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PW20 New Approaches to Determining Soil and Sediment Exposures
(PW297) Use of bioassays and SPME to determine the toxicity of PAHs in polluted field soils.
Droge, STJ1, ter Laak, TL1, Hermens, JLM1, van Gestel, CAM2, 1 IRAS - Universiteit Utrecht, Utrecht, The Netherlands2 Vrije Universiteit, Amsterdam, The Netherlands
ABSTRACT- To evaluate the toxicity of field soils with complex PAH pollution, 28 day bioassays with the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus were combined with detailed chemical analysis of the soils. Fifteen PAHs were analysed in soil samples before and after the tests to determine whether toxicity could be attributed to the presence of PAHs. Toxicity tests on terrestrial organisms are usually based on total sediment concentrations only, whereas actual pore water concentrations are often closer related to the observed toxicity. Besides ethylacetate-soxhlet extraction, the solid phase micro-extraction (SPME) technique was used to determine the available, freely dissolved PAH concentrations. Because the soil properties of polluted soils differed from the standard soil used in many toxicity tests, several reference soils with a range of soil properties were tested as well. Although total sediment concentrations in several field soils were close to the sub(lethal) concentrations as determined in spiked toxicity tests, springtail reproduction was only affected by a few soils. In contrast to the results with PAH spiked soils, enchytraeid reproduction was a more sensitive parameter compared to springtail reproduction. The SPME results indicated that only for a very polluted soil, pore water concentrations of individual PAHs were above toxic aqueous concentrations, and furthermore never above water solubility. Moreover, the total amount of PAHs extracted with the SPME was estimated not to be in the range of levels inducing baseline toxicity for most soils. In combination with the bioassays, the SPME proved to be an easily applicable tool to determine the toxic potential of PAHs in soils.
Key words: bioassays, SPME, soil invertebrates, PAH
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