Change search
ReferencesLink to record
Permanent link

Direct link
Comparison of Fenton's Reagent and Ozone Oxidation of Polycyclic Aromatic Hydrocarbons in Aged Contaminated Soils
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
Show others and affiliations
2006 (English)In: Journal of Soils and Sediments, ISSN 1614-7480 (Online), Vol. 6, no 4, 208-214 p.Article in journal (Refereed) Published
Abstract [en]

Background, Aim and Scope: Polycyclic aromatic hydrocarbons (PAHs) are formed as a result of incomplete combustion and are among the most frequently occurring contaminants in soils and sediments. PAHs are of great environmental concern due to their ubiquitous nature and toxicological properties. Consequently, extensive research has been conducted into the development of methods to remediate soils contaminated with PAHs. Fenton's reagent or ozone is the most commonly studied chemical oxidation methods. However, the majority of remediation studies use soils that have been artificially contaminated with either one or a limited number of PAH compounds in the laboratory. Hence, it is essential to extend such studies to soils contaminated with multiple PAHs under field conditions.

Objectives. The objective of this study is to investigate the capacity of Fenton's reagent and ozone to degrade PAHs in soils. The soils have been collected from a number of different industrial sites and, therefore, will have been exposed to different PAH compounds in varying concentrations over a range of time periods. The capacity of Fenton's reagent and ozone to degrade PAHs in industrially contaminated soils is compared to results obtained in studies using soils artificially contaminated with PAHs in the laboratory.

Materials and Methods: Nine soil samples, contaminated with PAHs, were collected from five different industrial sites in Sweden. For the Fenton's reagent procedure, the pH of the soil slurry samples was adjusted to pH 3 and they were kept at a constant temperature of 70ºC whilst H2O2 was added. For the ozone procedure, soil samples were mixed with 50% water and 50% ethanol and kept at a constant temperature of 45 ºC. Ozone was then continually introduced to each soil sample over a period of four hours. Following the Fenton's reagent and ozone oxidation procedures, the samples were filtered to isolate the solid phase, which was then extracted using pressurized liquid extraction (PLE). The sample extracts were cleaned up using open columns and then analysed by gas chromatography-mass spectrometry (GC-MS).

Results: The relative abundance of the detected PAHs varied between soils, associated with different industries. For example, low molecular weight (LMW) PAHs were more abundant in soil samples collected from wood impregnation sites and high overall PAH degradation efficiencies were observed in soils originating from these sites. In the contaminated soils studied, PAHs were more effectively degraded using Fenton's reagent (PAH degradation efficiency of 40-86%) as opposed to ozone (PAH degradation efficiency of 10-70%). LMW PAHs were more efficiently degraded, using ozone as the oxidizing agent, whereas the use of Fenton's reagent resulted in a more even degradation pattern for PAHs with two through six fused aromatic rings.

Discussion: The degradation efficiency for both methods was largely dependent on the initial PAH concentration in the soil sample, with higher degradation observed in highly polluted soils. LMW PAHs are more susceptible to degradation than high molecular weight (HMW) PAHs. As a result of this the relative abundance of large (often carcinogenic) PAHs increased after chemical oxidation treatment, particularly after ozone treatment. Repeated Fenton's reagent treatment did not result in any further degradation of soil PAHs, indicating that residual soil PAHs are strongly sorbed. The effectiveness of the two oxidation treatment approaches differed between industrial sites, thus highlighting the importance of further research into the influence of soil properties on the sorption capacity of PAHs.

Conclusions: This study demonstrates that the degree to which chemical oxidation techniques can degrade soil bound PAHs chemical degradation is highly dependent on both the concentration of PAHs in the soils and the compounds present, i.e. the various PAH profiles. Therefore, similarities in the PAH degradation efficiencies in the nine soil samples studied were observed with the two chemical oxidation methods used. However, the degradation performance of Fenton's reagent and ozone differed between the two methods. Overall, Fenton's reagent achieved the highest total PAH degradation due to stronger oxidation conditions. LMW PAHs showed higher susceptibility to oxidation, whereas high molecular weight (HMW) PAHs appear to be strongly sorbed to the soils and therefore less chemically available for oxidation. This study highlights the importance of including soils collected from a range of contaminated sites in remediation studies. Such soil samples will contain PAH contaminants of varying concentrations, chemical and physical properties, and have been aged under field conditions. In addition to the chemical and physical properties of the soils, these factors will all influence the chemical availability of PAHs to oxidation.

