Metals ions from a group of mines called the Consolidation Mine are being leached from mine tailings into bodies of water through a process known as acid mine drainage (AMD). Our project is targeted at this large issue in our local area. To fully understand the issue, it is necessary to obtain a strong understanding of it through literature research. We have looked into the issue in our local area in detail, whilst also studying how the issue is present around the world, and how these issues affect the health of the local flora and fauna. Some of the mines that make up the Consolidated mines are the following:
- Wheal Jane
- Wheal Maid
- Wheal Girl
- Wheal Virgin
- Wheal Fortune
- Carharrack mine
A variety of metals have been mined at these sites, including: arsenic, copper, silver, zinc, tin and lead. (Anon., 2017). Basing our project on a local issue has allowed us to collect first-hand data from one of these sites, Wheal Maid, which we have used directly to influence our project. This was particularly important for us as we wanted to make sure that we had up to date data on the metal concentrations which is something that can’t always be attained from literature. This allowed us to understand which metals ions were causing the contamination of the water and how high these concentrations are so that we can consider the effectiveness of our system at extracting metals on this scale.
The Wheal Maid site consists of two tailing lagoons that are contaminated with a variety of metals (Carrick District Council, 2008).The water bodies at this site are being contaminated by leaching of variety of metals, including arsenic, cadmium, copper, chromium, iron, lead, nickel and zinc, from the soil into the lagoons. The recent rise in temperature around the time we visited the site meant that the lagoons were much smaller in volume than we expected. See below a comparison to how the site usually looks.
Whilst the Wheal Maid site has been fenced off and deemed too hazardous for humans (Watson, 2012) the area is still regularly used by walkers, mountain bikers and motorcyclists. (Ivall, 2007). This highlights the need to clean up the water as an active approach in comparison to just deterring visitors from the site.
This is also a wider problem. On a global scale, water is being polluted by toxic metals that our project could be used to tackle. With the current treatment methods, in the UK, the cost of cleaning water polluted with metal ions could be around £400 million over the next 10 years. This has highlighted that there is a real need for an effective low-cost solution that doesn’t cause further disruption to the natural environment (Watson, 2012).
History of the Consolidation Mine and Wheal Maid
The Consolidation Mine, also known as the Consols, forms part of the Cornwall and West Devon Mining Landscape World Heritage Site. The Mine used to be several smaller mines until underground workings of these mines were amalgamated in 1782. The Consols was a massively successful copper mine. Such was its fame that many other mines were opened using the same name, with the hope to profit by association.
Wheal Maid is one of the Consols sites with one of the largest sources of pollution in the area. It is an abandoned site that is owned by the Gwennap Parish Council, having been purchased for £1 from Carnon Enterprises (Carrick District Council, 2008). Wheal Maid was mined while the Consols were in operation until the 1870s, and then became a site for taking fine-grained mineral processing waste (tailings) from the mill facilities at the former Mount Wellington tin mine during the 1970s and 80s. The waste was taken to a valley infill at Wheal Maid consisting of two lagoons separated by three dams and contains approximately 220,000m3 of tailings. More recently, In response to local pressure, the Carrick District Council asked the Environmental Agency to conduct an environmental quality inspection which took place in 2007 (Carrick District Council, 2008).
The investigation concluded that Wheal Maid is a contaminated site, due to the levels of arsenic in the soil. The investigation stated that there is a significant possibility of significant harm to young children using the site for BMX/mountain biking from exposure to arsenic through the inhalation, ingestion and dermal absorption pathways from the soil. The controlled waters risk assessment showed that the site is causing pollution of controlled waters by leaching of arsenic, cadmium, copper, chromium, iron, lead, nickel and zinc through the toe of the lower lagoon into the St. Day Stream. It was further concluded that the pollution of controlled waters is likely to be caused by leaching of the above pollutants into groundwater beneath the site and through the culvert wall into the St. Day Stream (Carrick District Council, 2008).
