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2D - Mechanisms of toxic action (TU4/14) Chronic effects of homocyclic and N-heterocyclic PACs on Folsomia candida and Enchytraeus crypticus. Droge, Steven1, Bleeker, Eric1, 2, Van Gestel, Cornelis1, Wiegman, Saskia2, Kraak, Michiel2, 1 Vrije Universiteit Amsterdam, Amsterdam, The Netherlands2 Universiteit van Amsterdam, Amsterdam, The Netherlands ABSTRACT- Contamination of (industrial) soils with polycyclic aromatic compounds (PACs) is a well recognized environmental problem. In contrast, literature on ecotoxicological effects of homocyclic PACs in soils is fragmentary whereas data on heterocyclic PACs is virtually absent, hampering reliable risk assessment. Therefore the present study focuses on soil toxicity of 6 homocyclic PAHs (ranging from 2 to 5 fused rings) and 3 nitrogen-heterocyclic PACs (2 and 3 ringed structures). Two terrestrial invertebrates, the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus, were exposed for 28 days in standardized natural soil, spiked with the individual test compounds. The effects on survival and reproduction were recorded. By using similar test conditions, the results for both test organisms could be directly compared, showing a significantly higher sensitivity to all PACs for F. candida than for E. crypticus. For both species the heterocyclic PACs were more toxic than their homocyclic analogues, but also differences in toxicity between closely related compounds such as isomers were observed. The obtained LC50 and EC50 values of these PACs were related to molecular properties of the compounds in order to determine key factors which describe toxicity of PACs to soil invertebrates, thus explaining differences in toxic mode of action between isomers and homocyclic and heterocyclic compounds. Implications for risk assessment are discussed. Key words: soil invertebrates, PAH, chronic toxicity, risk assessment |
