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1D - Soil and Sediment Contamination (TUP/14) Stratigraphy of wood-related sterols in sediments historically contaminated by pulp and paper mill effluents. Oikari, Aimo1, Lahdelma, Ilpo1, 1 University of Jyväskylä, Jyväskylä, Finland ABSTRACT- Sterol concentrations related to process changes and wastewater treatment of pulp and paper industry were studied in two Finnish lakes, one with stratified sediment type (Central Lake Päijänne) and another one with transportation sediment (Southern Lake Saimaa). The sediment samples were extracted in a Soxhlet apparatus with hexane:acetone (2:1, v/v) and sterols were further separated in a silica gel column with chloroform. Seven sterols (cholesterol, cholestanol, campesterol, campestanol, stigmasterol, Key words: wastewater treatment, |
-sitosterol and stigmastanol) were identified and quantified by GC/MS technique. In the sediment of the Central Lake Päijänne the maximum sterol concentration (ca. 2.0 mg/g dw) was found from the depth of 12-15 cm, dating back to 1970s. Process change from sulphite pulping to mechanical pulping and introduction of secondary wastewater treatment have, among other pollutants, lowered discharge of sterols and, therefore the concentrations in the uppermost sediment (0-3 cm) were about 10 % of the historical maximum. In Southern Lake Saimaa, however, the highest sterol concentration (ca. 1.8 mg/g dw) was found in the surface sediment (0-5 cm), despite the fact that mills modified their bleaching technique and utilized the activated sludge process for the wastewater treatment in the beginning of 1990s. One apparent explanation for this difference is, besides the type of sediment dynamics, the logging and storage of wood furnish at the Southern Lake Saimaa. The toxicity of sediment elutriates (sediment + water; 1:4, v/v), measured by bioluminescence inhibition of Vibrio fisheri, was significantly higher in deeper parts of the sediment (9-24 cm) from the Central Lake Päijänne than in other sediment samples, indicating the influence of previous pulp processing. However, no direct association was found between the concentrations of sterols and the whole sediment toxicity.