Silver membranes assist in understanding oceanic primary production and short-term carbon sequestration
Sterlitech reports that silver membranes are being used by oceanographers to test for climatic changes in the open ocean.
Scientists are using the radioactive marker thorium-234 (234Th) to better understand the temporal and spatial variability of biological particle formation and sinking in the ocean.
To measure total thorium concentrations, 234Th is scavenged from a relatively small amount of ocean water using manganese dioxide.
The resulting precipitate is filtered onto the silver membrane.
Particulate 234Th (and other elements of interest, such as carbon, nitrogen, and silica) are collected via direct filtration.
The radioactivity from the thorium captured on the silver filter is then non-destructively measured using a beta counter.
"We are pleased that our 1.2micron filters are being used for this important research," stated Mark Spatz, president of Sterlitech Corporation.
"Silver membranes have many unique applications and are an especially good collection media and substrate for analysis." Silver membranes have four distinct advantages for thorium sampling:.
1 - No background radiation on silver membranes out of the box.
Compared to a glass fibre filter (GFF) or quartz filter, the silver membrane is free of 'background' radioactivity.
2 - Easily prepared for beta counting.
The 25 mm size is perfect for a standard beta counter.
3 - Silver filters are relatively dense and will partially reflect some of the radioactivity, thus resulting in higher counting efficiencies.
4 - Easy sub-sampling and precise particle collection.
Unlike GFF or quartz filters, silver membranes do not adsorb dissolved 234Th (or dissolved organic carbon or nitrogen).
Furthermore, particulate samples are stable on the membrane, such that they can be easily subsampled after 234Th analysis for other elements of interest, such as carbon, nitrogen, and silica.
For additional information on the use of Sterlitech Corporation membranes for the process of determining thorium-234 levels in the seawater, please refer to Benitez-Nelson, CR, KO Buesseler, M Rutgers van der Loeff, JE Andrews, L Ball, G Crossin, and MA Charette (2000), 'Testing a new small volume technique for determining 234Th in seawater', Journal of Radioanalytical and Nuclear Chemistry, 248 (3), 795-799 or directly to Claudia Benitez-Nelson, assistant professor, department of geological sciences, University of South Carolina.
