PARTICULATE DISTRIBUTION OF PLUTONIUM AND AMERICIUM IN SURFACE WATERSFROM THE SPANISH MEDITERRANEAN COAST

Measurements of the particulate distribution of plutonium and americiu m in Spanish Mediterranean coastal waters have been carried out. Pluto nium-239,340 and Am-241 concentrations have been measured in suspended particulate matter by filtering (< 0.22 mu m) large volume (200-300 l itres) sea water samples, Results indicate that particulate plutonium constitutes on average 11 +/- 4% of the total concentration in sea wat er. In the case of americium, this percentage rises to 45 +/- 14%. Fro m the Am-241/Pu-239,Pu-240 activity ratios it is clear that suspended particulate matter is enriched in Am-241 relative to Pu-239,Pu-240 by a factor 8 +/- 4. Plutonium and americium in surface Mediterranean coa stal waters appear to be fractionated as they present a different tran sfer rate to the particles. Our measurements allowed us to estimate se diment-water distribution coefficients (K-d), which are a key paramete r to interpret differences observed between the behaviour of plutonium and americium in sea water. Distribution coefficients K-d have been e stimated to be (1.4 +/- 0.5) x 10(5) litres kg(-1) for plutonium and ( 0.9 +/- 0.5) x 10(6) litres kg(-1) for americium in surface Mediterran ean coastal waters.