Chemical and isotope composition of waters from Firenzuola railway tunnel, Italy

Abstract: Forty-six water points from stream waters, springs, wells and tunnel seeps have been monitored for major reactive aqueous components and isotope composition of water over the period 2004-2008 in an area (Mugello basin, Northern Apennines, Italy) impacted by the tunneling works for the Bologna-Firenze high-speed railway. Based on geological, hydrogeological and geochemical information, an integrated conceptual model has been elaborated which considers the drainage of waters of different age in the Firenzuola railway tunnel. Precipitations and waters from small perched aquifers rapidly percolate in the tunnel through well-defined fractures zones and mix with more than 100 years old waters. Dilute, near neutral pH waters of Ca-HCO3 composition are generated through limited interactionof meteoric waters with local lithologies, whereas more saline, alkaline pH waters of Na-CO3-HCO3 composition originate through prolonged interaction of meteoric waters with flysch rocks.