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(351) Environmental risk of linear alkylbenzene sulphonates (LAS) in agricultural soils. Jensen, John1, Løkke, Hans1, Holmstrup, Martin1, Krogh, Paul Henning1, Elsgaard, Lars2, 1 2 ABSTRACT- LAS are major ingredients of synthetic detergents and surfactants and used world-wide for both domestic and industrial applications. LAS are easily degraded under aerobic conditions, but not degraded under anaerobic conditions. Therefore, they can be found in high concentrations in sewage sludge and may hence enter the soil compartment as a result of sludge application. In the present risk assessment a probabilistic approach has been used to assess the risk of LAS to soil ecosystems. By use of a log-normal distribution model the Predicted No Effect Concentration (PNEC) for soil fauna and plants were estimated. Due to the heterogeneous endpoints for micro-organisms including functional as well as structural parameters, the use of sensitivity distributions is not considered applicable to this group of organisms and a direct expert evaluation of toxicity data was used instead. The soil concentration after sludge application (PEC) was predicted for a number of scenarios and used in the risk characterisation and calculation of risk quotients (RQ = PEC/PNEC). In Denmark, the initial risk ratio would reach 1.5 in a realistic worst case consideration. For countries not having similar sludge regulations the estimated risk ratio may initially be considerably higher. However, even in the most extreme scenarios, the level of LAS is expected to be well beyond the estimated PNEC one year after application. The present risk assessment therefore concludes that LAS does not pose a significant risk to fauna, plants and essential functions of agricultural soils as a result of normal sewage sludge amendment. This has been supported by long term field studies monitoring the effect of sewage sludge on the soil microarthropod community. Key words: Detergent, Sewage sludge, Terrestrial risk assessment , Field studies |
