Climatic influence on mobility of organic pollutants in Technosols from contrasted industrial activities
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Understanding long-term effects of climate on soil with organic contaminations is a major advantage for natural attenuation assessment. However, studies are often limited to evaluating the evolution of availability of one/several selected contaminant(s) spiked into natural or agricultural soils. These approaches are not representative of real cases of industrial wastelands. In this study, we want to understand the evolution of a broad set of anthropogenic soil and especially the organic matter reactivity through climate aging factors.
Materials and methods
Eleven soils were sampled from representative former industrial sites contaminated with polycyclic aromatic hydrocarbons (PAHs) (coking and gas plants, backfills). They were broadly characterized and then aged through several experimental climatic simulations in controlled conditions: freeze-thaw cycles (FTCs), wetting-drying cycles (WDCs), and heating on dry and wet soil (HDS and HWS). The variation of dissolved organic carbon (DOC) content was used as an indicator of the modification of the organic matter reactivity induced by climate aging modalities.
Results and discussion
Physico-chemical soil characterization indicates similar characteristics to those of Technosols but very different compared to natural/agricultural soils. A principal component analysis (PCA) showed a clear correlation between initial DOC, PAH concentration, and the solvent extractible fraction of organic matter. This means that DOC is a clear indicator of technogenic organic matter mobility. After aging, DOC followed several significant trends depending on the aging modality. These trends were controlled by the competition of (i) biodegradation/oxidation, (ii) formation/disruption of aggregates, and (iii) sorption/desorption processes. A multivariate analysis performed by PCA revealed that DOC variations were strongly linked with the silt fraction and the occurrence of vegetation cover after FTC, HWS, and HDS. These parameters emphasized their important role as regulating the reactivity of organic compounds during climate aging.
This study provides the first steps to assess natural evolution and natural attenuation of organic pollutants in historically contaminated soils. This original approach reveals the influence of climate aging on the reactivity of technogenic organic matter. Moreover, this influence appears to be particularly intensified in soil with a high silt fraction and the occurrence of vegetation cover.
KeywordsAging DOC PAH Technogenic organic matter Technosols
We would like to thank the French Environmental Agency (Ademe; Hélène Roussel) and the French Geological and Mining Research Institute (BRGM; Céline Blanc and Philippe Bataillard) for their financial support and advices through this work. We also wish to thank the French Industrial Wasteland Scientific Interest Group (Gisfi; Noële Raoult, Mélanie Malacarne, Lucas Charrois, and Rémi Baldo) for their technical help and providing us samples of the studied materials. The authors wish to thank Adeline Bouchard (LSE), Delphine Catteloin (Georessources), Alain Rakoto (LSE), and Frédéric Rees (LSE) for helpful discussions and technical support.
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