Oliver H. J. Szolar

Toxicity testing of 16 priority polycyclic aromatic hydrocarbons using Lumistox.

Hazard assessment of industrial sites contaminated with coal tar and its products usually focuses on selected pollutants such as the 16 polycyclic aromatic hydrocarbons (PAHs) prioritized by the U.S. Environmental Protection Agency (U.S. EPA). The aim of this study was to investigate to which extent these 16 PAHs contribute to the Vibrio fischeri bioluminescence inhibition measured by the acute Lumistox luminescent bacteria test. Five of the 16 PAHs-naphthalene (NAP), acenaphthylene (ACY), acenaphthene (ACE), fluorene (FLU), and phenanthrene (PHE)-revealed inhibiting effects when measuring saturated aqueous solutions of these compounds. However, in elutriates of PAH-contaminated soils, the amount of leached PAHs was very low, and the 16 PAHs did not considerably contribute to the observed bioluminescence inhibition. Nevertheless, bioluminescence inhibition was higher for elutriates with increased PAH concentration indicating the presence of other toxicants that co-occur with the 16 PAHs. No evidence was observed for increased bioluminescence inhibition due to synergistic effects among PAHs as calculated on the basis of toxic units for an aqueous solution containing all 16 priority PAHs. Data suggest that the U.S. EPA PAHs play only a minor role in causing acute toxicity to V. fischeri when exposed to aqueous elutriates of PAH-contaminated soils.

Detoxification of wood hydrolysates with wood charcoal for increasing the fermentability of hydrolysates

An effort was made to develop wood charcoals to remove inhibitors such as furan and phenolic compounds in wood hydrolysates for improving the fermentability of the wood hydrolysate. Wood charcoals prepared at various temperatures were found to selectively remove only the inhibitors without reducing the levels of fermentable sugars. It was also found that the wood charcoals prepared at higher temperature had enhanced ability to remove inhibitors, compared to wood charcoals prepared at lower temperature. The fermentability of the hydrolysates had been improved by the wood charcoal treatment. A closer investigation on the fermentability showed that hydrolysates treated with wood charcoals prepared at higher temperature could attain higher fermentability, compared to hydrolysates treated with wood charcoals prepared at lower temperature. This may be related to the mechanism of removal of inhibitors by the wood charcoals.

Behavior of PAHs during cold storage of historically contaminated soil samples

The stability of historically polycyclic aromatic hydrocarbon (PAH)-contaminated soils during cold storage was investigated. Samples from two former manufactured gas plants exhibited quantitative recoveries of PAHs over the whole period of sample holding at 4 degrees C in the dark (8-10 months), whereas significant losses of PAHs were observed for soils received from a former railroad sleeper preservation plant with low molecular weight compounds being notably more affected compared to heavier PAHs. Already after 2 weeks of holding time, 3-ring PAHs in one of theses samples were down to 29-73% of the initial concentration and significant losses were observed for up to 5-ring compounds. Dissipation of PAHs was found to be predominantly due to aerobic microbial metabolism since sodium azide poisoned samples showed quantitative recoveries for all PAHs over the entire storage time of 3 months. A similar stabilizing effect was observed for freezing at -20 degrees C as means of preservation. Except for acenaphthene, no significant loss for any of the PAHs was observed over 6 weeks of holding time. Eventually, selected chemical, physical, and biological parameters of two soils were investigated and identified as potential indicators for the stability of PAH-contaminated soil samples.

Use of Bioassays in Determining the Ecotoxicity of Industrial Soils

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous contaminants [1] which are of concern due to their mutagenic [2] and epigenetic [3] characteristics. Because of their environmental and biological importance, 16 PAHs have been included in the U.S. Environmental Agency’;s priority list of pollutants.

Application of Bioassays for Site Specific Risk Assessment

Bioassays are widely applied to measure the toxic effects of aquatic samples such as surface water and groundwater, leachates and elutriates, as well as sediments, sludges, and soils. Contrary to (eco)toxicity tests, which translate single chemical concentrations into toxic effects (dose-response relationship giving EC50, NOEC, etc.), bioassays are applied to samples from contaminated sites without detailed knowledge of qualitative and quantitative extent of pollution [1]. Depending on the type of test, bioassays may deliver fast and relevant information on adverse effects that contaminated samples pose to certain test organisms. Currently, bioassays are used to prioritize contaminated sites and to establish site specific remediation goals.