To establish concentration levels and patterns of distribution of lead pollution and associated indicative chronologies, soil samples and one sediment/soil core were taken at the mine, the site of Breadalbane’s crusher (Glengarry) and the site of the smelter (Dalree) in May 2010 (see site map, Fig. 2). Material for analysis was taken at the surface: 15, 30 and 45 centimetres and, where possible, at 60 cm depths. Sampling at the mine followed two parallel transects across the slope and was orientated north to south from the valley bottom to roughly a height of 550 metres on Minehill. Soil material was also sampled east of the mine site in coniferous woodland planted by the Forestry Commission in the mid-twentieth century and at two primitive dressing floors located at the adit mouths of two of the upper levels. At the crusher and smelter sites, six point samples were taken along east-to-west orientated transects at 100 metre intervals using a hand-held auger, with a seventh sample located at or near to the centre of the site. The point samples are marked by a small triangle and corresponding number on the site map. The auger samples were analysed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the lead concentrations (analysis carried out by the Institute of Aquaculture, University of Stirling). The cores were extracted using an adapted ‘golf hole’ corer. The precise locations within each of
the three sites, marked A, B and C on the map, were selected both because of the depth of material present and their respective stratigraphies, which potentially offered comprehensive coverage of the mining and metallurgical history of the sites. Soil profiles for three core samples were formally classified and recorded based on Munsell colour and hand texture; moisture content and pH were measured at 2 and 5 cm intervals respectively. The soil material was similarly analysed by ICP-MS for lead concentration and also for 210Pb dating (a method of dating the sediment in which the pollution was deposited) again at 2 cm intervals to establish an indicative chronology of pollution down the profile (Analysis carried out by the Environmental Radioactivity Laboratory (http:// www.erl.stir.ac.uk/), University of Stirling). The mine core (marked C on the site map) potentially encapsulated the entire 200-year history of mining activity, and to augment 210Pb dating an infra-red stimulated luminescence and optically stimulated luminescence (IRSL-OSL) non-calibrated profile was also established. This analysis determines the order in which the sediment containing the lead pollution was deposited over time (Sanderson & Murphy 2010). Finally, samples were also taken at all three sites for thin section micromorphology, allowing analyses of the micro-organisation of the soil and facilitating greater understanding of the location of lead within the profile. The level of background contaminants in Scottish soils commissioned by the Scottish Environment Protection Agency and reported by the Macaulay Institute in 2002 provide the reference point for the examination of lead contamination at the mine (Paterson et al. 2002). The Tyndrum soils fall with the Strichen Soil Association (soils derived from acid rocks, mainly acid schists, schistose grits and granulites of the Dalradian). The reported lead concentrations for Strichen, for mineral surface horizons range from 8.8 to 113 milligrams per kilogram, for organic surface horizons 1.9 to 245 mg per kg, and for subsoil or B horizons, the range is 10 to 80 mg per kg (Paterson et al. 2002, p. 50). Given the mineralogy at Tyndrum, concentrations at the top end of these ranges could be expected. The
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