1 Abnormal trace elements concentrations in a shallow aquifer belonging to saline reclaimed environments, Codigoro (Italy) Micòl Mastrocicco 1 , Nicolò Colombani 2,# , Dario Di Giuseppe 1 , Barbara Faccini 1 , Giacomo Ferretti 1 , Massimo Coltorti 1 (1) Department of Physics and Earth Sciences, University of Ferrara, Via Saragat 1, 44122, Ferrara, Italy (2) Department of Earth Sciences, “Sapienza” University of Rome, P.le A. Moro 5, 00185, Roma, Italy # Corresponding author: e-mail: nicolo.colombani@uniroma1.it . ABSTRACT Geogenic trace elements (TE) contamination is an upcoming concern. The present study reports the temporal and spatial variation of major ions and TE in a shallow unconfined aquifer belonging to a complex marsh saline environment reclaimed in modern age and intensively cultivated. The use of intensive depth profiles in five different locations, gave insights into groundwater and sediment matrix interactions. Data indicate that the dominant factor involved in determining the spatial variability of TE is the sediment-water interaction, while the temporal variation of TE is due to the organic matter content and to the water table oscillation, which in turn drive the groundwater redox status and the mobilization of some inorganic microcostituents, such as Fe and Mn. Despite that the anthropogenic input of TEs in groundwater from fertilizers sources cannot be undoubtedly ruled out, given the elevated TEs background concentrations; the combined use of high-resolution sediment profiles, seasonal groundwater sampling and end-member analyses is a promising procedure to distinguish between anthropogenic metal contamination and geogenic contribution in reclaimed deltaic environments. Finally, this study underlines the need of having a dense piezometer network and to perform several monitoring campaigns to ensure that the temporal and spatial variability could be correctly represented and background values of TE could be confidently determined. Keywords: agricultural soils, concentration profiles, vadose zone, metals contamination, reclaimed environments.