Presence of U,Np and Pu in shells from the coast of the south of China.

This study reports first results on uranium (U), neptunium (Np) and plutonium (Pu and Pu) isotopes in shell samples (i.e. oyster, clam and scallop shells) from the coast of the South of China. The Pu/Pu and U/U atom ratios are used for source identification, and the Np/Pu, Np/U and U/Pu non-isotopic atom ratios to study the relative bioaccumulation of Np, Pu and U during the shell formation. The obtained concentration levels are in the 10-10 atoms g range in every case. Clear regional differences are observed in the case of the Pu/Pu atom ratio, with average values lower along the coast of East China Sea (average 0.227 ± 0.120, n = 5) compared to the South China Sea (average 0.258 ± 0.018, n = 7), showing a possible influence of the Pu released at the Pacific Proving Ground nuclear test site. U/U ( × 10) atom ratios range from 0.046 ± 0.009 to 0.524 ± 0.135, in agreement with the expected levels in surface seawater from the China Sea. Np/Pu (average 4.1 ± 2.6, n = 13) and Np/U ratios (average 14 ± 10, n = 13) in the oyster shells are clearly enhanced compared to the estimated one in the surface seawater, pointing out higher bioaccumulation of Np compared to Pu and U.