Le titane dans les sédiments de l'assainissement pluvial urbain : sources, concentrations, mobilités

Abstract

RÉSUMÉ MOTS-CLÉS : sédiments urbains, titane, mobilité potentielle, signature géochimique ABSTRACTTitanium is largely used in the urban environment. The purpose of this study is to characterize the titanium geochemical signature in urban stormwater sediments. Firstly, we compared the titanium, iron, silica, copper, zinc and lead content in 800 river sediments collected in Europe with the content of 19 urban sediments collected in stormwater infiltration basins in Lyon. Even if the total titanium content is not higher in urban sediment (mean of 2,7 g/kg) than in river sediments (1,5 à 4,0 g/kg), urban sediments concentrate titanium in comparison to other main minerals like silica and is correlated to heavy metals. Thus, the urban environment produce eroded particles that have a specific geochemical signature. Secondly, the study of the potentiel soluble or colloïdal mobility of titanium in urban sediment through batch experiments shows that titanium has a very low mobility in soluble or colloïdal form (less than 0,005% of the total titanium content). The organic matter present in urban sediment is supposed to play a major role on the limitation of the mobility of colloïdal titanium.