If 224 Ra is present in the water supply the alpha activity may vary depending on when the sample is analyzed. Decays through a series of short lived alpha emitting progeny, so it would have similar health consequences as 222 Rn if it were present. Radon is chemically inert and is not transported great distances from its source. EPA method 908.0 for total Uranium. Also EPA method 908.1, fluorometric.
Secondary enrichment can occur when reducing conditions cause the uranium to precipitate out.
This leads to elevated 226 Ra. Measures all alpha emitting radium isotopes.