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Determinating ecotoxicological risks of spreading dredged sediments on land. Pilot-assessment of de influence of soil characteristics on the bioavailability of metals and PAHs in field soils

Beoordeling van de ecotoxicologische risico's van de verspreiding van baggerspecie op land. Pilot-toetsing van de invloed van bodemeigenschappen op biobeschikbaarheid van metalen en PAKs in veldbodems

Synopsis

A pilot study has been executed to quantify the biological availability of heavy metals (Cd, Cu, Pb, Zn) and PAHs resulting from the deposition of dredged sediments on land soil. The idea is that biological availability is strongly influenced by soil type, so that environmental effects of deposited dredgings depend on both total contaminant concentrations and soil characteristics. The results of the investigations will eventually be used to construct a module to calculate the quantification of the total toxic pressure of deposited sediments. The aim of the current study was to obtain insight into the variation in bioavailability of compounds in different soil types. The sorption of PAH to soil was stronger than expected from data in the literature. This was associated with a relatively low PAH uptake in the worms. It is recommended to take the following issues into account in further research on the availability of toxic compounds in sediment after deposition on land: use sediments with higher contaminant loads (e.g., class 4), since this yields better interpretation possibilities for bioaccumulation studies (although extrapolation to lower contamination levels is required); use (earthworm) species that naturally occur in the relevant field soil types, and that perform well in bioassay conditions; sample sediments and soils at such locations that sampled soils encompass the full natural ranges of pH and organic matter contents in the field (to ensure broad applicability of the eventual results). The formulae for the eventual derivation of the bioavailability correction will be basic to the construction of a computer program. This program will calculate the local toxic pressure, as the net result of the locally available concentrations of toxic compounds and their mixture effects; the natural breakdown of organic contaminants will also be taken into account.
 

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