Analytical Sciences

Fluoride Content by Ion Chromatography Using a Suppressed Conductivity Detector and Osmolality of Bitterns Discharged into the Pacific Ocean from a Saltworks: Feasible Causal Agents in the Mortality of Green Turtles (Chelonia mydas) in the Ojo de Liebre lagoon, Baja California Sur, Mexico

Luis Raúl TOVAR,  Ma. Eugenia GUTIÉRREZ, and Guillermo CRUZ

Center for Interdisciplinary Research on the Environment and Development, National Polytechnic Institute, Av. Miguel Othón de Mendizabal 485, 07738 México D.F., México

On December 1997, 94 corpses of green turtles, Chelonia mydas, were found at the Ojo de Liebre lagoon (OLL) adjacentto the industrial operation of Exportadora de Sal S. A (ESSA), the largest saltworks in the world, owned by the Mexican Government and Mitsubishi Corporation, located in Baja California Sur, Mexico. Every year about 551 x 10⁶ m³ of seawater is solar evaporated, producing 7 x 10⁶ tons of salt and 24.6 x 10⁶ m³ of bitterns, the latter being discharged into the OLL, which is a costal lagoon of the Pacific Ocean. ESSA claimed that bitterns contain the same salts present in seawater, but 20-fold more concentrated than the former. Ion chromatography with a conductivity detector and ion suppression was used to determine the F^-, Cl^-, SO₄^2- and CO₃^2- contents of seawater, brines and bitterns collected at ESSA. Furthermore, the osmolality of brines and bitterns from ESSA was measured. F^- content in bitterns was 60.5-fold more than that in seawater. The bitterns osmolality was 11000 mosm/kg of water, whereas the turtle's plasma osmolality was about 400 mosm/kg of water. We concluded that the dumping of bitterns into the ocean should be avoided.

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