Assessment of ecotoxicological effects of creosote-contaminated lake sediment and its remediation

Abstract

There is an urgent need to develop accurate methods to identify risks associated with contaminated sediments and complex mixtures. Biological and chemical assessment of the adjacent environment can be considered an integral component of the remediation plan for any site heavily contaminated. An investigation was therefore conducted to identify any ecotoxicological risk associated with the creosote-contaminated sediment of Lake Jämsänvesi, in Central Finland and its remediation. Creosote is a widely used wood preservative containing about 85 % polycyclic aromatic hydrocarbons (PAHs) with various hydrophobicities. Desorption studies showed the resuspension of sediment spread toxic contaminants from sediment to the water layer - also in high mixing ratios. The elutriates contained high molecular weight PAHs and part of these are also carcinogenic compounds. The elutriates of the contaminated sediment were also toxic to photoluminescence bacteria (Vibrio fischeri) and waterfleas (Daphnia magna). Thus, the toxicity of elutriate in contaminated sediment increased when the elutriate contained a high total PAH concentration. The oligochaetes (Lumbriculus variegatus) accumulated PAHs from contaminated sediment. This suggested the bioavailability of PAHs from Lake Jämsänvesi to the benthic food chain, potentially resulting to the exposure and responses of fish (Onchorhynchus mykiss) characteristic to PAHs. The same PAHs were present in the mussel (Anodonta anatina) tissue and in settled particulate material during the remediation of Lake Jämsänvesi by capping. Remediation of Lake Jämsänvesi creosote-contaminated sediment may have also spread the contaminated material from the sediment to the water layer. Risk assessment and evaluation of remediation strategies at contaminated sites require estimation on both the total amounts of contaminants present and their potential for release from sediments to be evaluated.