Effects of land use change and sediment mobilization on coastal contamination (Coatzacoalcos River, Mexico)

Coastal ecosystems are subject to many anthropogenic pressures, including pollution and the enhancement of sedimentation due to human activities. The lower reach of the Coatzacoalcos River is considered to be the most polluted coastal area of Mexico due to the presence of major petrochemical production centers in its watershed. In order to show the impact of land use change and industrial activities on the adjacent coastal environment of the Coatzacoalcos River, we reconstructed the historical changes of sediment transport and trace metals contamination based on the study of a 210Pb dated sediment core. Several geochemical indicators, such as clay mineral content, the concentrations of reference elements (Al, Ca, Sr, Rb) and the carbon isotope ratio (δ13C) revealed a change of sediment and contamination sources since the early 80s, in coincidence with the large industrial and urban development in the area. We conclude that the increased contaminant loads were related to terrestrial sources, likely contaminated and eroded soils from the catchment, due to extensive land use changes. Although the contaminant enrichment since the early 80s was low, As, Hg and Ni concentrations show potentially dangerous levels and exceed the USEPA-ERL concentration benchmarks, thus constituting a potential threat to marine aquatic life and humans through seafood consumption.