Isotopic and chemical study of lake Massaciuccoli, Tuscany, hydrodynamic patterns, water quality and anthropogenic impact

Lake Massaciuccoli (7 km2, 15 km north of Pisa, Tuscany), occupies a shallow depression on a coastal marshy plain. The lake is connected to the sea by a 8 km channel with sluices fl owing through an old sandpit pond. Hydrochemistry and stable isotopes are applied to investigate water, salt and nutrient inputs into the lake from drainage channels, groundwater and the sea. In general, the ion concentrations plotted versus Cl- suggest mixing with seawater, but do not allow to discriminate between contributions of continental water versus seawater -- which vary seasonally -- nor between those from farming practices and redox processes. Vice-versa, hydrochemistry and isotopic tracers (2H, 11B, 13C, 18O, 34S) combined together, highlight the water mass dynamics and the role of continental waters, show the organic matter cycles and the anthropogenic contributions, and allow to defi ne the main redox processes and their rates.