A technique to determine concentrations of 32P, 33P and 7Be in dissolved and particulate forms, in the upper ocean was developed. By using a large volume in situ filtration and concentration
system (LV-FiCS), several tons of seawater at different depths were filtered concurrently through two kinds of filters. The
dissolved radionuclides were concentrated onto adsorbents in the LV-FiCS. The radionuclides obtained were further purified
by precipitation and ion-exchange chromatography, and quantified by gamma-spectrometry and ultra-low level liquid scintillation
counter measurements. The technique was used with good results in a coastal area of Ibaraki, Japan.