Investigation of chemical remediation techniques for polycyclic aromatic compounds contaminated soil by high resolution mass spectrometry

The functionality of soil – as a part of the ecosystem – is extremely essential for the existence of life and environment. Therefore, concerns about the permanent inorganic and organic pollution of the soil have dramatically increased in the last few years. The substance class of polycyclic aromatic hydrocarbons (PAHs) plays a significant role as a contaminant since they exhibit high carcinogenic and toxic potential. Further use of these contaminated soils is hardly or not at all possible and therefore must undergo decontamination, which turns out to be very challenging. The complexity of soil, as an environmental medium, coupled with the presence of thousands of unknown pollutants complicates the identification of the relevant chemical and physical parameters for remediation. The aim of this work was to establish chemical processes for the oxidation of high molecular weight PAHs, which are relatively insoluble in water due to higher number of aromatic rings, in order to enhance the microbial remediation of these compounds. Various oxidation techniques, like the Fenton reaction, ozonolysis and photooxidation, were applied to a highly contaminated soil and the obtained products were analyzed using ultrahigh resolution mass spectrometry (UHRMS). This analytical method facilitates a comprehensive characterization of various oxidized and non-oxidized compounds and a detailed understanding of the chemical reaction on a molecular level. A key result of this work revealed that no significant degradation of high molecular weight PAHs was observed in chemical treatments using water as sole solvent. Therefore, the addition of a co-solvent was necessary to increase the availability of high molecular weight PAHs for chemical remediation. The addition of 5% v/v toluene as a co-solvent significantly improved the degradation of PAHs in Fenton reaction and ozonolysis by promoting the formation of highly oxidized hydrocarbons.