Mineral Extraction: Environmental Pollution And Impacts

The extraction of mineral resources can have a range of negative impacts on the environment, including increased pollution and waste, reduced soil quality, decreased freshwater availability, and heightened seismic activity. These effects can have far-reaching consequences for both human and animal life, with potential harm to health and the disruption of habitats and ecosystems.

Mineral extraction, including mining and petroleum and gas production, can generate large amounts of pollution, from the release of toxic waste to the contamination of water sources. The Environmental Protection Agency's Toxic Releases Inventory report lists mining as the largest source of toxic waste in the United States. Acid mine drainage, caused by water coming into contact with exposed rocks containing pyrite, can lead to elevated levels of sulfuric acid and heavy metals in both surface and groundwater.

The process of extracting minerals can also destabilize soils, increase erosion, and reduce nutrient levels in terrestrial ecosystems. This, in turn, can further decrease water quality as higher levels of sediment and pollutants are carried into rivers and streams.

Additionally, groundwater extraction can cause land subsidence, and the use of hydraulic fracking to remove oil and gas has been linked to increased seismic activity in some regions.

The environmental impacts of mineral extraction vary depending on the type of mineral and the extent of its deposit, and these impacts can continue long after the deposits are no longer economically viable.

Acid mine drainage

AMD is caused by the oxidation of sulfide minerals (often pyrite, which is iron sulfide) exposed to air and water, which react to form sulfuric acid. This acid can then dissolve other harmful metals and metalloids (like arsenic) from the surrounding rock. AMD can be released anywhere on a mine site where sulfides are exposed to air and water, including waste rock piles, tailings, open pits, underground tunnels, and leach pads.

The rate and severity of AMD can be increased by certain bacteria, which accelerate the decomposition of metal ions. Colonies of these microbes, called extremophiles, occur naturally in rocks but are usually kept in low numbers by limited water and oxygen supplies. However, when a mine is abandoned and pumping ceases, water floods the mine, creating the ideal conditions for extremophiles to thrive and further lower the pH of the water.

AMD has severe impacts on fish, animals, and plants. Many impacted streams have a pH of 4 or lower, similar to battery acid. It can also cause contaminated drinking water, disrupt the growth and reproduction of aquatic plants and animals, and corrode infrastructure such as bridges.

Preventing and Treating AMD

To prevent AMD, it is essential to carefully monitor and mitigate the impacts of mineral extraction on the environment and human health. This includes ensuring that all stages of mineral extraction, processing, and use are conducted within a context of careful and transparent health surveillance and environmental monitoring.

There are also a variety of treatment options for AMD, including:

• Neutralization with calcium carbonate or lime: Raising the pH of AMD to 6-9 before discharge is permitted.
• Constructed wetlands: Natural or constructed wetlands can treat high volumes of highly acidic water.
• Precipitation of metal sulfides: Most base metals in acidic solution will precipitate in contact with free sulfide.
• Removal of toxic metals by ion exchange: Using ion-exchange resins to remove toxic metals from mine water.

Air pollution

Mineral extraction, particularly the mining of coal, oil, and natural gas, contributes to air pollution through the emission of harmful substances. Fugitive emissions from coal, oil, and natural gas extraction release volatile organic compounds (VOCs), which are a major contributor to air pollution. Additionally, the venting and flaring of gases during extraction processes result in the release of sulphur dioxide (SO2) and nitrogen oxides (NOx). These emissions have negative consequences for air quality and are known to cause acid rain.

The extraction of minerals can also lead to increased dust and particulate matter in the air, which can be harmful to nearby communities. Mining activities, such as blasting and quarrying, generate dust and fine particles that can be carried by the wind, affecting the air quality in the surrounding areas. This can be particularly detrimental to vulnerable groups within these communities, including children, the elderly, and those with pre-existing health conditions.

Furthermore, the smelting process in metal mining can release toxic metals into the air, increasing the potential for acid rain and the distribution of harmful substances over a wider area. The windblown distribution of these toxic metals poses risks not only to the immediate surroundings but also to distant regions, contributing to a more widespread decline in air quality.

In addition to the direct impacts on air quality, the extraction of mineral resources can also have indirect effects. For example, the use of fossil fuels for energy production, which is often obtained through mining processes, leads to the release of carbon dioxide (CO2) and other greenhouse gases, contributing to global climate change.

To mitigate the air pollution caused by mineral extraction, effective regulations, and monitoring systems are essential. Implementing measures to reduce emissions, improve resource efficiency, and promote sustainable practices can help minimize the negative impacts on air quality and protect the health of both local communities and the global population.

Water pollution

Water is essential to life, and a prerequisite of sustainable development is to ensure that streams, rivers, lakes, and oceans remain uncontaminated. However, human activities such as mineral extraction can seriously threaten water sources. The process of mineral extraction can consume, divert, and pollute water resources.

