Bioaccumulation of 238U and 239+240Pu in bivalve mollusks from different coastal areas of Mexico

Uranium and plutonium isotopes were determined in bivalve mollusks from several coastal areas of Mexico. Four specimens of clam (Gallo, Chocolata, Chirla and Pata de Mula) and one of oyster (American) were acquired at a local distribution center. The radionuclides were extracted and purified using radiochemical procedures and measured by alpha spectrometry. In most cases, the activity concentration values of uranium and plutonium ​​were greater in the shell than in the soft body of bivalves. The activity concentrations of ²³⁸U and ^239+240Pu in the bivalve shell were between 0.21 and 1.29 Bq/kg, and 0.02 and 0.21 Bq/kg, respectively. The values ​​for ²³⁸U and ^239+240Pu in the soft body of bivalves were between 0.06 and 1.14 Bq/kg, and 0.004 and 0.09 Bq/kg, respectively. Hierarchical cluster analyses applied to data analysis revealed that the majority of samples were grouped into two clusters identified as Gulf of Mexico and Mexican Pacific due to their origin. Hence, the differences in activity concentrations may be associated with the content of the radionuclides in the medium where the specimen was developed. The accumulation of actinide elements in bivalve mollusks may be useful to evaluate the level of contamination due to heavy metals in the Mexican marine environment.