Toxicological Tests for Minimizing Risks at Contaminated Sites during Clean Up

The microbiological potential of the contaminated site was assessed using simple indicative parameters of microbiological degradation (nitrate, sulfate and redox potential). The convenient measurements, provided by this method facilitated a rapid estimate of the oxidative and microbiological conditions of the groundwater. The results show that dissolved oxygen in the groundwater under hotspot areas and along the contamination plume was depleted and that most nitrate and sulfate had been consumed. These observations suggest that microbiological degradation processes could be further activated by adding adequate nutrients.
In addition to analytical work, assays for luminous bacteria were conducted, to add an eco-toxicological parameter to the assessment of the site as-is status. This parameter may also be used for future monitoring of the remediation success. Results of the luminous bacteria tests were found to mirror contaminant levels observed in the ground water of the gas works site.
The physico-chemical and eco-toxicological data obtained during the groundwater assay were displayed in two-dimensional format by means of special graphical software, providing a means to visualize the concentration centers of individual contaminants.
As part of the project FAMOS, IFA-Tulln conducted bio-reactor degradation tests with contaminated soil material originating from two hotspots. The samples were extensively analyzed and toxicologically monitored through chemical analysis of selected distinctive parameters and a bioassay battery especially assembled for this purpose by the author. Measurement of the selected 16 hetero-PAHs was included with other analytical parameters and in analogy with the 16 EPA-PAHs, a composite parameter Σhetero-PAHs was devised. This parameter could then be compared and contrasted with the total 16 EPA-PAHs (ΣEPA-PAHs). The Σhetero-PAHs was frequently within the same order of magnitude as the ΣEPA-PAHs, which accentuates the im-portance of the hetero-PAHs that have hitherto only found little attention.
Good agreement was found between the eco-toxicology research with the chosen bioassays (luminous bacteria, Thamnotoxkid FTM, algae and daphnia tests) and the analytically determined concentration of pollutants. In all analyzed samples, decreasing concentration of the selected contaminants (Σhetero-PAHs, ΣEPA-PAHs, ΣCyanide and ΣBTEX) was accompanied by a decrease of toxicity with the biological test systems.
This suggests that, with high probability, no elevated toxicity may be expected during the degradation processes because of toxic metabolite formation and/or elevated bioavailability of pollutants.
The described method is very well suited for assessing future changes in groundwater during and after a hotspot remediation and as well, for toxicological monitoring of an ongoing in-situ-remediation at the site of the Gasworks Simmering. As a result of the applied combination of biological test systems and state-of-the-art analyses, even complex mixtures of contaminants can be well defined and toxicologically evaluated.

 

- the paper is written in german -

 

 

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