AhR agonist and genotoxicant bioavailability in a PAH-contaminated soil undergoing biological treatment
- First Online:
- 380 Downloads
Background, aim, and scope
Degradation of the 16 US EPA priority PAHs in soil subjected to bioremediation is often achieved. However, the PAH loss is not always followed by a reduction in soil toxicity. For instance, bioanalytical testing of such soil using the chemical-activated luciferase gene expression (CALUX) assay, measuring the combined effect of all Ah receptor (AhR) activating compounds, occasionally indicates that the loss of PAHs does not correlate with the loss of Ah receptor-active compounds in the soil. In addition, standard PAH analysis does not address the issue of total toxicant bioavailability in bioremediated soil.
Materials and methods
To address these questions, we have used the CALUX AhR agonist bioassay and the Comet genotoxicity bioassay with RTL-W1 cells to evaluate the toxic potential of different extracts from a PAH-contaminated soil undergoing large-scale bioremediation. The extracts were also chemically analyzed for PAH16 and PCDD/PCDF. Soil sampled on five occasions between day 0 and day 274 of biological treatment was shaken with n-butanol with vortex mixing at room temperature to determine the bioavailable fraction of contaminants. To establish total concentrations, parts of the same samples were extracted using an accelerated solvent extractor (ASE) with toluene at 100°C. The extracts were tested as inducers of AhR-dependent luciferase activity in the CALUX assay and for DNA breakage potential in the Comet bioassay.
The chemical analysis of the toluene extracts indicated slow degradation rates and the CALUX assay indicated high levels of AhR agonists in the same extracts. Compared to day 0, the bioavailable fractions showed no decrease in AhR agonist activity during the treatment but rather an up-going trend, which was supported by increasing levels of PAHs and an increased effect in the Comet bioassay after 274 days. The bio-TEQs calculated using the CALUX assay were higher than the TEQs calculated from chemical analysis in both extracts, indicating that there are additional toxic PAHs in both extracts that are not included in the chemically derived TEQ.
The response in the CALUX and the Comet bioassays as well as the chemical analysis indicate that the soil might be more toxic to organisms living in soil after 274 days of treatment than in the untreated soil, due to the release of previously sorbed PAHs and possibly also metabolic formation of novel toxicants.
Our results put focus on the issue of slow degradation rates and bioavailability of PAHs during large-scale bioremediation treatments. The release of sorbed PAHs at the investigated PAH-contaminated site seemed to be faster than the degradation rate, which demonstrates the importance of considering the bioavailable fraction of contaminants during a bioremediation process.
Recommendations and perspectives
It has to be ensured that soft remediation methods like biodegradation or the natural remediation approach do not result in the mobilization of toxic compounds including more mobile degradation products. For PAH-contaminated sites this cannot be assured merely by monitoring the 16 target PAHs. The combined use of a battery of biotests for different types of PAH effects such as the CALUX and the Comet assay together with bioavailability extraction methods may be a useful screening tool of bioremediation processes of PAH-contaminated soil and contribute to a more accurate risk assessment. If the bioremediation causes a release of bound PAHs that are left undegraded in an easily extracted fraction, the soil may be more toxic to organisms living in the soil as a result of the treatment. A prolonged treatment time may be one way to reduce the risk of remaining mobile PAHs. In critical cases, the remediation concept might have to be changed to ex situ remediation methods.
