Environmental effects of mining

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Environmental effects of mining can occur at local, regional, and global scales through direct and indirect mining practices. Mining can cause erosion, sinkholes, loss of biodiversity, or the contamination of soil, groundwater, and surface water by chemicals emitted from mining processes. These processes also affect the atmosphere through carbon emissions which contributes to climate change.^[1] Some mining methods (lithium mining, phosphate mining, coal mining, mountaintop removal mining, and sand mining) may have such significant environmental and public health effects that mining companies in some countries are required to follow strict environmental and rehabilitation codes to ensure that the mined area returns to its original state. Mining can provide various advantages to societies, yet it can also spark conflicts, particularly regarding land use both above and below the surface.^[2]

Mining operations remain rigorous and intrusive, often resulting in significant environmental impacts on local ecosystems and broader implications for planetary environmental health.^[3] To accommodate mines and associated infrastructure, land is cleared extensively, consuming significant energy and water resources, emitting air pollutants, and producing hazardous waste.^[4]

According to The World Counts page "The amount of resources mined from Earth is up from 39.3 billion tons in 2002. A 55 percent increase in less than 20 years. This puts Earth’s natural resources under heavy pressure. We are already extracting 75 percent more than Earth can sustain in the long run."^[5]

Erosion

Erosion of exposed hillsides, mine dumps, tailings dams and resultant siltation of drainages, creeks and rivers can significantly affect the surrounding areas, a prime example being the giant Ok Tedi Mine in Papua New Guinea.^[6] Soil erosion can decrease the water availability for plant growth, resulting in a population decline in the plant ecosystem.^[7]

Soil erosion occurs from physical disturbances caused by mining activities (e.g. excavation, blasting, etc.) in wilderness areas. This causes disturbances of tree root systems, a crucial component in stabilizing soil and preventing erosion.^[8] Eroded materials can be transported by runoff into nearby surface water, leading to a process known as sedimentation. Moreover, altered drainage patterns redirect water flow, intensifying erosion and sedimentation of nearby water bodies.^[9] The cumulative impact results in degraded water quality, loss of habitat, and long-lasting ecological damage.

Sinkholes

A sinkhole at or near a mine site is typically caused from the failure of a mine roof from the extraction of resources, weak overburden or geological discontinuities.^[10] The overburden at the mine site can develop cavities in the subsoil or rock, which can infill with sand and soil from the overlying strata. These cavities in the overburden have the potential to eventually cave in, forming a sinkhole at the surface. The sudden failure of earth creates a large depression at the surface without warning, this can be seriously hazardous to life and property.^[11] Sinkholes at a mine site can be mitigated with the proper design of infrastructure such as mining supports and better construction of walls to create a barrier around an area prone to sinkholes. Back-filling and grouting can be done to stabilize abandoned underground workings.

Water pollution

Mining can have harmful effects on surrounding surface and groundwater.

In well-regulated mines, hydrologists[16] and geologists^[17] take careful measurements of water to take precaution to exclude any type of water contamination that could be caused by the mine's operations. The minimization of environmental degradation is enforced in American mining practices by federal and state law, by restricting operators to meet standards for the protection of surface and groundwater from contamination.^[18] This is best done through the use of non-toxic extraction processes as bioleaching.^[19] Furthermore, protection from water contamination should continue after a mine has been decommissioned, as surroundings water systems can still become contaminated years after active use. ^[20]

Air pollution

The mining industry contributes between 4 and 7% of global greenhouse gas emissions.^[21].The production of greenhouse gases, such as CO₂ and CH₄, can occur both directly and indirectly throughout the mining process and can have significant impacts on global climate change. ^[22]

Adaptation and mitigation techniques to reduce air pollution created by mining are often focused on using cleaner energy sources. [25] Switching from coal and diesel to gasoline can reduce the concentration of greenhouse gases. Furthermore, switching to renewable energy sources, such as solar power and hydropower, may reduce greenhouse gas emissions further. Air pollution may also be reduced by maximizing the efficiency of the mine and conducting a life-cycle assessment to minimize the environmental impacts. ^[26]

Acid rock drainage

Sub-surface mining often progresses below the water table, so water must be constantly pumped out of the mine in order to prevent flooding. When a mine is abandoned, the pumping ceases, and water floods the mine. This introduction of water is the initial step in most acid rock drainage situations.

