Late Holocene evolution of the lower Tagus alluvial plain and heavy metals content : preliminary results

This paper aims to contribute to the fluvial dynamic knowledge of the Lower Tagus during the late Holocene. Two cores were done in selected geomorphological positions at the alluvial plain. Each ten centimeters of sediments were submitted to sedimentological and geochemical analyses in order to identify human contamination by heavy metals, sedimentation rates and environmental changes in the main channel position The main conclusions are: (1) The witness of the lateral migration of the fluvial channel; (2) The very irregular sedimentation rate, from 3mm per year to 0.1mm per year; (3) The diversified contamination of fluvial sediments and fluvial channels by heavy metals, namely Cu due to cooper sulphate vineyards and Pb due to petrol and Cr from the tanning industries.