Trace Element Enrichment Trends in the Southern Gulf of Mexico and Its Relationship with Oil Industry Activities. Chapter 11

²¹⁰Pb sediment dating is usefill to reconstruct historical contamination trends in aquatic environments. It is especially valuable to solve the lack of pre-anthropogenic baselines and long-term records, and allows assessment of both the impacts of industrial development and effectiveness of management measures for environmental protection. Temporal variations, within the past -100 years, of potentially toxic trace element (As, Ba, Co, Cr, Cu, Hg, Ni, Pb, V and Zn) concentrations, enrichment and fluxes were assessed in ²¹⁰Pb-dated sediment cores from offshore and intertidal locations in the southern Gulf of Mexico, with the purpose to estimate the potential oil industry impacts in the region. In offshore cores, the concentrations of As, Ba, Cu, Pb, V, and Zn were usually higher, and of Co, Cr, Hg, and Ni were usually lower, than in intertidal cores. Based on cluster analysis results, trace element concentrations were mostly influenced by sediment grain size and terrigenous contribution through fluvial discharges. Cr, Cu and Ni concentrations are naturally elevated in the region, reaching levels of potential ecological concern. Enrichment factors indicated the absence of contamination for most elements in most offshore cores; whereas contamination was observed in cores collected from areas influenced by major river discharges and flushing from Terminos Lagoon. There was a recent decrease in trace element fluxes in most cores, which could be caused by environmental controls established since the 1980s. However, around the Campeche Sound area, trace metal inputs were mostly attributed to wastewater discharges and land erosion in the adjacent coastal areas, associated with population growth and land use changes, promoted by the Campeche Sound oil production activities. Results highlight that environmental controls are needed for the offshore oil industry, and for the control of watershed erosion and untreated wastewater discharges to reduce contaminant loads to the marine environment.