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Wheal Maid field trip

Abstract

Mine waste has detrimental environmental effects by limiting vegetation growth (Craw & Rufaut, 2017), impacting species diversity and leaching into nearby water bodies and the environment (Leung, et al., 2017). Any toxic materials and metals affects the surrounding environment and can bioaccumulate in food webs. Affected organisms could be those used for human consumption such as fish, molluscs and crustaceans. This will in turn affect human health if consumed, highlighting this as an important issue that needs to be addressed. The water bodies at the Wheal maid mine site were investigated to understand the metal ion composition and pH of the water. Here we show that the pH was acidic and there were a mix of metals found in the water.

Introduction

Background

Figure 1: Wheal maid Lagoon 2

Figure 2: Wheal maid pond

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 (Anon., n.d.).

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 (Anon., 2008).

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. Tailings are known to limit plant establishment as they form an impermeable substrate, dune erosion removes juvenile plants and plant growth is limited by the Phosphorus bioavailability (Craw & Rufaut, 2017). There is some vegetation at Wheal Maid, as shown in Figures 1 and 2, but the cover is patchy and incomplete as the colonisation has been limited by low nutrient levels provided by the mine waste.

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 (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 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 (Council, 2008)

Figure 3: OSM map of Wheal Maid site with plotted sampling sites

Figure 3 and 4 show the nature of the land and indicate that a stream runs through or under the Wheal Maid site and joins up with the Carnon river. This river contributes to the Restronguet creek, leading to the Carrick Roads before ending in the English Channel. This highlights the issue of potential contaminants and pollutants leaching out of the waste site and into the water that will be carried out through the land and to the sea.

Figure 4: Zoomed out OSM map of Wheal Maid site with plotted sampling sites

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.

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 assessment

A 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 protocol

Methods

The field trip

14th July 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).

Figure 5: Satellite map of Wheal Maid site with plotted sampling sites.

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.

Results

The Figures 8 and 9 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. 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 for diluting acids used in SOP

Risk assessment for handling metal ion standard solution used in SOP

Results

Table 1: pH of the Lagoon and pond sites at Wheal Maid

Statistical test

An ANOVA (analysis of variance) was performed on the pH of the samples after storage from the different water bodies so see if there was a statistical difference between the two.

Table 2: ANOVA statistic output testing the variation in pH of the Lagoon and pond sites at Wheal Maid.

The ANOVA test (p=0.640) was not significant, therefore we can accept the null hypothesis that the there is no variation in the mean pH of the two sites as p>0.05. This means that these sites are of a similar pH and can be used as replicates when determining the metal ion composition or mine waste water, as they are so similar.

Metal ion composition ICP-OES results

Table 3: Dissolved metal ion composition of samples taken from Lagoon 2 and Pond sites at Wheal Maid.

Metals we have binding proteins for that are above drinking water standards

• Copper o DM Pond o TRM Lagoon 2 & pond

• Cobalt  no known standard

• Iron o TRM Lagoon 2 & pond

• Magnesium  no known standard

• Nickel o DM Lagoon 2 & pond o TRM Lagoon 2 & pond

References

CornwallinFocus.co.uk (2017) Mining in cornwall database - mine, cornwall. [Online] Available at: http://www.cornwallinfocus.co.uk/mining/consols.php [Accessed 07 2017].

Gwennap-Parish.net. ( 2008) wheal maid :: Gwennap Parish. [Online] Available at: http://www.gwennap-parish.net/wheal_maid.html [Accessed 07 2017].

Carrick District Council (1990). Environmental Protection Act 1990, Part2A – Section 78B Record of Determination of Wheal Maid Tailings Lagoons, Gwennap, Cornwall as Contaminated Land pp. 1-8 [Online] Available at: ttps://www.cornwall.gov.uk/media/3625647/2008-09-16-Record-of-Determination.pdf [Accessed 07 2017].

Craw, D. and Rufaut, C., (2017). Geochemical and mineralogical controls on mine tailings rehabilitation and vegetation, Otago Schist, New Zealand. New Zealand Journal of Geology and Geophysics, 60(-), p. 176–187.

Leung, H, Duzgoren-Aydin, N., Au, C., Krupanidhi, S., Fung, K., Cheung, K., Wong, Y., Peng, X., Ye, Z., Yung, K. and Tsui, M. (2016). Monitoring and assessment of heavy metal contamination in a constructed wetland in Shaoguan (Guangdong Province, China): bioaccumulation of Pb, Zn, Cu and Cd in aquatic and terrestrial components. Environ Science and Pollution Research, 24, p. 9079–9088.

Wheal maid photos credt: Sean Large

Screen shots of % cover credit: Hedkey, J. (2017). Vidana. Marine spatial ecology lab.

Screenshots of maps credit: Geoplaner.com. (2017). GPS Geoplaner online. [online] Available at: http://www.geoplaner.com/ [Accessed 07 Aug. 2017]