Water is considered mining’s biggest casualty of all time given the huge scale at which mining of different types are advancing in today’s world. Acid mine drainage (AMD) is one of the largest repercussions of mining on water resources. It is a risk associated with all kinds of hardrock mines for extraction of useful metals and a significant number of coal mines suffer from acid mine drainage.
What is acid mine drainage?
As the name suggests, it is the outflow of acidic water from mining areas. It is identified by appearance of brownish-yellow precipitate with a foul smell and increase in acidity of water. Target ores for metals such as gold, copper, silver etc. or coal sometimes are sulphur bound which are known as ‘metal sulphides’.
Acid mine drainage is most commonly caused by iron sulphide called “pyrite” or “fool’s gold” which is abundantly found with almost all the metal ores. These sulphides are exposed during mining, and undergo oxidation reaction in presence of air and water to form sulphuric acid that is corrosive. The acid run off further dissolves harmful metals such as copper, aluminium, manganese, mercury, lead etc. and poison the ground or surface water system.
Acid mine drainage is an irreversible process that turns undisturbed and relatively unreactive ores into volumes of hazardous waste whose containment is extremely difficult once it reaches a water body. Acid drainage can also occur in non-mining areas such as construction sites, artificially dug areas or naturally weathered rocks termed as ‘acid rock drainage’. The process of pyrite oxidation and acid formation can be further catalysed by bacteria called as ‘extremophiles’ which can thrive in extreme conditions such as acidic environment.
Environmental impacts of acid mine drainage
Acid mine drainage can occur indefinitely for hundreds of years even after the mining activities have ended and thus affects a large horizon – ecologically and economically. The mines continue to produce acidic drainage as long as the rocks are exposed or become devoid of acid producing minerals. It is one of the single biggest non-point sources of pollution.
Some Roman mining sites in Great Britain are still producing problematic acid mine drainage, 2000 years after the stoppage of mining (CNHE, 2017). Moreover, AMD can develop at any point of the mining process – underground working, open pit mine faces, waste rock dumps, tailings deposits and ore stockpiles. In India, acid mine drainage usually comes from coal mines.
Most of the living organisms thrive well in the pH of near neutral which is 7. Acid mine drainage in some of the worst cases could decrease the pH of water to as low as less than 3. Thus it degrades streams, rivers and aquatic life forms in varying degrees depending upon the severity of pH change. It limits the growth of the river ecology in addition to unsuitable use of water for human, agriculture, industrial and recreational activities.
The increase in acidity can cause loss of sodium ions from the blood of fishes, which adversely affects the gill’s function. Prolonged exposure to low pH can be lethal for plants and animals with effects such as stunted growth, lesions, low reproductive rates and deformities (Vyawahre and Rai, 2016). Acid mine drainage is also responsible for loading a huge amount of heavy metals like lead, aluminium, manganese and more into our waterways. Aluminium is toxic to many aquatic animals and limits root development in plants leading to nutrient deficiency.
In addition to increase of acidity and release of toxic metals, neutralisation of the acid water by alkaline rocks could create an additional problem. In case of decrease in acidity, the iron which was in ferrous form turns into ferric and comes out of the water as a yellowish precipitate (solid) called ‘yellowboy’. It effectively chokes the streambed, crevices and prohibits the growth of benthic (bottom dwelling) life forms.
AMD have renouncing affects on the quality of groundwater system if the mines are located in permeable soil formations. The acidic and heavy metal containing water may percolate inside the water aquifers (underground water pockets) and gets spread throughout the underground water system which ultimately reaches human consumption via bore wells.
Prevention, mitigation and treatment of acid mine drainage
Acid mine drainage does bear a significant economic cost and irreversible environmental effects. Prevention of the acid-generating processes seems to be the only way to completely wipe out the problem of acid mine drainage but, stopping of mining is not the viable solution in most cases.
However, sulphuric acid could be stopped from forming by preventing the waste rock and mine tailings to come in contact with air by strategies such as submerging the tailings under water, sealing them behind barriers or burying them underground (groundtruthseeking.org, 2010). Nonetheless, isolating and containing huge amount of the generated waste is practical either above or below ground thus storing it for a future possibility or treating them with the help of technological advancement.
In most cases it is impossible to completely treat the contaminated water from acid mine drainage due to its high cost, inefficient technology and easily diffusible quality of water. But, its consequences could be limited by treating the water before releasing it into the environment through passive and active technologies (Johnson and Hallberg, 2005).
- Passive Treatment- It is the use of naturally occurring biological and chemical reactions that could be employed to reduce the acidity of AMD. For example, ‘bioreactors’ which works on use of sulphate-reducing microbes that precipitate out dissolved harmful metals. Another method is the creation of artificial wetlands where microbes can remove the heavy metals from the mine water. Both these methods are limited to small scale mines since it is expensive and requires a huge area of land. However, operation and maintenance of passive treatment system is comparatively lesser as compared to active treatment.
- Active Treatment- It is the typical water treatment system involving the use of alkaline chemicals such as caustic soda, hydrated lime, sodium carbonate etc. to decrease the acidity of mine drainage. Limestone is one very common chemical used due to its low cost and relative abundant availability. On the other hand, continued active treatment due to precipitation increases the rate of total dissolved solid (TDS) which is an important water quality parameter. Moreover, active treatment technologies are expensive due to chemical usage, equipments and huge manpower.
Receive Daily Updates
Recent Posts
- Lowering Emissions by Accelerating Forest Finance (LEAF) Coalition, a collective of the United States, United Kingdom and Norway governments, came up with a $1 billion fund.
- LEAF is supported by transnational corporations (TNCs) like Unilever plc, Amazon.com, Inc, Nestle, Airbnb, Inc as well as Emergent, a US-based non-profit.
