Identifying sedimentation processes in the Coata River, Altiplano of the Puno department, Peru, by the 210Pb method

The rivers, lakes and dam sediment analyses are able to predict the back conditions of these ecosystems and determine how the environment changed as a result of anthropogenic activities. In this way they can be used as important management tools of water resources. The activity and distribution of the 210Pb in the sedimentary record resulted in a study that sought to evaluate the sedimentation rate chronology in three sedimentary profiles in the Coata River, Southern Peru, in order to follow historical changes in the past 100–150 years. Beside this, the geochemical distribution of the trace metals Ba, Zn, Cu, Cr, Ni and Co was evaluated in the sediments, allowing investigation of their potential contamination and impact over the river. The research involved the determination of some specific aspects of the sediments such as the main oxides, organic matter and granulometry, as well the physicochemical analysis of the surface waters, with the objective of assisting the interpretation of the results obtained in the sediments. The dating process was based on the 210Pb method and the Constant Flux: Constant Sedimentation Model—CF: CS was adequate. It allowed determination of distinct sedimentation rates in each profile, between 0.36 and 0.74 g/cm2 year, corresponding to linear sedimentation rates of 0.28–0.66 cm/year. The evaluation of the excess/unsupported 210Pb data permitted characterizing sediments with maximum ages between 36 and 96 years. This geochemical study showed that the recorded metals in the sediments may be a consequence of more recent anthropogenic activities in the environment and that the 210Pb is a useful method to evaluate the sedimentation history.