|
(38-44) Designing an ERA based protocol for the decision-making process in the management of contaminated sediments . Iglesias, Javier1, Antepara, Marķa1, Cagigal, Ekain1, Bonilla, Alberto1, Urzelai, Arantzazu*,1, 1 LABEIN Technological Centre, Cuesta de Olabeaga 16, Bilbao, Spain ABSTRACT- A general decline in surface water quality is a widespread phenomenon throughout Europe. Many efforts and investments are made to improve its quality and decrease the environmental hazard associated. This paper shows the first-phase results of an ambitious project aiming at the regeneration of the river-estuary system of the Nervion river, affected by the heavily industrialised and populated metropolitan area of Bilbao. The study included an extensive monitoring program of the sediments along the river, which comprised 62 sampling points in an area of 12 km long. At each sampling point, samples were taken from different depths, which resulted in a total of 216 samples for chemical characterisation. Quantified pollutants in the sediment samples included heavy metals and organics. In addition, leaching behaviour and mobility of the sediments were determined using batch and column leaching tests as well as sequential extraction tests. These tests were performed on 12 mixed samples. Ecotoxicity of these extracts was examined by short-term bioassays (Microtox). Analytical results show that the most polluted sediments correspond to the main industrialised areas, mainly located in the central transect of the study area. A special mention requires the sediments accumulated in several inner harbours. These sediments showed the highest pollutant concentrations. However heavy pollution was restricted to the deeper layers, while in top of the sediment column detected concentrations were in the range of the values found in less polluted transects. From a management point of view, this implies that there is no legal requirement for the dredging of these deep sediments. Leaching tests showed that the mobility of organics is in general "very limited". The absence of toxic effects observed in the extracts agrees with these results. With regard to heavy metals, Cd and Zn were found as mobiles fractions while mercury, the main inorganic pollutant of concern, only was detected as less mobile chemical species. Ecotoxicity of inorganic leachates do not correlate well with mobility data. Based on these results and on literature data, a conceptual model and a protocol for the assessment of ecological risks derived from non-dredged sediments is proposed. Key words: sediment pollution, mobility, ecotoxicity, ERA protocol |
