Mining and Its Environmental Impact

Written By Ava Langridge

Mining is the practice of extracting geological resources from the Earth for use as raw materials. A variety of materials are mined in numerous locations worldwide, with coal, gold, iron, and sand being among the most frequently extracted resources. Humans have been mining for thousands of years, with the oldest known mine being the Ngwenya Mine on Eswatini's Bomvu Ridge. According to radiocarbon dating, this mine dates back over 40,000 years, which means that the mining has impacted the environment for thousands of years. While mining of materials has been vital for the growth of human society, technological development and the expansion of the economy, its impact on the surrounding environment and wildlife, as well as local human populations, is almost always detrimental. As mining technologies advance to make extracting low-grade ore more profitable, how big of a hole are we really digging for ourselves?

Impact On Water Pollution 

Mining’s impact on water pollution can differ significantly depending on several factors, these include: the sensitivity of the local landscape, the makeup of the minerals being extracted, the technology used, the expertise, understanding, and environmental dedication of the company, as well as the capability to monitor and enforce adherence to environmental regulations. The increasing mechanisation of mining is a significant issue, allowing for the handling of more rock and ore materials than has previously been possible. Consequently, mine waste has increased dramatically. The effect of mining on water pollution generally falls into one of the four following categories.


Acid Mine Drainage

Acid mine drainage (AKA Acid Rock Drainage/ARD) is an intensified version of a natural phenomenon where sulphuric acid is produced when sulphides in rocks are exposed to air and water. When a quarry or mining operation excavates a significant amount of rock containing sulphide minerals, a chemical reaction takes place as it interacts with oxygen and water, a significant amount of sulphuric acid is produced as a result. When the acidity of the water reaches a certain threshold, a naturally occurring bacteria - Thiobacillus ferrooxidans - thrives and accelerates the processes of acidification and oxidation.The acid then continues to extract more trace metals from the rock.This results in a harmful chain reaction where as long as the source material is exposed to air and water, sulphuric acid will be continually generated. This phenomenon can last for hundreds, even thousands of years. Rainwater and surface runoff from the mine site transports the acid away and deposits it into nearby water sources, such as groundwater, lakes, rivers, and streams. This could severely degrade the quality of the water, exterminate aquatic life, and make the water unsuitable for use.

Heavy Metal Pollution

Heavy metal pollution is caused when metals found in excavated rock, such as copper, cobalt, arsenic, lead, cadmium, zinc, and silver, are exposed to water. As water flows over the surface of these rocks, metals leach from the material and are carried downstream.

Pollution From Processing Chemicals

This type of pollution occurs when chemical agents used during mineral extraction, such as sulphuric acid or cyanide, leak, spill, or leach from a mine site into adjacent bodies of water. Such chemicals tend to be extremely toxic to both local wildlife and humans.

Erosion And Sedimentation

Local soils and rocks are often disturbed during the construction and maintenance of roads, waste impoundments, and open pits. Without proper control measures and prevention systems, exposed earth is susceptible to erosion, resulting in considerable amounts of sediment being washed into nearby water sources. Excessive sediment, when accumulated, can clog riverbeds and suffocate watershed vegetation, aquatic organisms, and wildlife habitats.


Air pollution

The mining sector accounts for approximately 4-7% of global greenhouse gas emissions. Greenhouse gases, including CO2 and methane, can be emitted both directly and indirectly during mining operations, resulting in considerable repercussions for the climate crisis. Several air pollutants, such as O3 and NOx, can influence the metabolic functions of the proximate leaves and hinder net carbon fixation by the plant canopy. They initially settle on the soil, like heavy metals, impacting root functionality and disrupting the plant’s soil resource acquisition. Decreases in resource acquisition (the production of carbohydrates through photosynthesis, the uptake of mineral nutrients, and water absorption from the soil)  will affect plant development by changing the distribution of resources to various plant components.

When air pollution stress coincides with other stressors, such as water stress, the effects on growth depend on the complex interplay of processes within the plant. The impacts of air pollution differ depending on the type and concentration of the pollutant released. Adaptation and mitigation strategies to reduce air pollution from mining typically focus on transitioning towards cleaner energy sources. Transitioning from coal and diesel to cleaner fuels, such as gasoline, or renewable energy sources, such as solar and hydropower, are all ways to reduce greenhouse gas emissions and air pollution. Air pollution can also be addressed by enhancing the efficiency of the mine and conducting a life-cycle assessment beforehand to limit its environmental impacts.


