210Po and 210Pb Concentration in Environmental Samples of the Adriatic Sea

This study reports the concentrations of important tracers of the marine environment, 210Po and 210Pb, in different matrices from field samples collected at Central Adriatic Sea (Italy), a non-contaminated marine ecosystem. 210Po concentration appears to decrease with increasing distance from the coast and a significant difference in 210Po concentrations in seawater samples at two different depths is not appreciable. 210Po and 210Pb present the same trend in the different periods of the year. 210Po and 210Pb present high concentration factors and high Kd values: in particular 210Po shows values of 2.4 104 in plankton, 3.2 105 in the particulate fraction and 1.1 105 in sediment; 210Pb shows values of 1.3 104 in plankton, 1.8 104 in the particulate fraction and 4.9 104 in sediment. The 210Po/210Pb ratio results < 1 in sea water and > 1 in the particulate fraction, sediment and plankton due to a significant fractionation occurring between the two radionuclides during their removal from solution to particle and due to their different biogeochemical cycling pathways in the marine environment. The noticeable accumulation of 210Po in the food chain is not accompanied by an identical accumulation of 210Pb. Due to its biomagnification in the marine food chain, 210Po provides the larges radiation dose to any marine organism under natural conditions. The data reported provide reference values for the Central Adriatic (Mediterranean Sea) coastal environment.