Team:Exeter/HP/Fieldtrips

Wheal Maid Field Trip

Our aim

It was important to us that the design of both our parts, our filter and the intended implementation for the project was a reflection of a real-world problem. This insight was largely given to us by stakeholders and the field trip, guided by Responsible Research and Innovation and the AREA framework, as it stressed the significance of society's role in science and it underlined the problem with innovating in an isolated manner. We organised a field trip to Wheal Maid mine to collect metal ion water composition data to tailor our synthetic biology project to real world conditions. We were motivated by our desire to base our science on our own data collected outside of the lab.

Wheal Maid forms part of the Consolidation Mine, part of the Cornwall and West Devon Mining Landscape World Heritage Site. Wheal Maid was mined 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. An investigation by the Environmental Agency to conduct an inspection into environmental quality, which took place in 2007, concluded that Wheal Maid is a contaminated site. It was also shown that the site is causing pollution of the St. Day Stream by leaching of arsenic, cadmium, copper, chromium, iron, lead, nickel and zinc through the toe of the lower lagoon. (Carrick District Council, 2008). For this reason we decided to conduct our primary field work at this site, collecting water samples from these lagoons.

Figure 1: One of the lagoons (top) and the pond (bottom) at the Wheal Maid mine site. (Photographed by Sean Large.)

Methods

In order to conduct our data collection safely, we completed the appropriate risk assessment forms. We used protocols 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. Sample analysis was performed using inductively coupled plasma optical emission spectrometry (ICP-OES), a capability offered to us through the use of equipment given to us by Greenpeace, which identifies the metal ion concentrations within water samples. Details of the protocols and risk assessments can be found on our safety page.

On 14th July 2017 we arrived at Wheal Maid with a PhD student from the Cambourne School of Mines at the University of Exeter, Miss Tomasa Sbaffi. She met us in order to help us with taking water samples due to her experience with the process and knowledge of the site. We sampled one of the lagoons and the pond shown in Figure 2.

The water bodies were sampled by taking 1L of water from each of the 4 sites at the lagoon (A-D) and the pond (E-H) as labelled in Figure 2.

Figure 2: Satellite map of Wheal Maid site with the lagoon marked A-D and the pond marked E-H.

Figure 3 was created using Vidana software to determine the percentage decrease in size of the lagoon and the pond since the Google Maps satellite photo was taken in January 2017. This reduction in surface area could be due to a number of factors, such as seasonality, which is likely to have caused an increase in the concentration of metal ions.

Figure 3: The percentage cover of the lagoon (left) and pond (right), sampled on 14th July 2017, has reduced by 78% and 77% respectively since January 2017. This area was determined from the location of the sampling sites around the edge of the lake and visually from Figure 2 (Geoplaner.com, 2017; Hedkey, 2017)

We then filtered 150 ml of each sample into three falcon tubes using a yellow 100 µm filter and then preceded to filter them further through a smaller 0.2 µm filter. We treated the blanks containing MiliQ 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.

Figure 4: Laura and Jake B preparing and analysing the samples at Wheal Maid. (Photographed by Sean Large.)

Results

pH of the Water Bodies

The pH of our samples can be found in table 1. An ANOVA (analysis of variance) was performed on the pH of the samples after storage from the different water bodies to see if there was a statistical difference between the two, shown in table 2.

Site pH
Lagoon Pond
N 24 11
Mean 2.80 2.77
Standard deviation 0.155 0.180
Standard error 0.0317 0.0514
Table 1: pH of the lagoon and pond sites at Wheal Maid.

Comparison ANOVA p-value Significant
Lagoon pH vs pond pH 0.640 No
Table 2: ANOVA statistic output testing the variation in pH of the lagoon and pond sites at Wheal Maid.

The ANOVA statistical test shows that there is no significant difference in pH between the pond and lagoon 2.

Metal ion composition ICP-OES results

           
Dissolved Metals Standards (mg/L)Lagoon (mg/L) Pond (mg/L)
Aluminium (Al) 0.200 6.726 50.584
Boron (B)0.300 0.0900.246
Cadmium (Cd) 0.003 0.007 0.027
Copper (Cu) 2.000 1.065 4.334
Iron (Fe) 0.200 3.445 16.307
Nickle (Ni) 0.020 0.023 0.197
Thallium (Ti) 0.0005 0.0280 0.0004
Zinc (Zn) 3.000 2.897 25.738
Table 3: Dissolved metal ion composition of samples taken from the Lagoon and Pond sites at Wheal Maid and analysed using the ICP-OES. Stars indicate which elements are found to have higher concentrations than the drinking water standards. (Defra, 2017; Lenntech.com , 2017; US EPA, 2015)

Figure 5: Metal ion concentrations at Wheal Maid showing those exceeding drinking water standards represented by the stars above the bars.

Discussion and Conclusion

Analysis of the results from the field trip to Wheal Jane helped inform our work in the laboratory. Specifically it allowed us to identify which of the metal binding proteins we wanted to use in our constructs in order to bind to metal ions that were significantly above their standards. The proteins we chose to investigate were; Mouse Metallothionein that binds to Cd, Cu and Zn), Synechococcus Metallothionein that binds to Cd and Zn, Synechococcus Plastocyanin that binds to Cu and a poly-Histidine tag inserted into the FimH protein to bind Ni.

References

Carrick District Council, Record of Determination of Wheal Maid Tailings Lagoons (2008) Available at: https://www.cornwall.gov.uk/media/3625647/2008-09-16-Record-of-Determination.pdf [Accessed 7 August 2017]

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]

Defra (2017). Drinking water inspectorate. [ebook] London, pp.1-5. Available at: http://Dwi.defra.gov.uk/consumers/advice-leaflet/standards.pdf.

Lenntech.com. (2017). WHO's drinking water standards. [online] Available at: http://www.lenntech.com/applications/drinking/standards/who-s-drinking-water-standards.htm [Accessed 12 Sep. 2017].

US EPA. (2015). National Primary Drinking Water Regulations | US EPA. [online] Available at: HTTPS://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations [Accessed 12 Sep. 2017].

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