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

This study reports the concentrations of important tracers of the marine environment, Po-210 and Pb-210, in different matrices from field samples collected at Central Adriatic Sea (Italy), a non-contaminated marine ecosystem. Po-210 concentration appears to decrease with increasing distance from the coast and a significant difference in Po-210 concentrations in seawater samples at two different depths is not appreciable. Po-210 and Pb-210 present the same trend in the different periods of the year. Po-210 and Pb-210 present high concentration factors and high Kd values: in particular Po-210 shows values of 2.4 10(4) in plankton, 3.2 10(5) in the particulate fraction and 1.1 10(5) in sediment; Pb-210 shows values of 1.3 10(4) in plankton, 1.8 10(4) in the particulate fraction and 4.9 10(4) in sediment. The Po-210/Pb-210 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 Po-210 in the food chain is not accompanied by an identical accumulation of Pb-210. Due to its biomagnification in the marine food chain, Po-210 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.