estuarine conditions after the last major sea level rise, and constitutes a similar environmental hazard.^[27]

sulfide minerals (e.g. Pyrite) are exposed to water and air, producing an acidic, sulfate-rich drainage.^[28] These acidic waters can leach out various heavy metals from the surrounding rocks and soil. The acidic and metal-rich AMD is a major source of environmental pollution, contaminating nearby surface waters and groundwater, harming ecosystems and rendering water unsuitable for drinking.^[29] AMD can persist for extended periods, even long after mining activities have ceased, leading to continual environmental degradation.^[30]

The five principal technologies used to monitor and control water flow at mine sites are diversion systems, containment ponds, groundwater pumping systems, subsurface drainage systems, and subsurface barriers. In the case of AMD, contaminated water is generally pumped to a treatment facility that neutralizes the contaminants.[31] A 2006 review of environmental impact statements found that "water quality predictions made after considering the effects of mitigation largely underestimated actual impacts to groundwater, seeps, and surface water".^[32]

Heavy metals

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least 5 times greater than that of water. Heavy metals are not readily degradable and therefore, are subjected to persistence in the environment and bioaccumulation in organisms.^[33] Their multiple industrial, domestic, agricultural, medical and technological applications have led to their wide distribution in the environment; raising concerns over their potential effects on human health and the environment.^[34]

Naturally occurring heavy metals are displayed in shapes that are not promptly accessible for uptake by plants. They are ordinarily displayed in insoluble shapes, like in mineral structures, or in precipitated or complex shapes that are not promptly accessible for plant take-up. Normally happening heavy metals have a high adsorption capacity in soil and are hence not promptly accessible for living organisms. However, the impacts of heavy metal transformation and interactions with soil organisms is highly dependent on the physicochemical properties of the soil and the organisms present.^[35] The holding vitality between normally happening heavy metals and soil is exceptionally high compared to that with anthropogenic sources.^[36]

Dissolution and transport of metals and

Superfund site, also suffers from heavy metal contamination. Water in the mine containing dissolved heavy metals such as lead and cadmium leaked into local groundwater, contaminating it.^[37] Furthermore, the presence of heavy metals in freshwater may also affect the water chemistry. High concentrations of heavy metals can impact pH, buffering capacity, and dissolved oxygen.^[38] Long-term storage of tailings and dust can lead to additional problems, as they can be easily blown off site by wind, as occurred at Skouriotissa, an abandoned copper mine in Cyprus. Environmental changes such as global warming and increased mining activity may increase the content of heavy metals in the stream sediments.^[39] These impacts may also be enhanced in areas located downstream from the heavy metal source.^[40]

Effect on biodiversity

Mining impacts biodiversity across various spatial dimensions. Locally, the immediate effects are seen through direct habitat destruction at the mining sites. On a broader scale, mining activities contribute to significant environmental problems such as pollution and climate change, which have regional and global repercussions. Consequently, conservation strategies need to be multifaceted and geographically inclusive, tackling both the direct impacts at specific sites and the more extensive, far-reaching environmental consequences.^[41] The implantation of a mine is a major habitat modification, and smaller perturbations occur on a larger scale than exploitation site, mine-waste residuals contamination of the environment for example. Adverse effects can be observed long after the end of the mine activity.^[42] Destruction or drastic modification of the original site and anthropogenic substances release can have major impact on biodiversity in the area.^[43] Destruction of the habitat is the main component of biodiversity losses, but direct poisoning caused by mine-extracted material, and indirect poisoning through food and water, can also affect animals, vegetation and microorganisms. Habitat modification such as pH and temperature modification disturb communities in the surrounding area. Endemic species are especially sensitive, since they require very specific environmental conditions. Destruction or slight modification of their habitat put them at the risk of extinction. Habitats can be damaged when there is not enough terrestrial product as well as by non-chemical products, such as large rocks from the mines that are discarded in the surrounding landscape with no concern for impacts on natural habitat.^[44]

Concentrations of

sediments could modify their bioavailability, and thus their toxicity for aquatic organisms.^[45]

Biomagnification plays an important role in polluted habitats: mining impacts on biodiversity, assuming that concentration levels are not high enough to directly kill exposed organisms, should be greater to the species on top of the food chain because of this phenomenon.^[46]

Adverse mining effects on biodiversity depend a great extent on the nature of the contaminant, the level of concentration at which it can be found in the environment, and the nature of the

mining activity

took place.