Impact On Biodiversity

Many ecosystems and habitats are negatively impacted by mining. At the local scale, its immediate effects include the direct destruction of habitats at the mining sites. On a broader level, mining activities indirectly harm regional and global biodiversity by contributing significantly to pollution and climate change. Therefore, conservation strategies must be varied and geographically inclusive, tackling both the immediate impacts at specific locations and the wider, extensive environmental consequences. The initiation of a mine signifies a major alteration of habitats, with smaller disruptions occurring beyond the extraction site, such as contamination from mine waste byproducts. Its adverse effects can also be observed long after mining operations have concluded. Apart from the destruction of habitats, the decline of biodiversity can also be the result of direct poisoning from materials extracted from the mine or indirect poisoning via food and water, both of which adversely impact animals, plants, and microorganisms. Endemic species are especially susceptible as they require very specific environmental conditions and even minor changes to their habitats can put them at risk of extinction.These unwanted modifications to habitats, including changes in pH and temperature, disrupt the communities in the nearby regions. Habitats may even suffer from non-chemical waste or a lack of terrestrial resources, like when large rocks from the mines are carelessly left in the surrounding landscape. 

Heavy metal levels are known to decrease with distance from the mine, and the impacts on biodiversity tend to follow this trend. However, the effects can vary greatly depending on the mobility and bioavailability of the pollutant. For example, the metals in sediments might change their bioavailability and, as a result, their toxicity to aquatic life. Biomagnification is a process through which the concentration of a substance, like a pollutant or pesticide, increases as it moves up the food chain, and it plays a significant role in contaminated habitats. The impact of mining on biodiversity, provided that the levels of concentration are not sufficiently high to cause immediate death to the affected organisms, is likely amplified for species at the top of the food chain due to this process. The detrimental effects of mining on biodiversity largely rely on the type of contaminant, the concentration levels in the environment, and the traits of the ecosystem itself. Some species demonstrate considerable resilience to human-induced disturbances, whereas others may completely disappear from the contaminated zone. Furthermore, time alone does not seem to facilitate the full recovery of the habitat from pollution, and whilst some remediation initiatives are in place, in many cases, they will not restore the original diversity that existed before mining activities commenced.



Solutions 

Mining conglomerates should be using every available opportunity to make their mining operations less impactful to the environment. From reusing the excessive waste from mining, to finding eco-friendly equipment, to opting for a rehabilitation program in affected areas, every opportunity should be utilized. By introducing circularity into our systems we can combat climate change: focusing on a circular economy by reducing, reusing, repairing, and recycling materials, along with transitioning to renewable energy,can significantly minimize greenhouse gas emissions and environmental impact from mining. Some mining companies like Alcoa in Australia have implemented large-scale reforestation schemes, looking to restore every local species present at a mine site before the operations started. The following methods have also proven to be very effective in reducing the environmental impact: selective mining, in-situ leaching, and underground mining. Selective mining means concentrating on removing solely the ore-containing material, disregarding the adjacent waste rock, which decreases the volume of material that must be treated and discarded. The in-situ leaching method draws minerals directly from the ore deposit in situ, thereby lessening surface disruption and decreasing the requirement for extensive excavation. Finally, at times, underground mining can be less intrusive to the surface ecosystem than open-pit mining. More countries should be taking inspiration from countries like Chile, Mauritius and South Africa, which are already leading in providing renewable power to their mining sites. 


In conclusion, with careful steps and a global effort, it is possible to minimize the mining sector’s environmental impact in the coming years. Mining corporations should be encouraged to find eco-friendly ways to mine that are less detrimental to the environment and the people who inhabit it. Ultimately, the best way to combat the environmental impacts of mining is to put an end to the excessive extraction of natural resources from the earth by introducing circularity into our systems and promoting well-being for all, people and planet.



Written by: Gianna Hector

Edited by: Ailin Bogers




References:

Ava Langridge
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