Determination of cosmogenic ^32P and ^33P in environmental samples

Understanding phosphorus dynamics in marine environment is of great importance, and appropriate trac- ers for phosphorus cycling in oceans are invaluable. In this study, two methods were developed for extrac- tion, purification, and determination of naturally occurring ^32p and ^33P in rainwater, marine plankton and sediments using both a low-level beta counter （LBC） and an ultra-low-level liquid scintillation spectrome- ter （LSS）. Blanks, chemical yields and counting efficiencies were quantified for both methods. The chemical purification of ^32P and ^33P separated by both procedures was validated by their decay curves. The absorber thickness of aluminum for LBC was assessed as 39.2 mg/cm2. ^32P and ^33P specific activities in some rain samples were determined by both methods and showed good consistent results. The advantage of the LSS over the LBC is apparent in its high counting efficiency and in determining samples with high concentration of stable phosphorus. However, when measuring environmental samples with low concentration of stable phosphorus, such as rainwater, both methods can be used and each has its distinct advantage.