Heavy metals in organisms of the River Guadalquivir estuary: possible incidence of the Aznalcollar disaster

On the 25 April 1998, the giant holding pool of the Aznalcollar mine, owned by the Canadian-Swedish Company Boliden Ltd burst its banks; 5 million cub ic meters (6.7 million cubic yards) of sludge poured into the nearby River Guadiamar, which is a tributary of the River Guadalquivir (the main river o f the south Iberian Peninsula). Within hours of the accident, approximately 2.5 Hm(3) of acidic water with high concentrations of metals, especially Z n, had entered the River Guadalquivir. A biomonitoring program has been car ried out to evaluate the incidence of this spill on the fauna of the River Guadalquivir. Six sampling stations within the estuary of were established and six species of molluscs (Crassostrea angulata, Scrobicularia plana), cr ustaceans (Palameon longirostris, Uca tangeri, Melicertus kerathurus) and f ish (Liza ramada) were chosen for analysis. In the Portuguese oyster, Crass ostrea angulata, Cd and Cu concentrations were above the maximum allowed by the Spanish legislation for bivalves for human consumption (60 mu g.g(-1) wet wt. for Cu and 1.0 mu g.g(-1) wet wt. for Cd). The crustaceans Palaemon longirostris and Uca tangeri, also showed values above the legal limits fo r Cu (20 mu g.g(-1) wet wt.). An increase of the Zn levels was observed, as Zn concentrations in C. angulata were higher than those reported 30 years ago. The heavy metal concentrations in some of the organisms collected in t he River Guadalquivir were higher than in the Bay of Cadiz or the Mediterra nean Sea (clean sites), showing that this estuary was subjected to a heavy metal load. One month after the accident, concentrations of Zn were higher in C. angulata and in Palaemon longirostris compared with levels recorded o n the 25 April. Nevertheless, some organisms did not show a clear tendency during the sampling period, probably due to the fluctuations of environment al (salinity, temperature) and physiological variables that affect bioaccum ulation. (C) 1999 Elsevier Science B.V. All rights reserved.