Particle Scavenging in the Upper Water Column off Mindoro Island, Philippine:234Th/238U Disequilibria

Vertical profiles of dissolved and particulate234Th in the upper water column of four stations in the narrow channel adjacent to Mindoro Island, Philippine were determined during November 1991. Calculated from the degree of disequilibrium between particle-reactive234Th and soluble parent,238U, the residence times of dissolved and particulate234Th range from 20 to 42 days and from 9 to 17 days, respectively. Vertical234Th fluxes of 4300–7000 dpm m−2day−1from the upper 200 m are required to balance the deficiency of234Th.