Sediment quality assessment and dredged material management in Spain: Part II, analysis of action levels for dredged material management and application to the bay of Cádiz

Abstract

When sediments are removed from aquatic bottoms, they turn into dredged material that must be managed, taking into account its environmental impact. In Part II of this 2-part paper addressing sediment quality assessment and dredged material management in Spain, legislation and criteria used to regulate dredged material disposal at sea in different European countries are reviewed, as are action levels (ALs) derived by different countries used to evaluate management of dredged sediments from Cádiz Bay located on the South Atlantic coast of Spain. Comparison of ALs established for dredged material disposal by different countries reveals orders of magnitude differences in the values established for the same chemical. In Part I of this 2-part paper, review of different sediment quality guideline (SQG) methods used to support sediment quality assessments indicated a great heterogeneity of SQGs, both with regard to the numeric values for a particular chemical and the number of substances for which SQGs have been derived. The analysis highlighted the absence of SQGs for priority substances identified in current European Union water policy. Here, in Part II, the ALs are applied to dredged sediments from Cádiz Bay (South Atlantic coast of Spain), evidencing that the heterogeneity of ALs implemented in the reviewed countries could determine different management strategies. The application of other measurements such as bioassays might offer information useful in identifying a cost-effective management option in a decision-making framework, especially for dredged material with intermediate chemical concentrations.

Harmonised framework for ecological risk assessment of sediments from ports and estuarine zones of North and South Atlantic

“…The process for deriving national ALs or SQGs varies among countries. Most European countries use empirical approaches, based principally on comparisons of polluted sediments with contaminant levels in reference areas or local background concentrations (Alvarez-Guerra et al 2007). A different approach is also employed in the derivation of sediment guidelines, which takes into account the effects of ranges of contaminants' concentration to the biota in the derivation process; as these SQGs are based on risk information, typically conservative by design, and intentionally overprotective (O'Connor 2004), the ecological risks are usually considered negligible in instances when levels of contaminants are below SQGs-low (EC/OME 2008).…”

“…The assessment of chemicals in sediments has been developed during the past thirty years (Wenning et al 2005); at a regulatory level, it has been traditionally performed based on measurements of concentrations of selected contaminants and comparing them with numerical sediment quality standards (Alvarez-Guerra et al 2007). However, chemical analyses performed alone do not accurately predict environmental risks since the simple measurement of level of contaminants in sediments does not provide important information, such as the bioavailability of these compounds and mixture effects of interactions in a contaminants' mixture (synergism, antagonism or addition) (Stronkhorst et al 2003).…”

Using Various Guidelines and Approaches for the Assessment of Marine Sediment Quality

“…In Europe, for the management of dredged material, most countries have established action levels (ALs) that define classes of contamination for dredged material (Casado-Mart ınez et al, 2006;Alvarez-Guerra et al, 2007). The most common approach involves two ALs in which three classes are defined.…”

Integrated physical–chemical and ecotoxicological approach in the management of dredging sediments from Palermo Harbour

“…However, chemical characterisation alone does not provide specific biological information about the potential hazard to organisms [9] and is not sufficient to predict environmental risk [3].…”

“…A more accurate assessment of sediment contamination and its relationship to environmental risk should be based on a multidisciplinary approach, which integrates different lines-of-evidence (LOE), such as physical and chemical analysis and bioassays to assess toxic effects [9,10].…”