KeywordsAhR agonist Bioassay Bioavailability Bioremediation Natural attenuation PAH Toxicity Unintentionally produced POPs
- Bergknut M, Kucera A, Frech K, Andersson A, Engwall M, Rannug U, Koci V, Andersson PL, Haglund P, Tysklind M (2007) Identification of potentially toxic compounds in complex extracts of environmental samples using gas chromatography-mass spectrometry and multivariate data analysis. Environ Toxicol Chem 26:208–217CrossRefGoogle Scholar
- Brooks LR, Hughes TJ, Claxton LD, Austern B, Brenner R, Kremer F (1998) Bioassay-directed fractionation and chemical identification of mutagens in bioremedited soils. Environ Health Perspect 106:1435–1440Google Scholar
- Gustavsson L, Hollert H, Jonsson S, van Bavel B, Engwall M (2007) Reed beds receiving industrial sludge containing nitroaromatic compounds. Effects of outgoing water and bed material extracts in the umu-c genotoxicity assay, DR-CALUX assay and on early life stage development in zebrafish (Danio rerio). Environ Sci Pollut Res 14:202–11CrossRefGoogle Scholar
- Keiter S, Rastall A, Kosmehl T, Erdinger L, Braunbeck T, Hollert H (2006) Ecotoxicological assessment of sediment, suspended matter and water samples in the upper Danube River. A pilot study in search for the causes for the decline of fish catches. Environ Sci Pollut Res 13:308–319CrossRefGoogle Scholar
- Klee N, Gustavsson L, Kosmehl T, Engwall M, Erdinger L, Braunbeck T, Hollert H (2004) Changes in toxicity and genotoxicity of industrial sewage sludge samples containing nitro- and amino-aromatic compounds following treatment in bioreactors with different oxygen regimes. Environ Sci Pollut Res 5:313–320CrossRefGoogle Scholar
- Machala M, Vondracek J, Bláha L, Ciganek M, Neca J (2001a) Aryl hydrocarbon receptor-mediated activity of mutagenic polycyclic aromatic hydrocarbons determined using in vitro reporter gene assay. Mutat Res 497:49–62Google Scholar
- Olsman H, Hagberg J, Kalbin G, Julander A, van Bavel B, Strid Å, Tysklind M, Engwall (2005) Ah receptor agonists in UV-exposed toluene solutions of decabromodiphenyl ether (decaBDE) and in soils contaminated with polybrominated diphenyl ethers (PBDEs). Environ Sci Pollut Res 13:161–169CrossRefGoogle Scholar
- Schnurstein A, Braunbeck T (2001) Tail moment versus tail length—application of an in vitro version of the comet assay in biomonitoring for genotoxicity in native surface waters using primary hepatocytes and gill cells from Zebrafish (Danio rerio). Ecotoxicol Environ Saf 49:187–196CrossRefGoogle Scholar
- Stenlund S, Engwall M, Gitye K, Lifvergren T, Olsman H (2003) Superinduction in the DR-CALUX bioassay by extracts from soil samples taken during a soil bioremediation process. Organohalogen Compounds 60:247–250Google Scholar
- SEPA, Swedish environmental protection agency, Stockholm (1999) Metodik för inventering av förorenade områden 1999; Rapport 4918Google Scholar
- SEPA, Swedish environmental protection agency, Stockholm (2007) Lägesbeskrivning av efterbehandlingsarbetet i landet 2006; Dnr 642-737-07.Google Scholar
- TNO (1999) Monitored natural attenuation: review of existing guidelines and protocols. TNO-MEP-R 99/313. http://www.nicole.org/news/downloads/RAPPORT%2099-313%20COMPLEET+KAFT.PDF
- Villeneuve DL, Khim JS, Kannan K, Giesy JP (2002) Relative potencies of individual polycyclic aromatic hydrocarbons to induce dioxinlike and estrogenic responses in three cell lines. Wiley Periodicals, Inc., pp 28–137Google Scholar
- Vondrácek J, Svihálková-Sindlerová L, Pencíková K, Marvanová S, Krcmár P, Ciganek M, Neca J, Trosko JE, Upham B, Kozubík A, Machala M (2007) Concentrations of methylated naphtalenes, anthracenes, and phenanthrenes occurring in Czech river sediments and their effects on toxic events associated with carcinogenesis in rat liver cell lines. Environ Toxicol Chem 26:2308–2316CrossRefGoogle Scholar
- Weber R, Gaus C, Tysklind M, Johnston P, Forter M, Hollert H, Heinisch E, Holoubek I, Lloyd-Smith M, Masunaga S, Moccarelli P, Santillo D, Seike N, Symons R, Torres JPM, Verta M, Varbelow G, Vijgen J, Watson A, Costner P, Woelz J, Wycisk P, Zennegg M (2008) Dioxin- and POP-contaminated sites-contemporary and future relevance and challenges. Environ Sci Pollut Res 15:363–393CrossRefGoogle Scholar
- Wolz J, Engwall M, Maletz S, Olsman Takner H, van Bavel B, Kammann U, Klempt M, Weber R, Braunbeck T, Hollert H (2008) Changes in toxicity and Ah receptor agonist activity of suspended particulate matter during flood events at the rivers Neckar and Rhine—a mass balance approach using in vitro methods and chemical analysis. Environ Sci Pollut Res 15:536–53CrossRefGoogle Scholar