Hydrogeochemistry of Bagnara spring (Umbria, Italy) and possible relationship with seismic activity

摘要

The Bagnara spring is located within the seismically active area of the Umbria-Marches Apennine. Spring composition varies with time from a calcium carbonate type to a calcium carbonate-sulfate type and can be explained as the result of a mixing of shallow groundwater dominated by calcium carbonate component and deeper groundwater dominated by a sulfate component. A tritium measurement indicates a residence time of few years for the calcium-carbonate end member and 30-40 years for the deep sulfate end member. The variation in time of the sulfate concentration at Bagnara does not appear to have any direct relation with the discharge rates or with the rainfall distribution, but major changes have been observed in correspondence with seismic events suggesting a possible correlation between the change in the composition of the spring and the occurrence of earthquakes.