile balances, with very
little buffering for increased levels of acidity in the water supply.
If action is taken to change how we handle acid mining discharge, then we
can expect to see improvements in the health of people who live near the
mines, as well as the wildlife of the mountains. The effects of past
mining practices are only beginning to be felt, so action might stop them
from getting much worse. Efforts to clean up abandoned and existing mines
would result in fewer health problems for people in mining communities.
Fortunately recent mining operations regularly put in place
practices to minimise the affects acid mine drainage.