Trace Metals (Cd, Cu, Hg, and Pb) Accumulation Recorded in the Intertidal Mudflat Sediments of Three Coastal Lagoons in the Gulf of California, Mexico

²¹⁰ Pb geochronologies of Cd, Cu, Hg, and Pb fluxes were obtained from the intertidal mudflat sediments of the coastal lagoons Chiricahueto, Estero de Urías, and Ohuira in the Mexican Pacific. The Cu and Hg sediment concentrations at the three lagoons fell within the ranges of 6-76 μg g⁻¹ and 0.1 to 592 ng g⁻¹, respectively; Chiricahueto and Estero de Urías sediments had comparable Cd and Pb concentrations within the ranges of 0.2-2.1 μg g⁻¹ and 10-67 μg g⁻¹, respectively; whereas in Ohuira lagoon, Cd concentrations were lower (0.1-0.5 μg g⁻¹) and Pb concentrations were higher (115-180 μg g⁻¹) than in the other lagoons. The metal fluxes μg cm⁻² y⁻¹) for the three lagoons fell within the ranges of 0.02-0.15 for Cd, 0.7-6.0 for Cu, 0.001-0.045 for Hg, and 0.7-20 for Pb. The Hg pollution in Estero de Urías was attributed to the exhausts of the thermoelectric plant of Mazatlan and the metal enrichment in Chiricahueto and Ohuira was related to the agrochemical wastes from the croplands surrounding these lagoons.