Sedimentation Rate and Contamination Levels Profile of Potentially Toxic Elements in the Limoncocha Lagoon RAMSAR Wetland in the Ecuadorian Amazon

The aim of this study is to analyze the recent sedimentation rate in the center of the Limoncocha lagoon, a Ramsar site in the Ecuadorian Amazon, using the Pb-210 dating method and identifying the potentially toxic elements along a 50 cm sediment core. A strategy based on the application of three single and four integrated indices is used to evaluate trace element contamination with depth. Single indices show mainly As and Mo, and Cu, Ba, Cd, Ni, and Pb to a lesser extent, as responsible elements of a minor enrichment between -10 and -40 cm. The multielement slight pollution shows a mixture of potential contamination sources, probably due to agricultural, oil activities, and urban wastewater discharges. However, integrated indices applied, classify the complete core as without potential risk. The Pb-210(excess) profile shows three differentiated sections. A surface section where new materials with lower concentrations have been found, probably due to the underground currents that connect the lagoon and the nearby Napo River; a central section where CF-CS model and mass accumulation rate calculations provide a sediment accumulation rate of 0.56 +/- 0.03 cm y(-1); finally, a deeper section with a constant Pb-210(exces) profile, showing sediment reworking probably due to local flooding's.