Aquatic organisms

The mining industry can impact aquatic biodiversity through different ways. One way can be direct poisoning;

Osisko lake

in Rouyn-Noranda

Factors that impact communities in

One big case study that was considered extremely toxic to aquatic organisms was the contamination that occurred in Minamata Bay.^[54] Methylmercury was released into wastewater by industrial chemical company's and a disease called Minamata disease was discovered in Kumamoto, Japan.^[54] This resulted in mercury poisoning in fishes and shellfishes and it was contaminating surrounding species and many died from it and it impacted anyone that ate the contaminated fishes.^[54] Another significant case study illuminates the impact of phosphate mining on coral reef development adjacent to Christmas Island.^[55] In this scenario, phosphate-rich runoff was transported from local waterways to coral reefs off the coast, where reef sediment phosphate levels reached some of the highest levels ever recorded in Australian reefs at 54,000 mg/kg.^[55] Phosphate contamination has resulted in a noticeable decline in keystone reef-building species, such as crustose coralline algae and branching coral.^[55] This decline is likely due to phosphorus serving as a fertilizer for macro algae, allowing them to outcompete calcareous organisms.^[55]

Microorganisms

When assessing the potential risks of mining to marine microbiomes, it is important to broaden the scope to include other vulnerable communities, such as those found at the seafloor, which are at risk of ecosystem degradation due to deep-sea mining.^[59] Microbial life plays a vital role in fulfilling a variety of niches and supporting the productivity of biogeochemical cycles within seafloor ecosystems.^[59] Primary zones of deep-sea mining include operational hydrothermal vents along spreading centers (e.g., mid-ocean ridges, volcanic arcs) on the ocean floor where sulfide minerals were deposited.^[59] Other extraction zones include inactive hydrothermal vents with similar mineral deposits, polymetallic protuberances (mainly manganese) along the ocean floor, and sometimes polymetallic crusts (cobalt crusts) left behind at seamounts.^[59] These mineral deposits are often found in exotic ecosystems capable of surviving under extreme chemical conditions and abnormally high temperatures.^[59] Resource extraction has only increased over time, leading to the potential for significant losses of microbial ecosystem services at hydrothermal vents and increased ecosystem service degradation at inactive massive sulfide deposits.^[60] Potential drivers of ecosystem degradation via deepsea mining include acidification, the release of toxic heavy metals, removal of slow-growing benthic fauna, burial and respiration impairment of benthic organisms from the generation of sediment plumes, and disruption of the food supply chain among benthopelagic species.^[60] These potential outcomes can alter the chemical balance of these environments, leading to a cascade of declines in benthic and pelagic species that rely on hydrothermal vents as sources of nutrient availability.^[60] Ensuring the preservation of hydrothermal microbes and the species that depend on them is critical for retaining the rich biodiversity of seafloor environments and the ecosystem services they provide^[59]

Macro-organisms

Water

Plants can be affected through direct poisoning, for example arsenic soil content reduces bryophyte diversity.^[49] Vegetation can also be contaminated from other metals as well such as nickel and copper. ^[66] Soil acidification through pH diminution by chemical contamination can also lead to a diminished species number.^[49] Contaminants can modify or disturb microorganisms, thus modifying nutrient availability, causing a loss of vegetation in the area.^[49] Some tree roots divert away from deeper soil layers in order to avoid the contaminated zone, therefore lacking anchorage within the deep soil layers, resulting in the potential uprooting by the wind when their height and shoot weight increase.^[64] In general, root exploration is reduced in contaminated areas compared to non-polluted ones.^[48] Plant species diversity will remain lower in reclaimed habitats than in undisturbed areas.^[48] Depending on what specific type of mining is done, all vegetation can be initially removed from the area before the actual mining is started. ^[67]

Cultivated crops might be a problem near mines. Most crops can grow on weakly contaminated sites, but yield is generally lower than it would have been in regular growing conditions. Plants also tend to accumulate heavy metals in their aerial organs, possibly leading to human intake through fruits and vegetables.^[68] Regular consumption of contaminated crops might lead to health problems caused by long-term metal exposure.^[42] Cigarettes made from tobacco growing on contaminated sites might also possibly have adverse effects on human population, as tobacco tends to accumulate cadmium and zinc in its leaves.^[69]

Moreover, plants which have a high tendency to accumulate heavy metals, such as Noccaea caerulescens, may be used for phytoextraction ^[70][71] In the phytoextraction process, plants will extract heavy metals present in the soil, and store them in portions of the plant which can be easily harvested. Once the plant which has accumulated the heavy metals is harvested, the stored heavy metals are effectively removed from the soil. ^[72]

