Deriving sediment quality guidelines in the Guadalquivir estuary associated with the Aznalcollar minig spill: A comparison of different approaches

Abstract

Concentrations of heavy metals (Fe, Zn, Cd, Pb, Cu and Mn) and sediment toxicity tests (mortality of amphipods, Ampelisca brevicornis, of clams, Scrobicularia plana, and of fish, Solea senegalensis) were used to derive sediment quality guidelines (SQGs). The approaches are based on the determination of LC50, on the application of a multivariate analysis (MAA), and on the Threshold Effect Level Quotients (TELQs). All approaches lead to consistent SQGs. The range of concentrations established with MAA results in narrower uncertainty ranges. Sediment toxicity estimated by TELQs is in good agreement with that determined experimentally. In terms of the toxic mud concentration, the maximum and minimum LC50s (for fish EC50s) are 1.07% and 0.44% for amphipods, 5.75% and 1.25% for clams, and 7.24% and 1.97% for fish, based on dry weight. However, heavy metal concentrations or ranges should be used only as a first tier in a "weight-of-evidence" approach to determine the environmental quality in aquatic systems. The use of SQGs for the management of these systems should be taken with care, especially those used for the management of dredging processes.