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Development of analytical methods for the assessment of biologically relevant contaminants in soils

Final report 07 OTX 03
: Koerdel, W.; Wahle, U.; Debus, R.; Hund, K.
: Fraunhofer-Institut für Umweltchemie und Ökotoxikologie -IUCT-, Schmallenberg

Bonn, 1996, 209 pp.
Research Report
Fraunhofer IUCT ( IME) ()
bioavailability; ecotoxicological testmethod; extract; habitat function soil; soil extraction method

Assessment of soil quality based exclusively on chemical analysis is not feasible, because it is impossible to measure all chemical substances including their degradation products which may occur. Therefore risk assessment can only consider those substances and concentration ranges which can actually be detected by chemical analysis. Usually, in hazard assessment effect concentrations (ecotoxicity data) are related to exposure data (environmental resp. soil concentrations of the respective substance). Such a risk assessment is highly uncertain because data on ecotoxicity for the compartiment soil are rare and insufficient. Besides the difficulties associated with the determination of mixtures of substances in the soil, it is nearly impossible to determine the substance concentrations associated with the different exposure pathways, i.e. pore water, soil air, uptake of contaminated food, and contact with particle-bound substances. The same is true for the assessment of synergistic or an tagonistic actions using substance data. These difficulties can be minimized by combining chemical and ecotoxicological analysis. In the study separated batches of brownsoil, Lessive and Tschernosem were hornogenously contaminated with linclane and PCP at concentrations of 10 mg/kg and 100 mg/kg soil dry weight and with 50 and 500 mg/kg dry weight PCB 52. After 4 weeks aging, the contaminated soils were filled into microcosms. Samples were taken on days 0, 14, 28 and 56. Using these contaminated soils, different extraction solutions and methods were tested. The toxicity of the substances in the soils were tested using several representative soil organisms. Single species tests with aquatic and terrestric organisms were used for determining the toxicity of the soil extracts. Conclusions: I. For the readily water soluble PCP the effects observed in tests with soil extracts were in good agreement with the data obtained directly in the soil. The same was true for lindane, which has a rela t ively low water solubility, but only with repect to early sampling dates and the high concentration. II. An impairment of the habitat function can be assumed if effects are observed in the aquatic tests. If no effects are detected, habitat function can still be disturbed. This must be kept in mind especially when dealing with substances of poor water solubility.