title: Evolution of dissolved organic matter during abiotic oxidation of coal tar--comparison with contaminated soils under natural attenuation.
abstract: In former coal transformation plants (coking and gas ones), the major organic contamination of soils is coal tar, mainly composed of polycyclic aromatic compounds (PACs). Air oxidation of a fresh coal tar was chosen to simulate the abiotic natural attenuation impact on PAC-contaminated soils. Water-leaching experiments were subsequently performed on fresh and oxidized coal tars to study the influence of oxidation on dissolved organic matter (DOM) quality and quantity. The characterization of the DOM was performed using a combination of molecular and spectroscopic techniques (high-performance liquid chromatography-size-exclusion chromatography (HPLC-SEC), 3D fluorescence, and gas chromatography coupled with mass spectrometry (GC-MS)) and compared with the DOM from contaminated soils sampled on the field exposed to natural attenuation for several decades. An increase in the oxygenated polycyclic aromatic compound concentrations was observed with abiotic oxidation both in the coal tar and the associated DOM. Polycyclic aromatic hydrocarbon concentrations in the leachates exceeded pure water solubility limits, suggesting that co-solvation with other soluble organic compounds occurred. Furthermore, emission excitation matrix analysis combined with synchronous fluorescence spectra interpretation and size-exclusion chromatography suggests that oxidation induced condensation reactions which were responsible for the formation of higher-molecular weight compounds and potentially mobilized by water. Thus, the current composition of the DOM in aged soils may at least partly result from (1) a depletion in lower-molecular weight compounds of the initial contamination stock and (2) an oxidative condensation leading to the formation of a higher-molecular weight fraction. Abiotic oxidation and water leaching may therefore be a significant combination contributing to the evolution of coal tar-contaminated soils under natural attenuation.
authors.affiliation: Université de Lorraine, GeoRessources, UMR 7359, 54506, Vandœuvre-lès-Nancy, France.
authors.forename: Ogier
authors.initials: O
authors.lastname: Hanser
authors.forename: Coralie
authors.initials: C
authors.lastname: Biache
authors.forename: Marine
authors.initials: M
authors.lastname: Boulangé
authors.forename: Stéphane
authors.initials: S
authors.lastname: Parant
authors.forename: Catherine
authors.initials: C
authors.lastname: Lorgeoux
authors.forename: David
authors.initials: D
authors.lastname: Billet
authors.forename: Raymond
authors.initials: R
authors.lastname: Michels
authors.forename: Pierre
authors.initials: P
authors.lastname: Faure
mesh_terms: D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003033:Coal Tar / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006812:Humic Substances / Q000032:analysis*; D010084:Oxidation-Reduction; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis*; D012995:Solubility; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D011084:Polycyclic Aromatic Hydrocarbons; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D003033:Coal Tar