PARENT SESSION

1D - Soil and Sediment Contamination
Poster Hall
8:30 AM - Tuesday, 29 April 2003
Chair: Van Noort, P.¹, ¹
Co-chair: Gerhardt, A.², Gerhardt, A.², ²

(TUP/2) Arsenic rich ironplaque on macrophyte roots – a long term problem for Donana National Park, Spain?

Taggart, Mark¹, Osborn, Daniel², Mateo, Rafael³, Meharg, Andrew¹, ¹ University of Aberdeen, Aberdeen, Scotland, Scotland² Centre of Ecology and Hydrology, Huntingdon, England, England³ Universitat Autònoma de Barcelona, Barcelona, Spain

ABSTRACT- In April 1998 an acid mine tailings lagoon failed and released an estimated 5-6 million m³ of acidic, metal rich sludge and water into the Rio Guadiamar in SW Spain. This major local river supplies freshwater to the internationally important Donana World Heritage Site. Some 2700ha of protected parkland in Donana were contaminated by the spill. Despite clean-up, a residual pollutant load still exists, and the long term effects on Donana are yet to be realised. The waste was rich in metals such as Pb and Zn, and also contained up to 0.6% arsenic. In autumn 2001, samples of sediments, Scirpus maritimus and Typha dominguensis were taken and analysed for total As. Levels ranged from 1.6-532mg/kg^-1 in the sediments, 1.4-572mg/kg^-1 and 1.7-355mg/kg^-1 in Scirpus sp. and Typha sp. roots, 0.1-123mg/kg^-1 and <0.1-140 mg/kg^-1 in Scirpus sp. and Typha sp. rhizomes, and <0.1-8.1mg/kg^-1 and 0.3-28.4mg/kg^-1 in Scirpus sp. and Typha sp. stems. Mean levels associated with the roots of Scirpus sp. and Typha sp. were up to an order of magnitude greater than in the sediment from which they came. SEM-EDAX analysis of roots with up to 572mg/kg^-1 has shown easily detectable particles rich in As, (estimated to contain up to 1% As), associated with root surfaces. These particles form part of an ironplaque on the root surfaces, but are geochemically distinct in that areas high in As correspond with areas high in phosphorous. Arsenate, an analogue of phosphate, is perhaps substituting within the matrix of the iron-phosphate plaque. The importance of this process in terms of its potential impact on food chains remains unknown. In Donana, birds such as Greylag Geese (Anser anser), and the rare Purple Gallinule (Porphyrio porphyrio), feed on the rhizomes and roots of these species and may therefore be susceptible. Geese faeces sampled in 2001 have been found to contain up to 14mg/kg^-1 of As.

Key words: donana, arsenic, ironplaque, macrophytes