Biotic, temporal and spatial variability of tritium concentrations in transpirate samples collected in the vicinity of a near-surface low-level nuclear waste disposal site and nearby research reactor

► Data on environmental tritium behaviour over 21 months related to a legacy waste site are presented. ► The relative contributions of atmospheric and groundwater exposure pathways from multiple sources are elucidated. ► Patterns of measured tritium concentrations in plant transpirate, over time and space, are described and explained in terms of source terms and environmental variables.