Pollution and acid drainage

Gold can be mined through artisanal mines or day mines. Both types are based on mining methods that require the use of mercury and cyanide. Especially day mining is gradually becoming more and more widespread and lucrative.

Artisanal and open pit mines have some aspects in common. Both types of mining generate effluents containing heavy metals and chemicals, which are very often discharged into the surrounding ecosystems. Due to the increasing possibilities of open pit mining exploitations, it has now become possible to exploit sites that were originally considered as unexploitable.

Open pit mines require the use of mercury and cyanide and thus produce lots of heavy metals. In many mining methods, a cyanide or mercury solution is sprayed on rocks in order to separate gold from other ores. Since the damaging minerals are often not protected or properly discharged, this process often leads to the dumping of heavy metals, such as lead and arsenic, in groundwater. The most well-known negative result of this poisonous dumping is the creation acid drainage. This type of drainage is the process whereby heavy metals, which can originally be found in the lithosphere of the earth surface, are excavated and brought to the atmosphere, where they do not belong. In this way, they are being exposed to water and oxygen. The confrontation of different ores containing heavy metals in combination with their exposure to oxygen and rain after they have reached the earth surface creates the ideal circumstances for the formation of acid drainage. Once this drainage process has begun, it is very difficult to make it end and it can therefore continue for ages. Acid drainage is marked by a rusty brown colour and poses a serious threat to the local flora and fauna. The pollution caused by this drainage results in a deterioration of the life quality of all organisms in the environment.

Frequently occurring leaks can severely damage all living organisms that can be found in rivers, even in a short period of time.  Due to the incautious discharging, noxious substances like heavy metals, solutions and effluents full of chemical waste materials end up in the atmosphere. This inconsiderate discharging of poisonous effluents evokes a serious deterioration of the air quality. Another negative consequence is the emitting and continuous presence of dust in the atmosphere. Moreover, the trucks and heavy machines that are used for the construction of the mine and the general transport generate loads of polluting gases. The remelting of the mined gold also deteriorates the air quality and creates acid rain.

The continuous leakage of minerals and heavy metals into the earth surface results into soil degradation, which can last for ages. Moreover, several reservoirs for chemical wastewater collapse due to the high pressure of additional effluents, with all its consequences. Such outcomes can only be prevented by means of a complete coating of the rock surfaces that are damaged by the mining. Yet, such coating is very uncommon in reality. Once the mining process has started, the detrimental effects become almost fully irreversible. For instance, the British soil still contains traces of mercury, even though the mines were used by the Roman population ages ago.

Corporate engineers are responsible for the calculation of the firmness of the dams that collect the wastewater. Even so, these dams need to be adapted and heightened constantly, as new effluents are added regularly. Therefore, it becomes impossible to guarantee that the solidity and sustainability of the dam constructions is preserved. Another risk is the constant threat of earthquakes, which severely weakens the solidity of the dams.

In 2009, The San Martin mine in Honduras attracted international attention, when it was found that there were substantial soil pollutions due to the presence of heavy metals, such as cyanide and arsenic, and acid drainage. These damaging effects of soil contaminations are not limited to the environment, but also severely affect the people’s quality of life. The bodies of the local population are marked by a high dosis of toxic substances, such as mercury, arsenic and lead, which lead to respiratory, skin and digestion problems. As the mine is used 200 times as much as allowed, it becomes a real challenge for the local population to have access to potable water. As a consequence, the local population is forced to buy drinking water imported by trucks.