Evolution of dissolved organic matter during abiotic oxidation of coal tar—comparison with contaminated soils under natural attenuation

• Published in: Environmental science and pollution research international 2015-01, Vol.22 (2), p.1431-1443
• Main Authors: Hanser, Ogier, Biache, Coralie, Boulangé, Marine, Parant, Stéphane, Lorgeoux, Catherine, Billet, David, Michels, Raymond, Faure, Pierre
• Format: Article
• Language: English
• Subjects: air; Aquatic Pollution; Aromatic compounds; Aromatic hydrocarbons; Atmospheric Protection/Air Quality Control/Air Pollution; Attenuation; Biodegradation; Biodiversity and Ecology; Carbon; Chromatography; Chromatography, Gel; Chromatography, High Pressure Liquid; Coal; Coal tar; Coal Tar - chemistry; condensation; Condensing; Contamination; Dissolved organic matter; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental Sciences; evolution; Fluorescence; Gas chromatography; Gas Chromatography-Mass Spectrometry; gel chromatography; Genetic transformation; High-performance liquid chromatography; Humic Substances - analysis; Leachates; Leaching; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Molecular weight; Natural attenuation; Organic compounds; Organic soils; Oxidation; Oxidation-Reduction; Pollutants; polluted soils; Polycyclic aromatic hydrocarbons; Polycyclic Aromatic Hydrocarbons - analysis; Research Article; Soil contamination; Soil Pollutants - analysis; Soil pollution; Soils; Solubility; Tar; Toxicity; Waste Water Technology; Water Management; Water Pollutants, Chemical - analysis; Water pollution; Water Pollution Control; water solubility
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-014-3465-8

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.