Historical reconstruction of trace element concentrations and fluxes in a tropical coastal lagoon (Mexican Pacific) derived from Pb-210 radiochronology

摘要

The historical trends of trace element concentrations, enrichments and flux ratios were evaluated through the analysis of three Pb-210-dated sediment cores from the tropical coastal system Xola-Paraman Lagoon (XPL), a Ramsar site at the Mexican Pacific coast. The depth profiles of lithogenic elements (Al, Si, Rb, Sr, Zr) were relatively homogeneous, while concentrations of trace elements, such as Ni, Cu, Zn, As and Pb, showed highest values during the last four decades. Only minor enrichments of Ni, Cu, Zn and As were observed. With a chemometric approach, we identified three major processes controlling the variability of elements among the sedimentary records: 1) input of lithogenic materials; 2) periodical marine-water intrusion and 3) complexation between metal ions and organic matter. The changes of trace element flux ratios over time closely reproduce the intensification of agricultural activities around the lagoon and the impact of major tropical storms.