An empirical approach to the determination of metal regional Sediment Quality Guidelines, in marine waters, within the European Water Framework Directive

Regional Sediment Quality Guidelines (SQG) for metals from the Basque Country (northern Spain) were determined. These guidelines are proposed to be used for management purposes, within the Water Framework Directive (WFD). SQG were determined on the basis of sediment chemistry, toxicity and benthic community disturbance, from 961 estuarine and coastal samples. The guidelines were calculated using a percentile approach (effect and non-effect data), following normalisation on the fine-sediment content and with non-normalisation. The feasibility of SQG was quantified by the incidence of adverse effects, that is, the ratio of effect/no-effect data, which increased significantly with increasing SQG ranges. The study proposes the following formula to calculate SQG: SQG(metal) = SQG(metal)* mu g.g(-1)/FC. 10(-2) (where FC is fine-sediment content and SQG* is the normalised SQG). The SQG* were 13.5 mu g.g(-1) for As, 1 mu g.g(-1) for Cd, 39 mu g.g(-1) for Cr, 55 mu g.g(-1) for Cu, 0.53 mu g.g(-1) for Hg, 23 mu g.g(-1) for Ni, 78 mu g.g(-1) for Pb and 249 mu g.g(-1) for Zn. The use of four different organisational biological levels ensures an improvement in the determination of metal regional SQG for the assessment of the chemical and physicochemical status in marine waters, within the WFD.