Abstract
The overall objective of this thesis was to improve understanding of the influence of former mining sites on metal (Cd, Hg, Tl, Pb, Zn) and metalloid (As, Sb) contamination of the downstream hydrosystem. A special care was given to antimony (Sb), its behavior in mining-impacted streams remains poorly known and its isotopic signature could be usefull to track sources and processes. The study site is the Gardon River watershed in the south-east of France which drains many abandoned mining sites (Pb, Zn, Sb, coal). Metal and metalloid enrichment was studied in current and historical sediments of the Gardon River watershed. A sedimentary archive was used to investigate past metal contamination history. The prevailing metal and metalloid sources in sediments were determined together with the potential mobility of these elements toward the aqueous phase. In addition, dissolved and particulate metal and metalloid concentration variations were studied during a flood event using a high temporal resolution sampling. Altogether, the results suggest that former mining sites of the Gardon River watershed contribute to metal and metalloid enrichment of the downstream hydrosystem, especially during floods. More specifically, antimony behavior was investigated in a tributary of the Gardon River which is impacted by acid mine drainage originating from the disused Carnoulès mine and antimony isotopic composition was determined in waters collected in the Gardon River watershed and in the Upper Orb River after developing a protocol for preconcentrating and purifying Sb. The results highlight the potential of antimony isotopes to track the origin of this element and the processes that it undergoes during its transfer in streams impacted by mine drainage.