Submarine groundwater discharge (SGD) has been identified as an

important source of Sr to the ocean and the SGD-driven Sr flux to the

global ocean has been recently re-evaluated (Beck et al. 2013). However,

the uncertainty of this value is still high because of the uncertainties

related to the determination of SGD flow rates and the paucity of

87Sr/86Sr data in SGD end-members. As carbonates have high Sr

concentrations and are subjected to intense heightened weathering, they

might significantly influence the SGD input of Sr to the ocean. Here we

present data on Sr concentrations and 87Sr/86Sr ratios in three carbonate

dominated sites of the western area of the Mediterranean Sea, a semienclosed

basin characterized by abundant coastal carbonates. The

87Sr/86Sr ratios in groundwater were lower compared to modern seawater (~

0.70916), as expected for areas dominated by carbonate lithologies.

Concentrations of Sr and 87Sr/86Sr ratios in groundwater showed

conservative mixing in the studied subterranean estuaries. By using SGD

flow rates reported in the literature for the study areas, a meteoric

SGD-driven Sr flux of (0.12 - 2.1)·103 mol d-1 km-1 was calculated for

the region, with a fresh SGD end-member characterized by a Sr

concentration of 27 - 30 μM and a 87Sr/86Sr ratio of 0.708020 - 0.707834.

Integrating these Sr data with literature data (i.e. values of Sr

concentration and 87Sr/86Sr ratio from other lithologies as well as SGD

flow rates), we also calculated the fresh SGD-driven Sr flux to the

entire Mediterranean Sea, obtaining a value of (0.34 - 0.83)·109 mol y-1,

with a 87Sr/86Sr of 0.7086 - 0.7081. Thus, for the entire Mediterranean

basin, SGD is globally a source of Sr less radiogenic compared to

seawater. The SGD Sr flux to the Mediterranean Sea represents 5-6% of the

SGD Sr flux to the global ocean and the Mediterranean SGD end-member has

higher Sr concentration (5.0 - 12 μM) than the global SGD end-member (2.9

μM). This confirms the significant role of carbonate lithologies on SGDdriven

Sr fluxes to seawater.

The fresh SGD-driven Sr flux to the Mediterranean Sea is about 20 - 50%

of the riverine Sr input and significantly higher than the input through

atmospheric dust deposition. Therefore SGD should be considered as an

important continental source of Sr to the basin.