- The world lost more than 10 million hectares of primary tropical forest cover last year, an area roughly the size of Switzerland.
- Ending tropical and subtropical forest loss by 2030 is a crucial part of meeting global climate, biodiversity and sustainable development goals. Protecting tropical forests offers one of the biggest opportunities for climate action in the coming decade.
- Tropical forests are massive carbon sinks and by investing in their protection, public and private players are likely to stock up on their carbon credits.
- The LEAF coalition initiative is a step towards concretising the aims and objectives of the Reducing Emissions from Deforestation and Forest Degradation (REDD+) mechanism.
- REDD+ was created by the United Nations Framework Convention on Climate Change (UNFCCC). It monetised the value of carbon locked up in the tropical forests of most developing countries, thereby propelling these countries to help mitigate climate change.
- It is a unique initiative as it seeks to help developing countries in battling the double-edged sword of development versus ecological commitment.
- The initiative comes at a crucial time. The tropics have lost close to 12.2 million hectares (mha) of tree cover last year according to global estimates released by Global Forest Watch.
- Of this, a loss of 4.2 mha occurred within humid tropical primary forests alone. It should come as no surprise that most of these lost forests were located in the developing countries of Latin America, Africa and South Asia.
- Brazil has fared dismally on the parameter of ‘annual primary forest loss’ among all countries. It has lost 1.7 mha of primary forests that are rich storehouse of carbon. India’s estimated loss in 2020 stands at 20.8 kilo hectares.
- Between 2002-2020, Brazil’s total area of humid primary forest reduced by 7.7 per cent while India’s reduced by 3.4 per cent.
- Although the loss in India is not as drastic as in Brazil, its position is nevertheless precarious. For India, this loss is equivalent to 951 metric tonnes worth carbon dioxide emissions released in the atmosphere.
- It is important to draw comparisons between Brazil and India as both countries have adopted a rather lackadaisical attitude towards deforestation-induced climate change. The Brazilian government hardly did anything to control the massive fires that gutted the Amazon rainforest in 2019.
- It is mostly around May that forest fires peak in India. However, this year India, witnessed massive forest fires in early March in states like Odisha, Uttarakhand, Madhya Pradesh and Mizoram among others.
- The European Union’s Copernicus Atmospheric Monitoring Service claimed that 0.2 metric tonnes of carbon was emitted in the Uttarakhand forest fires.
- Implementation of the LEAF Coalition plan will help pump in fresh rigour among developing countries like India, that are reluctant to recognise the contributions of their forest dwelling populations in mitigating climate change.
- With the deadline for proposal submission fast approaching, India needs to act swiftly on a revised strategy.
- Although India has pledged to carry out its REDD+ commitments, it is impossible to do so without seeking knowledge from its forest dwelling population.
Context:-
At the recently concluded Leaders’ Summit on Climate in April 2021, Lowering Emissions by Accelerating Forest Finance (LEAF) Coalition, a collective of the United States, United Kingdom and Norway governments, came up with a $1 billion fund plan that shall be offered to countries committed to arrest the decline of their tropical forests by 2030.
[wptelegram-join-channel link=”https://t.me/s/upsctree” text=”Join @upsctree on Telegram”]What is LEAF Coalition?
Why LEAF Coalition?
Brazil & India
According to the UN-REDD programme, after the energy sector, deforestation accounts for massive carbon emissions — close to 11 per cent — in the atmosphere. Rapid urbanisation and commercialisation of forest produce are the main causes behind rampant deforestation across tropical forests.
Tribes, Forests and Government
Disregarding climate change as a valid excuse for the fires, Indian government officials were quick to lay the blame for deforestation on activities of forest dwellers and even labelled them “mischievous elements” and “unwanted elements”.
Policy makers around the world have emphasised the role of indigenous tribes and local communities in checking deforestation. These communities depend on forests for their survival as well as livelihood. Hence, they understand the need to protect forests. However, by posing legitimate environmental concerns as obstacles to real development, governments of developing countries swiftly avoid protection of forests and rights of forest dwellers.
For instance, the Government of India has not been forthcoming in recognising the socio-economic, civil, political or even cultural rights of forest dwellers. According to data from the Union Ministry of Tribal Affairs in December, 2020 over 55 per cent of this population has still not been granted either individual or community ownership of their lands.
To make matters worse, the government has undertaken systematic and sustained measures to render the landmark Scheduled Tribes and Other Traditional Forest Dwellers (Recognition of Forest Rights) Act, 2006 ineffective in its implementation. The Act had sought to legitimise claims of forest dwellers on occupied forest land.
Various government decisions have seriously undermined the position of indigenous people within India. These include proposing amendments to the obsolete Indian Forest Act, 1927 that give forest officials the power to take away forest dwellers’ rights and to even use firearms with impunity.
There is also the Supreme Court’s order of February, 2019 directing state governments to evict illegal encroachers of forest land or millions of forest dwellers inhabiting forests since generations as a measure to conserve wildlife. Finally, there is the lack of data on novel coronavirus disease (COVID-19) deaths among the forest dwelling population;
Tardy administration, insufficient supervision, apathetic attitude and a lack of political intent defeat the cause of forest dwelling populations in India, thereby directly affecting efforts at arresting deforestation.
Way Forward
Tuntiak Katan, a global indigenous leader from Ecuador and general coordinator of the Global Alliance of Territorial Communities, aptly indicated the next steps at the Climate Summit:
“The first step is recognition of land rights. The second step is the recognition of the contributions of local communities and indigenous communities, meaning the contributions of indigenous peoples.We also need recognition of traditional knowledge practices in order to fight climate change”
Perhaps India can begin by taking the first step.