Abstract: After the analysis and comparison of the four methods (precipitate, direct absorption, benzene synthesis and AMS) used in determining radiocarbon, bubbling and direct absorption methods were adopted to measure ¹⁴C environmental water. 50 L water was put into flask, then H₃PO₄ was added, and the DIC in water sample was dissolved to form CO₂ by nitrogen bubbling. Released CO₂ is trapped in a sodium hydroxide molar solution before being precipitated as calcium carbonate. Calcium carbonate from water is acidified to release CO₂. CO₂ is absorbed by Carb-sorb E measured by LSC. The recovery was proven to be 90.3% and the limit detection is 0.2 mBq/L.This method was used to analyze different water samples of Fujian province results of radiocarbon activity concentrations of which are between 1.31—10.26 mBq/L.

Key words: radiocarbon, environmental water, inorganic carbon, direct absorption method