Authors:
PhD Eleanor van Veen | University of Exeter | United Kingdom
Prof. John Coggan | University of Exeter | United Kingdom
The metalliferous deposits of the Cornubian Orefield in Cornwall, UK have been mined since the bronze age. The most intense period of activity was during the late 18th and early 19th century when this area was renowned for the production of tin ores, copper and a range of other metals and metalloids including arsenic, lead and zinc. During a period of hard rock mining tailings were habitually discharged into river courses adjacent to the mines and processing areas. The suspended solids, dissolved and particulate materials followed the course of these rivers into their estuaries where they precipitated out and formed a layer of contamination that remains to this day (Camm and Scott, 2003). Potentially toxic trace elements such as arsenic, copper, zinc and lead are therefore present at extremely elevated concentrations in some Cornish estuarine sediments. Whilst much of the contamination has been shown by previous authors to form a layer of contamination at depth within the sediment profile (Pirrie et al. 2002), re-working of the sediments by tides and biota means that concentrations at the surface remain high. Many of these estuarine soils provide a habitat in which the halophyte plant, Salicornia europaea, thrives. This species has been suggested in the literature as a potential candidate for phytoremediation.
Results presented in this paper reveal the geochemical fractionation of contaminants in samples of the estuarine soils where S. europaea is growing. The BCR sequential extraction technique, described by Rauret et al. (1999) and Sahuquillo et al (1998), was applied to determine to what extent certain potentially toxic trace elements are present in the easily available, reducible, oxidisable or residual pools of metals and metalloids within the sediment substrate. Concentrations of these elements were also determined in samples of S. Europaea and conclusions on the plant bioaccessible fractions of these potentially toxic trace elements are drawn. The implications for the management of these sediments and the impact of any proposed remedial measures to ameliorate contamination are considered in the light of these results.
References:
Camm, S. and Scott, P. (2003) Camborne School of Mines online virtual museum.
Pirrie, D., Power, M., Rollinson, G., Hughes, S., Camm, S. and Watkins, D. (2002). Mapping and visualisation of historical mining contamination in the Fal Estuary, Cornwall, online resource, Camborne School of Mines.
Rauret, G., Lopez-Sanchez, J. F., Sahuquillo, A., Rubio, R., Davidson, C., Ure, A., & Quevauviller, P., (1999). Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials. Journal of Environmental Monitoring, 1(1): 57-61.
Sahuquillo, A., Lopez-Sanchez, J. F., Rubio, R., Rauret, G., Thomas, R. P., Davidson, C. M., & Ure, A. M., (1999). Use of a certified reference material for extractable trace metals to assess sources of uncertainty in the BCR three-stage sequential extraction procedure. Analytica Chimica Acta, 382(3): 317-327.