Volatility of 125I in fresh water

To define the rate of 129I transfer from aquatic to terrestrial ecosystems, in support of the Canadian Nuclear Fuel Waste Management Program, we measured rates of 125I and 14C loss from glass flasks. Measured 125I loss rates were less than 0.5% of the 14C loss rate, and water-air partition coefficients for 125I were 7.2 × 104 litre air litre−1 water or greater. Gaseous loss of 125I was slower from river water than from distilled water, and still slower in the presence of algae, or from sediment slurries under oxic or low-oxic conditions. No 125I loss was detectable under methanogenic conditions. Sediment slurries in contact with 125I were used to measure water-sediment partition coefficients (KD) under oxic (KD = 70–187 litre kg−1) and low-oxic (KD = 25–42 litre kg−1) conditions. From this study we conclude that the first-order gaseous evasion rate from fresh water to the atmosphere for 129I is < 1.9 × 10−3 a−1, and that the water-to-sediment transfer rate is between 1.0 and 3.4 a−1.