In topsoils, high levels of potentially toxic elements such as arsenic, may pose a problem to human health as they can be transferred through the food chain. High arsenic levels are typically found over large areas in soils developed on iron-rich parent material, such as in the soils developed on the Aubange formation (southern Wallonia, Belgian Lorraine). Anticipating the occurrence of arsenic levels in these areas affected by elevated background concentration is of interest both for improving scientific knowledge of soil geochemistry, and for soil protection management. Here we studied the geochemistry and spatial distribution of arsenic levels in the topsoils developed on an arsenic- and iron-rich parent material. To determine the factors explaining the occurrence of high arsenic content in topsoils, three spatial scales were investigated through the sampling campaign: the Aubange Formation as a whole (20 km², 51 samples), the village of Aix-sur-Cloie (intermediate scale, 5 km², 41 samples) and the plot scale (0.2 km², n=138). Analyses of major and trace elements in the collected soil samples were carried out by a portable XRF device (Niton™ XL3t GOLDD+). The majority of the samples show arsenic content that surpassed the normative value (30 mg/kg) of the Walloon soil decree (max = 170 mg/kg). Spatial trends were only observed at the formation scale and at the plot scale. At the formation scale, the trend correlates well with soil elevation, reflecting that the most weathering resistant materials are the most enriched in arsenic. No factor was found to explain the trend at the plot scale, for which the variability corresponded to the variability at the intermediate scale. Finally, exploratory factor analysis showed that arsenic and other elements (Cs, Ni, Pb, Zn and P) were associated with the presence of iron and manganese oxides.