Spatial and seasonal mercury distribution in the Ayapel Marsh, Mojana region, Colombia.

Geographical and temporal changes of total mercury (T-Hg) concentrations in sediments, macrophytes and fish were evaluated in the Ayapel Marsh, Mojana, Colombia. Sampling was conducted during 2006-2007, including both rainy and dry seasons, and T-Hg was measured using atomic absorption spectroscopy. Distribution of T-Hg in sediments and the macrophyte Eichhornia crassipes showed that higher concentrations were found along the flooding pathway of the Cauca River. Hg has also polluted the food chain. Highest T-Hg concentrations in fish were detected for the carnivorous Pseudoplatystoma fasciatun (0.432 ± 0.107 µg/g, fresh weight [fw]), and lowest in the non-carnivorous Prochilodus magdalenae (0.143 ± 0.053 µg/g, fw), with differences between trophic levels. T-Hg for fish samples (0.298 ± 0.148 µg/g, fw) did not exceed the limit consumption level (0.50 µg/g, fw). It is concluded that mercury-polluted sediments from the Cauca River, contribute to Hg deposition into the Ayapel Marsh. Accordingly, interventions must be conducted to decrease Hg accumulation in fish.

Hallazgo de mercurio en peces de la ciénaga de Ayapel, Córdoba, Colombia / Finding of mercury in fish from the Ayapel marsh, Cordoba, Colombia

Objetivo. Determinar las concentraciones de mercurio total (Hg-T) en algunas especies de peces de la ciénaga de Ayapel (Colombia). Materiales y métodos. Los muestreos fueron realizados desde Julio de 2004 a Junio de 2005, incluyendo las épocas seca y lluviosa. Las muestras fueron analizadas por espectrometría de absorción atómica por vapor frío después de digestión ácida. Resultados. Las concentraciones más altas de Hg-T se observaron para las muestras analizadas de la especie carnívora Ageneiosus caucanus (0.504±0.103 mg Hg kg-1 peso fresco), y las menores concentraciones en la especie Iliófaga Prochilodus magdalenae (0.130±0.056 mg Hg kg-1 peso fresco). Las concentraciones más altas fueron encontradas en las muestras de la época seca. Los niveles promedio de Hg-T en las muestras de peces no excedieron el límite para consumo humano establecido por la Organización Mundial de la Salud (OMS, 0.5 mg Hg Kg-1 peso fresco). Conclusiones. La evaluación del riesgo basado en el índice de peligrosidad sugiere que el consumo de 0.12 kg de pescado por día en la población humana (principalmente carnívoros) podría incrementar el riesgo de envenenamiento por mercurio en la población local.

Objetive. To establish total mercury (Hg-T) concentrations in some fishes speciesin the Ayapel marsh (Colombia). Materials and methods. Sampling was conducted from July 2004 to June 2005, including both the dry and rainy seasons. Hg-T was analized by cold vapor atomic absorption spectroscopy after acid digestion. Results. The highest concentrations in Hg-T were observed for analized samples of the carnivorous specie Ageneiosus caucanus(0.504±0.103 mg Hg kg-1 fresh weight), and the lowest concentrations in the Iliophagus specie Prochilodus magdalenae (0.130±0.056 mg Hg kg-1 fresh wt). The highest Hg-T concentrations were found in the samples of the dry season. The Hg-T mean levels for fish samples did not exceed the human limit consumption level according to the World Health Organization (WHO, 0.5 mg Hg kg-1 fresh weight). Conclusions. The risk assessment based on the hazard index suggested that the consumption of 0.12 kg per day of fish (mainly carnivorous) could increase the risk of mercury poisoning in the local population.