Sources of environmental radioactivity in sediments of south of Gulf of Mexico

Full text: Environmental radioactivity studies in sediments of the South of Gulf of Mexico were carried out to understand the distribution and concentration patterns of natural and artificial radionuclides in the Mexican marine sedimentary environment. These studies are unique in this area of the Gulf of Mexico. Twenty three USNEL BoxCores sediments were collected in water depths between 20 to 2000 m in the Southern Gulf of Mexico. The USNEL BoxCores sediments were collected aboard R/V Justo Sierra during the OGMEX XI, XII and XIII Oceanographic Cruises for the summers of 1993, 1994 and 1995. The 30-cm deep sediment cores were sub-sampled in 2-cm thick slides, and frozen for later analyses. The natural 40K, 208Tl, 214Bi, 214Pb, 212Pb 228Ac and artificial 137Cs radionuclides concentrations were measured using a Ge-Li Hp Gamma-Spectrometer, and counting for 50-60000 seconds with ±5% uncertainty. The measurements were made at the Laboratorio de Vigilancia Radiologica Ambiental del Centro at Cienfuegos, Cuba. On the basis of the measured natural and artificial radionuclides concentrations, three provinces were identified: continental shelf, continental slope and carbonate provinces. The distribution and concentration of natural radionuclides is a function of fluvial, fluvial-lagoonal sediments discharges, and horizontal circulation patterns (geostrophic) and wind driven circulation. The highest natural radionuclides concentrations were found in sediments at water depths between 300 to 1500 m. This may be attributed to incoming Loop Current vortices which interact with bottom topography and collide with the western and southern Gulf of Mexico boundaries, decreasing their circulation energy and consequently allowing for the deposition of the natural and artificial radionuclides contained within the rings' water mass. (author)