This document specifies the method and the conditions for the determination of ²³²Th activity concentration in samples of environmental water (including sea waters) and waste waters before release to the environment using alpha spectrometry and ²²⁹Th as a recovery tracer. A chemical separation allows to separate and purify thorium from a test portion of the sample.

The general principles outlined in this document can be applied for the analysis of other alpha-emitting thorium isotopes such as ²²⁸Th and ²³⁰Th in aqueous samples.