Uptake and depuration of 131I by the macroalgae Catenella nipae – Potential use as an environmental monitor for radiopharmaceutical waste

A study was initiated to establish the suitability of the macroalgae, Catenella nipae as an environmental surveillance monitor for radiopharmaceutical waste discharges to aquatic environments. A series of experiments were conducted to establish the radioactive iodine (131I) concentration factor, and uptake and depuration characteristics of C. nipae. The steady state concentration factor was estimated to be 630 ± 80 mL g−1, with an uptake half-time of 160 ± 20 min. Elimination of 131I was found to follow a two phase model, the first having a rapid elimination rate with a half-time of <1 min, followed by the second phase with a half-time of 3.2 days. Application of the Michaelis–Menton model allowed calculation of an estimate for activity concentration of 131I in environmental waters from C. nipae sampling devices in the Brisbane River estuary, Australia. The results suggest that C. nipae may be used as an environmental radioactive waste sentinel.