Sediment Contamination and Toxicity in the Guadalquivir River (Southwest, Spain)

A segment of the Guadalquivir River was assessed between the Alcala del Rio dam and Seville through an integrative sediment quality assessment. Chemical concentrations of metals and toxicity under laboratory conditions were used as lines of evidence. A battery of bioassays with four organisms (the amphipod Ampelisca brevicornis, the bacteria Vibrio fischeri, the sea urchin Paracentrotus lividus, and the oligochaete Tubifex tubifex) exposed to sediment made it possible to determine the potential risk associated. The sediments from Seville and Alcala del Rio showed higher values of the concentration of most metals than the Algaba station, with Cu (35-37 mu g/g), Zn (70-75 mu g/g), Ni (23-26 mu g/g), and Pb (27-30 mu g/g) being the most abundant metals. An increasing toxicity gradient was shown downstream among the bioassays with the amphipod A. brevicornis, the fertilization test using the sea urchin P. lividus, and the freshwater worm growth T. tubifex. Conversely, an increasing toxicity gradient was shown upstream in the embryo-larval P. lividus development. The link between sediment contamination and toxicity makes it possible to obtain a gradient of contaminant concentration comparable with nationally and internationally widely accepted sediment quality guidelines in order to establish the risk associated with this area of study.