Active reclamation is often necessary to ensure a transformation of mining waste into Technosols-"soils dominated or strongly influenced by human-made material"and restore its utility and environmental value. The objective of this study is to assess the spatial variation of the physicochemical properties relevant for reclamation and Technosol formation on dredged-sediment landfills left by alluvial gold mining in a chronosequence of reclamation (0, 4, 8, and 12 years). We hypothesize a higher spatial dependency of most soil properties with increasing time of Technosol formation and an overall homogenization of the soil resulting from pedogenetic processes. Our results show early signs of Technosol pedogenesis with strong physicochemical changes after only few years of formation. We observed that older Technosols (>4 years) are more acidic, have less nutrient and organic matter content, higher exchangeable cations, and less signs of compaction than nonrevegetated landfills.The content of organic matter, phosphorus, and exchangeable cations show the highest spatial variability in Technosols of all ages. In older Technosols, most soil properties showed less spatial variability than in younger Technosols. A multivariate geostatistical approach allowed the delineation of zones with distinctive physicochemical properties within areas of the chronosequence. The results show that reclamation and Technosol formation lead to spatially dependent fragmentation processes reflected in more and smaller clustered zones in Technosols after 12 years of formation. From the perspective of reclamation management, understanding the spatial variability of highly heterogeneous Technosols where substantial changes can be observed within small distances can support the development of site-specific reclamation strategies suitable to the characteristics of each field as well as the determination of its potential uses.

Active reclamation is often necessary to ensure a transformation of mining waste into Technosols -“soils dominated or strongly influenced by human made material” - and restore its utility and environmental value. The objective of this study was to assess the spatial variation of the physicochemical properties of a Technosol forming on dredged sediment landfills left by alluvial gold mining in a chronosequence of reclamation (0, 4, 8 and 12 years). We hypothesized a higher spatial dependency of most soil properties with increasing time of Technosol formation and an overall homogenization of the soil resulting from pedogenetic processes. Our results showed that most of the investigated physical and chemical properties changed significantly among Technosols of different ages. The content of organic matter, phosphorus, and exchangeable cations showed the highest spatial variability in Technosols of all ages. In older Technosols, most soil properties showed less spatial variability than in younger Technosols. A multivariate geostatistical assessment allowed the delineation of spatial clusters i.e. homogeneous zones with distinctive physicochemical properties within areas of the chronosequence. This spatial clustering showed that reclamation and Technosol formation led to spatially-dependent fragmentation processes reflected in more and smaller homogeneous zones in the oldest Technosol assessed in the chronosequence. From the perspective of reclamation management, understanding the spatial variability of highly heterogeneous Technosols where substantial changes can be observed within small distances can support the development of reclamation strategies suitable to the characteristics of each field as well as the determination of its potential uses.