title: Impacts of one century of wastewater discharge on soil transformation through ferrolysis and related metal pollutant distributions.
abstract: Discharge of wastewater leading to notable soil surface contamination is widely reported. But few works highlight the fast dynamics of soils and their morphological transformations that may result from such anthropogenic activities. Near Paris (France), sandy Luvisols were irrigated with urban wastewater since the 1890s. Within and outside the discharge area, the soil cover presents decameter-sized cryogenic structures. We studied macro morphological soil characteristics, soil chemistry and clay mineralogy on selected bulk samples, as well as contemporary pedofeatures and related metal pollutant distribution patterns in soil thin sections from subsurface horizons. Annual repetitive waterlogging and drying cycles initiated a hydromorphic soil forming process: ferrolysis, based on iron reduction producing alkalinity under anaerobic conditions, and iron oxidation producing acidity in aerobic conditions. Its intensity was enhanced at the top of thick clay-rich B-horizons in the center of cryogenic structures. The polygonal soil structure favored the evacuating of soil water and alkalinity. Within one century, such recurrent alternating redox conditions have led to clay destruction, removal of iron, strong bleaching of the E horizon and formation of abiotic Fe-rich pedofeatures at depth. In addition, between anaerobic clay-rich B and aerated E or C horizons, the contrasting hydrodynamic conditions enhanced manganese (Mn) oxidizing fungal activity and the formation of biotic Mn-rich pedofeatures. Both types of pedofeatures trapped metal pollutants in deep soil horizons. In our work, the impacts of centenary anthropogenic activity were amplified by millenary cryogenic structures, acting together to promote fast soil dynamics, within a few decades.
authors.affiliation: INRA-Agro-ParisTech, UMR 1402 Ecosys, pôle Ecotoxicologie, RD10, 78026, Versailles Cedex, France. Electronic address: folkert.van-oort@inra.fr.
authors.forename: Folkert
authors.initials: F
authors.lastname: van Oort
authors.affiliation: MINES ParisTech, PSL Research University, Géosciences, 35, rue St Honoré, 77305 Fontainebleau, France.
authors.forename: Médard
authors.initials: M
authors.lastname: Thiry
authors.affiliation: CEA-CNRS, UMR 3685 NIMBE/LAPA, 91191 Gif-sur-Yvette Cedex, France.
authors.forename: Eddy
authors.initials: E
authors.lastname: Foy
authors.affiliation: INRA-Agro-ParisTech, UMR 1402 Ecosys, pôle Ecotoxicologie, RD10, 78026, Versailles Cedex, France.
authors.forename: Kenji
authors.initials: K
authors.lastname: Fujisaki
authors.affiliation: INRA-Agro-ParisTech, UMR 1402 Ecosys, pôle Ecotoxicologie, RD10, 78026, Versailles Cedex, France.
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Delarue
authors.affiliation: INRA-Agro-ParisTech, UMR 1402 Ecosys, pôle Ecotoxicologie, RD10, 78026, Versailles Cedex, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Dairon
authors.affiliation: WUR, Landscape Centre, PO Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: Toine
authors.initials: T
authors.lastname: Jongmans
keywords: Ferrolysis; Fungal activity; Microscale trace metal accumulations; Pedofeatures; Polygonal soils; Wastewater discharge