Recommendations and Perspectives: We recommend including aged contaminated soils in chemical degradation studies. In future chemical remediation work, we intend to investigate the potential influence of the chemical and physical properties of PAHs and soil parameters potential influence on the chemical oxidation efficiency in aged contaminated soils.

Due to the vast number of contaminated sites there is a great need of efficient remediation methods throughout the world. This study shows the difficulties which may be experienced when applying remediation methods to a variation of contaminated sites.

Place, publisher, year, edition, pages
Berlin: Springer , 2006. Vol. 6, no 4, 208-214 p.
Keyword [en]
aged contaminated soils, chemical oxidation, coke production, degradation, Fenton's reaction, gas works, ozone oxidation, polycyclic aromatic hydrocarbons (PAHs), soil remediation, wood impregnation
URN: urn:nbn:se:umu:diva-12414DOI: 10.1065/jss2006.08.179OAI: diva2:152085
Available from: 2007-08-13 Created: 2007-08-13Bibliographically approved
In thesis
1. The influence of soil and contaminant properties on the efficiency of physical and chemical soil remediation methods
Open this publication in new window or tab >>The influence of soil and contaminant properties on the efficiency of physical and chemical soil remediation methods
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 A vast number of sites that have been contaminated by industrial activities have been identified worldwide. Many such sites now pose serious risks to humans and the environment. Given the large number of contaminated sites there is a great need for efficient, cost-effective  remediation methods. Extensive research has therefore been focused on the development of such methods. However, the remediation of old industrial sites is challenging, for several reasons.

One major  problem is that organic contaminants become increasingly strongly sequestered as they persist in the soil matrix for a long period of time. This process is often referred to as ‘aging’, and leads to decreasing availability of the contaminants, which also affects the remediation efficiency. In the work underlying this thesis, the influence of soil and contaminant properties on the efficiency of various physical and chemical soil remediation methods was investigated. The investigated contaminants were polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs).

Briefly, the results show that as the size of soil particles decreases the contaminants become more strongly sorbed to the soil’s matrix, probably due to the accompanying increases in specific surface area. This affected the efficiency of the removal of organic pollutants by both a process based on solvent washing and processes based on chemical oxidation. The sorption strength is also affected by the hydrophobicity of the contaminants. However, for a number of the investigated PAHs their chemical reactivity was found to be of greater importance for the degradation efficiency. Further, the organic content of a soil is often regarded as the most important soil parameter for adsorption of hydrophobic compounds. In these studies the effect of this parameter was found to be particularly pronounced for the oxidation of low molecular weight PAHs, but larger PAHs were strongly adsorbed even at low levels of organic matter. However, for these PAHs the degradation efficiency was positively correlated to the amount of degraded organic matter, probably due to the organic matter being oxidized to smaller and less hydrophobic forms. The amount of organic matter in the soil had little effect on the removal efficiency obtained by the solvent-washing process. However, it had strong influence on the performance of a subsequent, granular activated carbon-based post-treatment of the washing liquid.

In conclusion, the results in this thesis show that remediation of contaminated soils is a complex process, the efficiency of which will be affected by the soil matrix as well as the properties of the contaminants present at the site. However, by acquiring thorough knowledge of the parameters affecting the treatability of a soil it is possible to select appropriate remediation methods, and optimize them in terms of both remediation efficiency and costs for site- and contaminant-specific applications.

76 p.
Fenton’s reagent, ozone, solvent washing, granular activated carbon, GAC
National Category
Environmental Sciences
Research subject
urn:nbn:se:umu:diva-21040 (URN)978-91-7264-763-3 (ISBN)
Public defence
2009-04-24, KB3B1, KBC-huset, Umeå Universitet, 901 87 Umeå, 13:00 (English)
Available from: 2009-04-03 Created: 2009-04-01 Last updated: 2009-04-03Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Jonsson, SofiaPersson, YlvaHaglund, PeterTysklind, Mats
By organisation

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 316 hits
ReferencesLink to record
Permanent link

Direct link