Changes in HTO and OBT activity concentrations in the Perch Lake aquatic ecosystem

Perch Lake, a small, shallow shield lake located on the site of Chalk River Laboratories (CRL), contains elevated levels of tritium due to leakage from a nearby nuclear waste management area. The releases have been going on for many years and tritium concentrations in Perch Lake have decreased since the year 2000. Lake water, sediments, aquatic plants, clams and fish were collected during the summer and fall of 2003 and 2013 at three locations in the lake. HTO concentrations were measured in all samples and OBT concentrations were measured in sediments, plants, clams and fish. HTO concentrations in lake water were roughly uniform in time and space, except close to the shoreline where concentrations were elevated by higher tritium levels in streams entering the lake. HTO concentrations of biota were similar to concentrations in lake water at the site where they were collected. OBT concentrations in biota showed little variation in time or space in 2013 but OBT concentrations in aquatic plants and sediments showed much greater variability in 2003. (author)