A weight of evidence approach to assess sediment quality in the Guadalquivir estuary

Abstract

The design of a weight of evidence (WOE) approach based on the use of the sediment quality triad to assess both the feasibility and the difficulty associated with this kind of method when used under high dynamic conditions is discussed. The Guadalquivir estuary was impacted by a mining spill from 1998 to 2002 and some effects are still found in the area. The use of the WOE in the estuary implies the integration of different lines of evidence that were previously used in the area (Gulf of Cádiz); including the sediment chemistry of metals and organics, acute toxicity tests, as well the variability in salinity and pH values currently measured in estuaries. It includes the use of chronic toxicity assays, the bioaccumulation measured under field and laboratory conditions and the histopathology measured in both laboratory-exposed and field-collected organisms. The correct description and selection of the lines of evidence complement the weight of evidence approach as a powerful tool to identify the range of environmental degradation (pollution) in the area. Integration of new lines of evidence such as chronic and bioaccumulation tests, and re-defining the original sediment quality triad to a new and ‘enhanced’ triad are introduced. Finally, some recommendations are cited for the design of WOE approaches using the sediment quality triad in environments of high natural variability, such as estuaries, and specifically to address the effects associated with the changes in salinity and pH values.