Preliminary estimation of 210Po and 210Pb flux during autumn in coastal waters off Monaco using sediment trap measurement

Full text: The particle reactive nuclides, 210Po and 210Pb are generally used for the estimation of particle residence times in coastal and oceanic waters. During autumn 1995, we analyzed these radionuclides in the surface water and settling particles collected off Monaco to estimate the particle flux in this coastal system. The sediment trap was moored 3 km south of the Port of Monaco at a water depth of 150 m and the duration of sampling was approximately 1 month. Surface water samples (30 l) were collected monthly and filtered through 0.45 μm Nucleopore filters. 210Po and 210Pb were measured in both the surface water (particulate form, dissolved form) and the settling particles. By using box-model calculation, our preliminary estimates of residence times suggest that 210Po in surface water off Monaco is recycled during autumn, while the residence times of 210Pb were between 0.16 and 0.55 year. The mass flux of settling particles obtained during autumn 1995 ranged between 0.23 and 1.2 g/m2/day. These values are comparable with previously reported fluxes for the same coastal area during the fall. Corresponding 210Po and 210Pb fluxes were 0.12 - 0.96 and 0.05 - 0.20 Bq/m2/day, respectively