Team:Exeter/HP/Silver
Exeter
Wheal Maid field trip
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 that amalgamated in 1782 [1]
The Consols was a massively successful copper mine. Such was its fame that many other mines were opened using their name, with the hope to profit by association with the success story. Our field trip studied one of the Consols sites which is one of the largest causes of pollution in the area. Wheal Maid is an abandoned site that is owned by the Gwennap Parish Council, having been purchased for £1 from Carnon Enterprises [2]
The site was mined while the Consols were in operation until the 1870s, and then became site for taking fine-grained mineral processing wastes (tailings) from the mill facilities at the former Mount Wellington tin mine during the 1970s and 80s. A valley infill at Wheal Maid consists of two lagoons separated by three dams and contains approximately 220,000m3 of tailings. After pressure locally, the Carrick District Council asked the Environmental Agency to conduct an environmental quality inspection in 2007 [3]
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 soil. The controlled waters risk assessment show 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 further concludes that 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 [4].
The diagrams above and below show the nature of the land and indicate that a stream runs through or under the Wheal Maid site and joins up with another stream to form a river. This river contributes to the estuary
Planning
The aim of the field trip was to investigate the metal ion composition of the acid mine wastewater at Wheal Maid. The hypothesis is that the results from this investigation will show that the water is polluted and give us a focus for which heavy metals we would like to extract from the acid mine waste using our genetically modified E.coli model. Risk assessment forms were filled out to think about the possible hazards of the trip.
Field work risk assessmentA protocol was designed to enable efficient collection and filtration of the samples at the site before they were to be transported back and placed in a cold store for analysis.
Field work protocolThe field trip
14th Jully 2017 12:35am – arrived at the site A PhD student from the School of Mines at Falmouth University, Tomasa Sbaffi, met us to help us with sampling as she had regularly sampled this site and knew it well. We sampled one of the lagoons and the pond in the East.
We sampled Lagoon 2 by taking 1L of water from each of the 4 sites (1-4) as shown by the diagram. Additionally sampled the Pond by taking 1L from each of the 4 sites (5-8).
We then filtered 150ml of each sample in to 3 falcon tubes using yellow 100 um filter and then preceded to filter them further through a smaller 0.2 um filter. We treated the blanks containing Mili Q water as controls and processed them the same way as the samples. The pH of all of the samples was tested using litmus paper which all came out as ~pH 3. The samples were sealed in bags and transported back to Exeter to be placed in a cold room to await further analysis.
The diagrams below were created using Vidana software to determine the percentage decrease in size of the lagoon and pond since the Google Maps satellite photo was taken in 2017. The percentage cover of the lagoon in the photo (below, left), taken in 2017, is 23%. The percentage cover of the lagoon when it was sampled on 14th Jully 2017 was 5%. This was determined from the location of the sampling sites around the edge of the lake. Therefore the lake has declined by around 78% in volume since the picture was taken. This could be due to a number of factors such as seasonality. This is likely to concentrate the metal ions and pollutants in the water making the water more harmful to the environment. Similarly in the photo of the pool (below, right), the percentage cover changed from 22% to 4%, shows the pond has declined by around 81% in volume since the last picture was taken. Again, this could be due to factors such as seasonality.
Analysis of samples
We prepared the samples and ran them on the ICP-OES machine in the Geography department at the University of Exeter.
Standard Operating Procedures for sample analysis using the ICP-OES
*** Risk assessment **** Risk assessment for dealing with acids used in the SOP.
***Insert link to file COSHH_GEO_AM435_diluting acids_July 2016
Risk assessment for dealing with the standard stock metal ion solution for the ICP-OES.
*** insert link to file COSHH_GEO_AM432_ ICPOES_Greenpeace_GRL001+KB_Feb 2016 metal ion standards
*** Results***
References
[1] (http://www.cornwallinfocus.co.uk/mining/consols.php).
[2] (http://www.gwennap-parish.net/wheal_maid.html).
[3] (https://www.cornwall.gov.uk/media/3625647/2008-09-16-Record-of-Determination.pdf).
[4] (https://www.cornwall.gov.uk/media/3625647/2008-09-16-Record-of-Determination.pdf).
