Geochemical assessment of arsenic toxicity in mine site along the proposed Mineral Tramway Project, Camborne, Cornwall

Abstract

Many abandoned mine sites in Cornwall, UK, are characterised by elevated concentrations of arsenic which can cause contamination of surrounding soil and water resources. Often these sites have important historical and cultural value that requires access to be maintained, despite the potential toxicity of As. In west Cornwall, the potential for As contamination has been recognized within the Industrial World Heritage site focused on the Mineral Tramway and mining sites mines in the Gwennap and Camborne mining districts. The major abandoned mine sites, arsenic calciner and milling sites along a proposed tourist route in this area have been assessed for As toxicity and bioavailability taking into account the proximity of footpaths to areas of potential contamination. Arsenic concentrations up to 3.3% were found in soils along the proposed footpaths and exposed mine spoil, with 55% of all total As values above the UK criteria for contaminated industrial soil of 640 mg/kg in surface soil. Using a Physiologically Based Extraction Test (PBET), the maximum amount of As observed to be bioavailable varied from 4 mg/kg through to a maximum of 9,000 mg/kg with a positive correlation between total As concentrations and bioavailable As concentrations. Mineralogical and selective extraction evaluation identified that the PBET-released As is not so much associated with total As concentrations, but is positively correlated to As held within the weak ‘ionic-held’ As, strongly adsorbed As, As associated with amorphous iron and calcium oxide phases, and poorly crystallized As(V) salts. The data reported here have been used to develop a risk assessment of the sites and propose management strategies to mitigate these risks.

Arsenic concentrations, distributions and bioaccessibilities at a UNESCO World Heritage Site (Devon Great Consols, Cornwall and West Devon Mining Landscape)

“…We note that another facility in the Cornwall and West Devon Mining Landscape UNESCO World Heritage Site (a series of interconnecting mineral tramways 70 km to the west of DGC) that was opened to the public was subject to retrospective remediation measures, including restricting access to certain areas, removal of waste and covering tailings with top soil. This followed reports of As concentrations and bioaccessibilities in soils, tailings and overburden at targeted sites along the converted trails that were elevated (but whose median values were an order of magnitude lower than those reported here; 1770 g g -1 , n = 38) (Bowell et al, 2013).…”

Effects of pH on arsenic mineralogy and stability in Poldice Valley, Cornwall, United Kingdom

“…Arsenic may form toxic dust that can rest on garden soils and footpaths that young children may ingest via hand to mouth (Bowell, et al, 2013). Arsenic is a known toxin (Pascoe et al, 1994 ;Lorenzana et al, 1996;Farago et al, 1997;Kenyon et al, 2008;Pinyayev et al, 2011) and numerous studies have demonstrated higher As uptake in children (Eligali, 1994).…”

“…Towards the end of the nineteenth century, Cornwall dominated copper, tin and arsenic production globally (Buckley, 2005). Prolonged periods of mining without environmental regulations have had a significant impact to the surroundings (Farago et al, 1997;Camm et al, 2004;Bowell et al, 2013). One such mine, the Wheal Maid is located in the Poldice Valley in central Cornwall (Figure 1).…”

Defining an approach for contaminated land management in the context of mine reclamation in the historic Comstock mining district, Nevada, USA

“…historical management of mine waste or drainage (Lottermoser, 2003;Rytuba, 2005;Frau et al, 2009;González et al, 2012;Bowell et al, 2013). This can result in contamination of surrounding soil and water resources and may have associated ecological and human health impacts.…”

“…A nine-step selective extraction procedure was undertaken by ACZ laboratories, Colorado, on seven surface soil samples collected from mill sites to determine the partitioning and chemical nature of arsenic, mercury and lead within the Comstock district based on the scheme presented by Bowell et al (2013). The method targets soluble salts and adsorbed ions in addition to amorphous and crystalline phases using the extraction steps described in Table 1.…”