Mercury in Biota and Surficial Sediments from Coatzacoalcos Estuary, Gulf of Mexico: Distribution and Seasonal Variation

Variation of mercury (Hg) in sediments and biota from Coatzacoalcos estuary during the dry, rainy and windy seasons was estimated. In sediments, Hg concentrations ranged from 0.07 mu g g(-1) in site 13 (Ixhuatepec) located upstream, to 1.06 mu g g(-1) in site 3 (Coatzacoalcos river), located in the industrialized area. Highest enrichment factor (EF) and index of geoaccumulation (I (geo)) in surficial sediments were 53 and 5.1 respectively. From EF and I (geo), it is considered that Coatzacoalcos estuary is from moderately contaminated to contaminated. In most fish species from Coatzacoalcos estuary, the sequence of Hg concentration was liver > muscle > gills. Average Hg concentrations in soft tissue of bivalves ranged from 0.09 mu g g(-1) in Corbicula fluminea to 0.18 mu g g(-1) in Polymesoda caroliniana. Biota-sediment accumulation factor (BSAF) ranged from 0.9 in P. caroliniana during the rainy season (site 4) to 3.8 in P. caroliniana from the same site during the windy season.