Release And Speciation Of Uranium In Low-Ionic-Strength Groundwaters At An Abandoned Uranium Mine In Val Vedello (Orobic Alp-Italy) By Adsorptive Cathodic Stripping Voltammetry

Adsorptive cathodic stripping voltammetry (AdCSV) with HDME and a chloranilic acid ligand was used in the trace analysis of uranyl ions at pH = 2 in low-ionic-strength groundwaters around mining areas. Upon optimization, the limit of detection around 0.10 mu g L-1 was found with linearity up to 10 mu g L-1. In the abandoned mining area of Val Vedello (Orobic Alps, Italy), measured uranium concentrations in water ranged from 0.3 mu g L-1 above the uranium mineralization levels to 145 mu g L-1 in groundwaters percolating from mine galleries. Such uranium concentrations are related to natural weathering effects of CO2 and/or hydrogen carbonate ion on uranium mineralizations under oxic conditions. A marked seasonal dependence was then found, in agreement with literature data on a pre-operational survey dating back to 1980-1981. No significant chemical impact of the abandoned mining activity on groundwater quality could be found. Accordingly, no significant increase in contaminants derived from the heat-burn of explosives, such as chloride and nitrate, in groundwaters from mine galleries was found.