Biomonitoring of trace elements in the leaves and fruits of wild olive and holm oak trees Paula Madejo ´n 1 , Teodoro Maran ˜o ´n T , Jose ´ M. Murillo IRNAS, CSIC, P.O. Box 1052, 41080 Sevilla, Spain Received 22 October 2004; accepted 18 February 2005 Available online 10 May 2005 Abstract Biomonitoring of trace elements is essential to assess ecosystem health, in particular in landscapes influenced by human activity. The Guadiamar Valley (SW Spain) was polluted in 1998 by a spill from an open-pit pyrite mine affecting about 55 km 2 . In this paper, we used two common species of tree, namely wild olive and holm oak, to biomonitor the concentration of nine trace elements–As, Cd, Cu, Fe, Mn, Ni, Pb, Tl and Zn–in this spill-affected area over the 3-year period 1999–2001. We analysed the leaves and fruits of trees growing in the spill-affected terraces, and compared them with adjacent trees in the non-affected upper terraces. The main trace elements polluting the soil were Zn, As, Pb and Cu. In general, the oak leaves were richer in trace elements than the olive leaves, reaching phytotoxic levels for As and Pb, while the olive fruits (pulp) were more polluted than the oak seeds (protected inside a hard pericarp), reaching toxic values for Cd and Pb. The concentration of trace elements in the leaves and fruits decreased with time and, in consequence, the toxicity risk to the food web diminished. D 2005 Elsevier B.V. All rights reserved. Keywords: Heavy metal; Cadmium; Zinc; Guadiamar; Mediterranean trees, Olea europaea; Quercus ilex 1. Introduction There is a general decline in forest ecosystem health throughout Europe. About 20% of the 311,726 trees monitored in 2003, distributed over 39 countries of the European network system, showed symptoms of damage. The most important causes included extreme weather conditions, insect and fungi attack, and air pollution (Lorenz et al., 2004). Besides this general trend, on a continental scale, there are other detrimental factors for forest ecosystem health such as fire, urbanisation, pollution from chemical plants and mine tailings acting on a local scale. A severe pollution event, the Aznalco ´ llar spill from an open-pit pyrite mine, occurred in 1998 in the Guadiamar Valley (SW Spain). About 55 km 2 of land, including riparian forests and oak woodlands, were 0048-9697/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2005.02.028 T Corresponding author. Tel.: +34 95 4624711; fax: +34 95 4624002. E-mail address: teodoro@irnase.csic.es (T. Maran ˜o ´n). 1 Present address: School of Biological and Earth Sciences, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK. Science of the Total Environment 355 (2006) 187– 203 www.elsevier.com/locate/scitotenv