Po-210 in plankton and fish from coastal waters (gulf of Trieste, northern Adriatic Sea)

The activity concentrations of Po-210 were determined in seawater (<0.45 <mu>m), suspended particulate matter (0.45-20 mu m), fractionated plankton (20-50 mu m, 50-200 mu m, >200 mu m) and tissues from four fish species, namely European seabass (Dicentrarchus labrax), Golden grey mullet (Chelon auratus), Gilt-head bream (Sparus aurata) and Common pandora (Pagellus erythrinus), collected in the Gulf of Trieste (northern Adriatic Sea). The activity concentration of Po-210 in seawater varied from 0.4 to 2.2 mBq/L in the dissolved phase (<0.45 <mu>m) and from 0.4 to 0.8 Bq/L in suspended particulate matter (0.45-20 mu m). Plankton fractionation showed the levels of 62-395 Bq/kg Po-210 in the >200 mu m mesoplankton fraction, 65-459 Bq/kg in 50-200 mu m and 52-537 Bq/kg in 20-50 mu m microplankton fractions. No significant differences were found between fractions. The Po-210 distribution trend in fish tissues was in order: liver > stomach with intestine > kidney > spleen > gonads > gills > muscle. Bioaccumulation factors were determined for fish tissues indicating that the amount of Po-210 mostly depends on fish feeding habits. Hence, the main pathway entry of Po-210 is through ingested food. The highest estimated average total annual effective ingestion doses of Po-210 are obtained via the consumption of Common Pandora (7.1 mu Sv/year to 16.5 mu Sv/year) while the lowest doses are due to the consumption of European seabass (0.32 mu Sv/year to 0.76 mu Sv/year). Comparison with levels reported for other Mediterranean and Atlantic areas showed that only activitiy concentrations of Po-210 in fish appear significantly different, most likely because different fish species were analysed. The human dose exposure via fish consumption in the area is rather low.