[en] Upland peat soils are generally regarded as effective sinks of atmospherically deposited lead. However, the physical process of erosion has the potential to transform peat soils from sinks to sources of lead contamination. Lead input and fluvial lead outputs (dissolved + particulate) were estimated for a contaminated and severely eroding peatland catchment in the southern Pennines, UK. Lead input to the catchment is 30.0 ± 6.0 g ha^-1 a^-1 and the output from the catchment is 317 ± 22.4 g ha^-1 a^-1. Suspended particulate matter accounts for 85% of lead export. Contaminated peat soils of the catchment are a significant source of lead to the fluvial system. This study has demonstrated strong coupling between the physical process of erosion and the mobilization of lead into the fluvial system. The process of peat erosion should therefore be considered when estimating lead outputs from peatland catchments, especially in the context of climate change. - Erosion can transform peat soils from sinks to sources of lead contamination