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Degradation and formation of polycyclic aromatic compounds during bioslurry treatment of an aged gasworks soil
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
2003 (English)In: Environmental Toxicology and Chemistry, ISSN 0730-7268, Vol. 22, no 7, 1413-1420 p.Article in journal (Refereed) Published
Abstract [en]

The goals of this study were to investigate the relative degradation rates of polycyclic aromatic compounds (PACs) in contaminated soil, and to assess whether persistent oxidation products are formed during their degradation. Samples were taken on five occasions during a pilot-scale bioslurry treatment of soil from a former gasworks site. More than 100 PACs were identified in the soil, including unsubstituted polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs), heterocyclic PACs, and oxygenated PAHs (oxy-PAHs), such as ketones, quinones, and coumarins. During the treatment, the low molecular weight PAHs and heterocyclics were degraded faster than the high molecular weight compounds. The unsubstituted PAHs also appear to have degraded more quickly than the corresponding alkyl-PAHs and nitrogen-containing heterocyclics. No new oxidation products that were not present in the untreated soil were identified after the soil treatment. However, oxy-PAHs that were present in the untreated soil were generally degraded more slowly than the parent compounds, suggesting that they were formed during the treatment or that they are more persistent. Two oxidation products, 1-acenaphthenone and 4-oxapyrene5-one, were found at significantly higher concentrations at the end of the study. Because oxy-PAHs can be acutely toxic, mutagenic, or carcinogenic, we suggest that this group of compounds should also be monitored during the treatment of PAH-contaminated soil.

Place, publisher, year, edition, pages
2003. Vol. 22, no 7, 1413-1420 p.
Keyword [en]
polycyclic aromatic hydrocarbons, degradation, oxygenated polycyclic aromatic hydrocarbons formation, soil
URN: urn:nbn:se:umu:diva-9229DOI: doi:10.1897/1551-5028(2003)22<1413:DAFOPA>2.0.CO;2PubMedID: 12836964OAI: diva2:148900
Available from: 2008-05-23 Created: 2008-05-23 Last updated: 2009-12-07Bibliographically approved
In thesis
1. Analysis of PAHs and their transformations products in contaminated soil and remedial processes
Open this publication in new window or tab >>Analysis of PAHs and their transformations products in contaminated soil and remedial processes
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soil that is heavily contaminated with polycyclic aromatic hydrocarbons (PAHs) is often found at the sites of former gasworks and wood-impregnation plants. Since PAHs are toxic these sites represent a hazard to human health and the environment, and therefore they need to be treated, preferably by a method that destroys the contaminants, and thus eliminates the problem permanently. However, during biological and chemical degradation of PAHs other toxic compounds may be formed. If these transformation products are sufficiently persistent they could potentially accumulate during remedial processes.

In the work underlying this thesis the degradation and transformation of PAHs were studied in three remedial processes: viz. a pilot-scale bioslurry reactor, microcosms with wood-rotting fungi and lab-scale treatments with Fenton's reagent. A group of transformation products referred to as oxygenated-PAHs (oxy-PAHs) was found to be particularly important, as these compounds are toxic and were shown to be relatively persistent in the environment. The oxy- PAHs were, for instance, found at significant concentrations in the gasworks soil used in most of the studies. This soil was highly weathered and had therefore been depleted of the more readily degradable compounds. In addition, experiments in which earthworms were exposed to the gasworks soil showed that the oxy-PAHs were more easily taken up in living organisms than PAHs.

To facilitate the studies, new extraction and fractionation methods were developed. For instance, pressurized liquid extraction (PLE) was investigated for its reliability and efficiency to extract PAHs and oxy-PAHs from soil. Furthermore, a selective PLE-method was developed that can simultaneously extract and separate the PAHs and oxy-PAHs into two different fractions. This was accomplished by adding a chromatographic material (silica or Florisil) to the extraction cell.

Under certain conditions all three remedial processes resulted in increasing amounts of oxy- PAHs in the soil. For example, 1-acenaphthenone and 4-oxapyrene-5-one accumulated in the bioslurry reactor. Similarly, in the soil inoculated with a white-rot fungus 9-fluorenone, benzo[a]anthracene-7,12-dione, 4-hydroxy-9-fluorenone and 4-oxapyrene-5-one accumulated. Finally, in an ethanol-Fenton treatment the concentration of some PAH-quinones increased in the soil.

The results show that it might be necessary to monitor oxy-PAHs as well as PAHs during the remediation of PAH-contaminated sites. Otherwise, the soil may be considered detoxified too early in the process. In the long term it would be desirable to include analyses with sufficient marker compounds to follow the possible production and elimination of the oxy-PAHs. However, until such compounds can be identified it is suggested that contaminated soil should be screened for oxy-PAHs in general. The selective PLE-method presented in this thesis could be a useful tool for this.

Place, publisher, year, edition, pages
Umeå: Kemi, 2003. 43 p.
Environmental chemistry, polycyclic aromatic hydrocarbons, PAHs, degredation, transformation, formation, accumulation, oxidation products, metabolites, oxogenated polycyclic aromatic hydrocarbons, oxy-PAHs, soil, gasworks, remediation, bioremediation, bioslurry, wood-rotting fungi, Fenton´s reagent, avaliability, bioavaliability, chemical analysis, extraction, pressurized liquid extraction, PLE, accelerated solvent extraction, ASE, Miljökemi
National Category
Environmental Sciences
Research subject
Analytical Chemistry
urn:nbn:se:umu:diva-57 (URN)91-7305-452-6 (ISBN)
Public defence
2003-05-24, Umeå, 10:00 (English)
Available from: 2003-05-24 Created: 2003-05-24 Last updated: 2009-12-07Bibliographically approved

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