Wheal Jane, part of the Consoles, was a seriously worked tin mine. When Wheal Jane was an operational, mine water levels and water quality were monitored and maintained by the pumping of partially treated water into the Carnon River. This work was overseen by the Environment Agency. However in 1991 a government grant that allowed for the dewatering of the mines was withdrawn and Wheal Jane was closed. Further monitoring of the mine water showed that water with a high acidity was discharging into Carnon River via an passage. To prevent this, the water already discharged was lime dosed (to increase the pH) , the passage was plugged and the remaining water pumped into the Wheal Jane tailing Dam. (Anon., n.d.). In early 1992, due to technical problem, pumping of the passage was suspended. Whilst alternative solutions were being considered the tunnel burst releasing 45 million litres of acidic mine water containing hazardous metal ions such as Iron, Zinc, Cadmium and Arsenic into the Carnon River and the Fal Estuary. As the mine water was carried by the Carnon River it caused serious pollution spreading its contents throughout the Restronguet Creek, into Carrick Roads and Falmouth Bay (Limited, n.d.) In 2000 it was commissioned that a treatment plant should be built at the site.
In 2010 Veolia Water Industrial Outsourcing were subsequently contracted to both operate and maintain this treatment plant.
UK Government Policy on Metal Mining
At present, mine operators must comply with all current legislation which prevents mine water from contaminating waterways. They are also responsible for cleaning any pollution that has occurred after mining at the site has ceased. However, many of these metal mines closed before the current laws are in place.
Prior to these laws, before 31st December 1999, mine operators could abandon a mine without notice and were not responsible for preventing the contaminated mine water from entering the waterways. For this reason the UK government set up the Water and Abandoned Metal Mines programme, providing funds to the Coal Authority and the Environment Agency to clean up pollution caused by historic metal mining.
The Water and Abandoned Metal Mines programme targets the most heavily impacted waterways in the UK which aims to achieve: cleaner rivers, more wildlife and more tourism and opportunities for industry which rely on clean rivers.
The annual running cost of this programme is £8.5m with Wheal Jane, the biggest and most expensive operation, costing the government about £1.5m a year to run, about 18% of the available fund.
Rest of the World
In order to show the suitability of our project in a wider context of that of the polluted sites in the Consolidated Mines, we have investigated the issues faced by other mining sites across the globe. We have focused on issues found in the USA and in the Philippines, as these cases show that this is an issue faced by developed and the developing world. However, this is not limited to these cases and it is a global issue where there have also been issues in Spain (Mateos, 2001), Romania (Johnston, 2002) and many other parts of the world.
There are numerous examples of where mining has led to metal ions leaching into water sources in the USA. One such example is the Eagle Mine, Colorado. This site operated from 1878 to 1977, mining zinc and other precious metals. The tailings contaminated ground water and then this water was discharged into nearby streams. The main metal ions of concern are arsenic, cadmium, copper and zinc, which all exceed water quality criteria, contaminating two private drinking water wells (Ceto et al 2000). After the mine flooded in 1984, causing a dramatic fish kill, the site was placed under the Environmental Protection Agency’s (EPA) Superfund site list and was slowing remediated. However, residents there are still worried about the potential of the mine to flood again (Coakley 2017). It is believed that the remediation of the site will never end, with remediation currently costing $1 million per year, with a total costs approaching $60 million. This process removes 221 gallons per minute or 116 million gallons per year of water from the Eagle River. Approximately 178 pounds of metals are removed per day, which are pressed into filter cakes that are then taken to a lined area at the Maloit Park site. The treated water is then returned to the Eagle River. (Boyd 2017). This process is clearly unsustainable as there is no aim to recycle these metals. The cost of the process means that there would be a great desire for a more cost effective method that can return the contaminated metals to be reused.
Similar examples of this can be found across America such as California Gulch located in the upper Arkansas River Valley in Lake County, Colorado. The site has been mined for lead, zinc and gold since the late 1800’s. The area was found to be contaminated with metals including cadmium, copper, lead and zinc, which have been discharged into the Arkansas River (Ceto et al 2000).
