Abstract
The variation of dissolved and particulate metal(loid) concentrations was investigated during a Mediterranean flood in a former mining watershed, the Gardon River (SE France), using high-temporal resolution sampling. Dissolved antimony originating from the Upper Gardon River watershed underwent dilution during flood. Conversely, dissolved As and particulate As, Pb, Zn, Cd and Tl concentrations exhibited increased values during rising flood compared to low and receding flow conditions, with a double-peak shape. As, Pb, Cd and Tl concentration data in suspended particulate matter from this double-peak were distributed along two different correlation lines, showing the successive mobilization of two groups of particles highly enriched with As and Cd or Pb and Tl, both inherited from ancient Pb/Zn mines. Metal(loid) loads during the monitored 24h-flood event were: 0.5kg for Cd, 19.4kg for Sb and 204kg for As in the dissolved phase and 24kg for Cd, 38kg for Tl, 94kg for Sb, 1915kg for As, 2860kg for Pb and 5214kg for Zn in the particulate phase. Altogether, these results highlighted the importance of floods in the mobilization of metals and metalloids from ancient mining sites in Mediterranean regions, showing the need for high-temporal resolution monitoring of flood events to accurately assess the long-term contribution of mining activity to metal(loid) loads of downstream watershed.