HR: 1400h
AN: OS23B-05    [Abstracts]
TI: Uranium and lanthanides in surficial sediments of Laguna Ojo de Liebre and evaporation ponds of Exportadora de Sal, Guerrero Negro, México.
AU: * Grajeda-Muñoz, M M
EM: mgrajeda@ipn.mx
AF: Centro Interdisciplinario de Ciencias Marinas-IPN, Av. IPN s/n, Col. Playa Palo de Santa Rita, Apdo postal 592., La Paz, BCS 23096, Mexico
AU: Choumiline, E
EM: eshumili@ipn.mx
AF: Centro Interdisciplinario de Ciencias Marinas-IPN, Av. IPN s/n, Col. Playa Palo de Santa Rita, Apdo postal 592., La Paz, BCS 23096, Mexico
AU: Zaposhnikov, D
AF: V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russian Federation
AB: To assess uranium and lanthanides behavior in hypersaline environments, surficial sediment samples were taken from Laguna Ojo de Liebre as well as from the evaporation ponds of Exportadora de Sal (the largest natural salt producing facility in the continent). A total of 63 surficial sediment samples from the laguna and 30 samples from the ponds were analyzed by inductive coupled plasma-mass spectrometry for uranium (sediments, deposits and solution) and instrumental neutron activation analysis for REEs in sediments and deposits. Results show that the behavior is all but similar between light and heavy REEs with the exception of Eu which shows a very different pattern of surficial distribution in Laguna Ojo de Liebre with a maximum concentrations in the sediments near the head of the lagoon. Data normalized with North American Shale Composite (NASC) show 3 distinct signature patterns on the surficial sediments, all of them enriched regarding the values of NASC. As for U total content in sediments and solid deposits it shows a higher concentration towards the head of the lagoon (3 mg/kg), from where the water is pumped to the sequence of evaporation ponds, with the lowest values being close to 1 mg/kg near the mouth of the lagoon. The interesting phenomenon begins in the evaporation ponds, where uranium is almost constant in sediments and deposits (0.15-1.5 mg/kg) but behaves conservately in the brine solution, increasing proportionally with salt content (U, 5-20 mg/kg; salt content, 40-250 g/kg). Non lithogenic U was calculated with Sc as reference. Most of the measured U was non lithogenic in the sediments of the lagoon and ponds. The distribution coefficient k= U(non-lith)/U(dis) shows a maximum value at ponds I and II (salt content 40-80 g/kg) decreasing with increasing salinity.
DE: 1050 Marine geochemistry (4835, 4845, 4850)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly