contaminated site observatory Rontok Lake Paul Schofield Rontok Lake is a contaminated site in the Upper Silesian coal basin, Poland, where radium-bearing waters discharged from coal mines have led to elevated radioactivity concentrations in the water, sediments and surrounding environment. It forms part of the ALLIANCE NORM observatory network and offers a unique field laboratory for studying natural radionuclide transport, accumulation and ecological effects in a freshwater system affected by mining activity. Access requires authorisation via SCRS-GIG based on mutual agreement with the site owner. Located at Silesian Centre for Environmental Radioactivity, Central Mining Institute (SCRS-GIG). Chałupnik et al., Journal of Environmental Radioactivity Vol. 54, s. 85-98 (2001) http://www.gig.eu