Animals

Habitat destruction is one of the main issues of mining activity. Huge areas of natural habitat are destroyed during mine construction and exploitation, forcing animals to leave the site.^[73] In addition, desirable minerals exist across all biodiversity-rich areas, and future mineral demands are expected to rise.^[74] This indicates a significant risk for animal biodiversity, considering mining is believed to have some of the most profound negative impacts on local fauna, such as reducing the availability of food and shelter, which in turn limits the number of individuals a region can sustain.^[75] Moreover, mineral exploitation poses additional threats to wildlife beyond habitat degradation, mining is believed to produce adverse impacts on wildlife in forms such as soil and water contamination, suppression of vegetation, and modifications in landscape structure.^[76]

Landscape alterations, in particular, pose a significant threat to medium and large-sized forest-dependent mammals that require large areas to meet their needs.

Microorganisms are extremely sensitive to environmental modification, such as modified pH,[49] temperature changes or chemical concentrations due to their size. For example, the presence of arsenic and antimony in soils have led to diminution in total soil bacteria.^[49] Much like waters sensitivity, a small change in the soil pH can provoke the remobilization of contaminants,^[77] in addition to the direct impact on pH-sensitive organisms.

Microorganisms have a wide variety of genes among their total population, so there is a greater chance of survival of the species due to the resistance or tolerance genes in that some colonies possess,^[78] as long as modifications are not too extreme. Nevertheless, survival in these conditions will imply a big loss of gene diversity, resulting in a reduced potential for adaptations to subsequent changes. Undeveloped soil in heavy metal contaminated areas could be a sign of reduced activity by soils microfauna and microflora, indicating a reduced number of individuals or diminished activity.^[49] Twenty years after disturbance, even in rehabilitation area, microbial biomass is still greatly reduced compared to undisturbed habitat.^[48]

Arbuscular mycorrhiza fungi are especially sensitive to the presence of chemicals, and the soil is sometimes so disturbed that they are no longer able to associate with root plants. However, some fungi possess contaminant accumulation capacity and soil cleaning ability by changing the biodisponibility of pollutants,^[64] this can protect plants from potential damages that could be caused by chemicals.^[64] Their presence in contaminated sites could prevent loss of biodiversity due to mine-waste contamination,^[64] or allow for bioremediation, the removal of undesired chemicals from contaminated soils. On the contrary, some microbes can deteriorate the environment: which can lead to elevated SO4 in the water and can also increase microbial production of hydrogen sulfide, a toxin for many aquatic plants and organisms.^[64]

Waste materials

Tailings

Mining processes produce an excess of waste materials known as tailings. The materials that are left over after are a result of separating the valuable fraction from the uneconomic fraction of ore. These large amounts of waste are a mixture of water, sand, clay, and residual bitumen. Tailings are commonly stored in tailings ponds made from naturally existing valleys or large engineered dams and dyke systems.^[79] Tailings ponds can remain part of an active mine operation for 30–40 years. This allows for tailings deposits to settle, or for storage and water recycling.^[79]

Tailings have great potential to damage the environment by releasing toxic metals by acid mine drainage or by damaging aquatic wildlife;^[80] these both require constant monitoring and treatment of water passing through the dam. However, the greatest danger of tailings ponds is dam failure. Tailings ponds are typically formed by locally derived fills (soil, coarse waste, or overburden from mining operations and tailings) and the dam walls are often built up on to sustain greater amounts of tailings.^[81] The lack of regulation for design criteria of the tailings ponds are what put the environment at risk for flooding from the tailings ponds.

Some heavy metals that accumulate in tailings, such as thorium, are linked to increase cancer risk.^[82] The tailings around China's Bayan Obo mine contains 70 000 tons of thorium.^[83][84] Contaminated groundwater is moving towards the Yellow River due to the absence of an impermeable lining for the tailing dam.^[83][85]

Spoil tip

A spoil tip is a pile of accumulated overburden that was removed from a mine site during the extraction of coal or ore. These waste materials are composed of ordinary soil and rocks, with the potential to be contaminated with chemical waste . Spoil is much different from tailings, as it is processed material that remains after the valuable components have been extracted from ore.^[86] Spoil tip combustion can happen fairly commonly as, older spoil tips tend to be loose and tip over the edge of a pile. As spoil is mainly composed of carbonaceous material that is highly combustible, it can be accidentally ignited by the lighting fire or the tipping of hot ashes.^[87] Spoil tips can often catch fire and be left burning underground or within the spoil piles for many years.