Types of Water Pollution from Mineral Extraction

Acid Mine Drainage

Acid Rock Drainage (ARD) is a natural process in which sulphuric acid is produced when sulphides in rocks are exposed to air and water. When large quantities of rock containing sulphide minerals are excavated from an open pit or an underground mine, it reacts with water and oxygen to create sulphuric acid. This acid is then carried off the mine site by rainwater or surface drainage and deposited into nearby streams, rivers, lakes, and groundwater. ARD can severely degrade water quality, kill aquatic life, and render water virtually unusable.

Heavy Metal Contamination & Leaching

Heavy metal pollution is caused when metals such as arsenic, cobalt, copper, cadmium, lead, silver, and zinc, which are contained in excavated rock or exposed in an underground mine, come into contact with water. Metals are leached out and carried downstream as water washes over the rock surface. Leaching is particularly accelerated in the low pH conditions created by Acid Mine Drainage.

Processing Chemicals Pollution

This type of pollution occurs when chemical agents (such as cyanide or sulphuric acid) used by mining companies to separate the target mineral from the ore spill, leak, or leach from the mine site into nearby water bodies. These chemicals can be highly toxic to humans and wildlife.

Erosion and Sedimentation

Mineral development disturbs soil and rock when constructing and maintaining roads, open pits, and waste impoundments. In the absence of adequate prevention and control strategies, the exposed earth may erode, carrying substantial amounts of sediment into streams, rivers, and lakes. Excessive sediment can clog riverbeds, smother watershed vegetation, wildlife habitats, and aquatic organisms.

Lithium Extraction

Current processes for extracting lithium are particularly water-intensive. For example, the "lithium triangle" in South America, spanning parts of Chile, Argentina, and Bolivia, contains over half of the global lithium supply, found in brine pools underneath the region's vast salt flats. Miners pump this brine into large pools on the surface of the flats, where the water evaporates, leaving behind lithium carbonate used for producing clean energy technologies. This evaporation method uses up to half a million gallons of brine water to extract one ton of lithium. Withdrawing such large quantities of brine can cause freshwater to flow into brine aquifers and mix with saltwater, resulting in the salinization of freshwater and the depletion of nearby surface and groundwater supplies.

Cobalt Extraction

Similar concerns about water use and contamination have been reported for cobalt extraction in the Democratic Republic of Congo (DRC).

Graphite Extraction

Similar concerns about water use and contamination have been reported for graphite extraction in China.

Soil erosion

The removal of vegetation during mineral extraction accelerates soil erosion. With fewer roots to anchor the soil, wind and rain can easily wash away the nutrient-rich topsoil, diminishing the land's agricultural viability and compromising the stability needed to support infrastructure. This loss of topsoil can also create challenges for establishing and maintaining vegetation cover, which is crucial for managing heat and preventing further erosion.

Additionally, the altered landscape resulting from mineral extraction can lead to increased runoff and sedimentation in nearby water bodies, negatively impacting local water resources. The natural drainage patterns of the area may be disrupted, causing localized flooding.

To mitigate the effects of soil erosion, effective rehabilitation and management strategies are essential. This includes applying organic amendments, utilizing cover crops, and implementing regenerative agricultural practices to rebuild soil nutrients and structure. Sustainable land management techniques, such as contour farming or swales, can also help retain water and manage drainage, reducing the risk of flooding and further erosion.

Overall, addressing soil erosion is crucial not only for preserving the environment but also for ensuring the long-term success and sustainability of human activities, including solar farm installations and agricultural productivity.

Greenhouse gas emissions

The combustion of fossil fuels extracted through mining activities further exacerbates greenhouse gas emissions. Fossil fuel extraction, particularly coal, oil, and natural gas, accounts for a significant portion of the environmental costs associated with the mining and resource extraction industries. The combustion of these fuels for energy production releases large amounts of carbon dioxide, contributing to global warming.

The transition to cleaner energy sources and the adoption of renewable energy technologies can help mitigate greenhouse gas emissions from the mining industry. Gold mining companies, for instance, can afford a carbon price of US$100/t CO2-e, which would impact their production costs by US$13-275/oz. This shift can be facilitated by operational efficiency, electrification, and the use of renewable energy. Additionally, the adoption of new mining technologies and energy efficiencies can play a crucial role in reducing emissions.

The mining industry has a significant role in addressing climate change and can focus on three main areas: identifying assets vulnerable to physical climate change, understanding how decarbonization will shift demand for key minerals, and implementing measures to decarbonize their operations. By taking these steps, mining companies can contribute to the global effort to limit global warming and create a more sustainable future.

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