Uptake and depuration of I 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.