Effects of mine pollution on humans

The long-term effects associated with air pollution are plenty including chronic asthma, pulmonary insufficiency, and cardiovascular mortality. According to a Swedish cohort study, diabetes seems to be induced after long-term air pollution exposure. Furthermore, air pollution seems to have various malign health effects in early human life, such as respiratory, cardiovascular, mental, and perinatal disorders, leading to infant mortality or chronic disease in adult age. Discuss contamination basically influences those living in huge urban zones, where street outflows contribute the foremost to the degradation of discuss quality. There's moreover a threat of mechanical mishaps, where the spread of a harmful haze can be lethal to the populaces of the encompassing regions. The scattering of poisons is decided by numerous parameters, most outstandingly barometrical soundness and wind.[91]

Deforestation

With

Lithium does not occur as the metal naturally since it is highly reactive, but is found combined in small amounts in rocks, soils, and bodies of water.^[98] The extraction of lithium in rock form can be exposed to air, water, and soil.^[99] Furthermore, batteries are globally demanded for containing lithium in regards to manufacturing, the toxic chemicals that lithium produce can negatively impact humans, soils, and marine species.^[98] Lithium production increased by 25% between 2000 and 2007 for the use of batteries, and the major sources of lithium are found in brine lake deposits.^[100] Lithium is discovered and extracted from 150 minerals, clays, numerous brines, and sea water, and although lithium extraction from rock-form is twice as expensive from that of lithium extracted from brines, the average brine deposit is greater than in comparison to an average lithium hard rock deposit.^[101]

Phosphate mining

Phosphate-bearing rocks are mined to produce phosphorus, an essential element used in industry and agriculture.^[102] The process of extraction includes removal of surface vegetation, thereby exposing phosphorus rocks to the terrestrial ecosystem, damaging the land area with exposed phosphorus, resulting in ground erosion.^[102] The products released from phosphate ore mining are wastes, and tailings, resulting in human exposure to particulate matter from contaminated tailings via inhalation and the toxic elements that impact human health are (Cd, Cr, Zn, Cu and Pb).^[103]

Oil shale mining

Mountaintop removal mining (MTR) occurs when trees are cut down, and coal seams are removed by machines and explosives.^[106] As a result the landscape is more susceptible to flash flooding and causing potential pollution from the chemicals.^[107] The critical zone disturbed by mountaintop removal causes degraded stream water quality towards the marine and terrestrial ecosystems and thus mountaintop removal mining affect hydrologic response and long-term watersheds.^[108]

Sand mining

Sand mining and gravel mining creates large pits and fissures in the earth's surface. At times, mining can extend so deeply that it affects ground water, springs, underground wells, and the water table.^[109] The major threats of sand mining activities include channel bed degradation, river formation and erosion.^[110] Sand mining has resulted in an increase of water turbidity in the majority offshore of Lake Hongze, the fourth largest freshwater lake located in China.^[111]

Mitigation

Various mitigation techniques exist to reduce the impacts of mining on the environment; however, the technique deployed is often dependent on the type of environment and severity of the impact. ^[112] To ensure completion of reclamation, or restoring mine land for future use, many governments and regulatory authorities around the world require that mining companies post a bond to be held in escrow until productivity of reclaimed land has been convincingly demonstrated, although if cleanup procedures are more expensive than the size of the bond, the bond may simply be abandoned. Furthermore, effective mitigation is highly dependent on government policy, economic resources, and the implementation of new technology. ^[113] Since 1978 the mining industry has reclaimed more than 2 million acres (8,000 km²) of land in the United States alone. This reclaimed land has renewed vegetation and wildlife in previous mining lands and can even be used for farming and ranching.

Specific sites

• Tui mine in New Zealand
• Stockton mine
  in New Zealand
• Northland Pyrite Mine in Temagami, Ontario, Canada
• Sherman Mine in Temagami, Ontario, Canada
• Ok Tedi Mine in Western Province, Papua New Guinea
• The Berkeley Pit
• Wheal Jane Mines

See also

• Environmental impact of deep sea mining
• Environmental effects of placer mining
• Environmental impact of gold mining
• Environmental impact of zinc mining
• List of environmental issues
• Appalachian Voices, a lobby group in the United States
• Mining
• Natural resource

References