Following discussions with Greenpeace, they led us to issues currently created by the Lafayette Mine, Rapu Rapu (an island on the Philippines). It was mined for gold, silver, copper and zinc. The safeguarding in place for the environment was poor, causing cyanide and other contaminants to spill into the sea around the island, resulting in massive fish kills. The mine was subsequently closed. It was found that there were high levels of cadmium, copper and zinc at 0.846, 7.05 and 22.9mg/l respectively dissolved in the creeks near the mine (Brigden et al 2006). The acid mine drainage outflow into the sea caused coral death, which would cause devastation to the ecosystem that it supports.Treatment by neutralisation using limestone are not fully effective, and risk created (Cotter et al 2006). The contaminated water from Lafayette’s mineral processing facilities can spill into nearby creeks and into waterways that flow into the Albay Gulf (Sarmiento 2012). Our system would thus be implementable in this scenario as a system in place to clean the water in the event of spillages, as a safety net to prevent contamination spreading into the sea. This could be put in place in locations at risk of acid mine drainage outflow before it has happened or put in place when such an event occurs due to the fast setup and action of the system.
|Metal||Dissolved concentration in Mirikpitik creek
| Maximum concentration for drinking water
(Department of Health, Philippines, 2007)
Table 1: Showing the concentration of four of the metals present in the Mirikpitik creek, which is in the vicinity of the Lafayette mine in the Philippines, compared to the drinking water standards set by the Republic of the Philippine’s Department of Health.
Effects of Metal Ion Contamination on Ecology
Heavy metal environmental pollution is a global problem in estuarine, marine and coastal waters. It effects different organisms in different ways (Wickramasinghe, Mubiana, & Blust, 2017), degrading the marine environment ecology and causes dose-dependent effects (Wickramasinghe et al., 2017). Aquatic environments are susceptible to heavy metal pollution due to close and chronic contact with soluble metals (Wickramasinghe et al., 2017). Metals have been shown to accumulate in tissues in organisms exposed to increased metal concentrations (Wickramasinghe et al., 2017).
Metal pollution is largely associated with rapid population growth, industrial and daily human activities. Potential source of heavy metal ions in water include industrial waste and mine waste which release heavy metals previously stored in grounds and soils.
Metals, such as Cu, Cd and Zn, affect the photosynthetic molecular machinery of pirmary producers (Wickramasinghe et al., 2017). Photosynthetic primary productivity and pigmentation in algae decreases with increasing metal concentration (Wickramasinghe et al., 2017). In many ecosystem, algae are the primary producers and form the base of the food web, providing food and energy for all subsequent dependent herbivores and carnivores. Thus the metal ions can be transferred and concentrated along the food chain in a processes such as bioaccumulation and bio magnification.
When mussels, for example Mytilus edulis, consume algae via filter feeding (Riisgård, Egede, & Barreiro Saavedra, 2011) they bio accumulate pollutants contained in algal tissues and surrounding water (Nasci et al., 1999). Some biological effects of metal pollution include; inflammatory responses, parasite presence, degenerative changes (Nasci et al., 1999) and are intensified by their relatively low metabolic transformation rates (Galloway et al., 2002). Mytilus edulis is a commercially important species with around 185,000 tonnes of global aquaculture in 2014 (Kesy et al., 2017).
Consuming contaminated seafood can further impact human health as they alter cell processes and interfere with functions of proteins and enzymes. In 1956, a release of mercury in Japan bioaccumulated in shellfish which were subsequently eaten by people who further contracted disease from mercury poisoning (Boston University, 2017).
In addition, metals make their way into terrestrial ecosystems when they are absorbed by plants. Herbivores and grazers that consume plants incorporate metals into their issues. As these are hard to metabolise, they are passed along food chain. This is another route in which metals can be consumed by humans eating livestock.
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