APPLICATION OF A GENERALIZED SCAVENGING MODEL TO TIME-SERIES TH-234 AND PARTICLE DATA OBTAINED DURING THE JGOFS NORTH-ATLANTIC BLOOM EXPERIMENT

Primary production, particle concentration and flux data, obtained as part of the JGOFS North Atlantic Bloom Experiment, have been used to construct a self consistent, time dependent, particle cycle model for the upper water column for the period 25 April-30 May 1989. Daily Th-234 concentrations and fluxes are modelled over the course of the bloom, and the results compared with available data. Use of a single pseudo-first-order rate constant k1' for the adsorption of Th-234 onto particulate material in the model gives satisfactory agreement with measured Th-234 profiles. Modelled concentrations of Th-234 on large, sinking particles-which must be known in order to calculate particle fluxes from Th-234 disequilibrium-are predicted well by the model. The results also suggest that particle fluxes determined from sediment traps may be systematically low.