Recent thinking about ocean scavenging models has led to different interpretations of essentially the same data set. On the one hand correlations between the Th removal rate constant and new productivity suggest that biological processes are responsible for removal of metals from solution. On the other hand many anomalous variations in scavenging variables can be explained by a Brownian-pumping model that suggests that adsorption by colloids and their subsequent coagulation is the main process. Field studies will be conducted to learn more about these two very different mechanistic pathways and distinguish between them. Work will be coordinated with Dr. Chih-An Huh (OSU) to obtain Isotope Dilution Mass Spectrometry analyses of Th-230 and Th-232. New techniques will enable us to use smaller samples for Th analyses. The use of hollow- fiber cross-flow filtration techniques will determine how much dissolved Th is present as a colloidal phase. Recycling rate of Th-234 relative to C, N, Pb-210, Po-210, total suspended matter and colloid distributions will be studied in the Monterey Bay/California Current region.
