@article{Tassi_Bicocchi_Cabassi_Capecchiacci_Vaselli_Capezzuoli_Brogi_2014, title={Hydrogeochemical processes controlling water and dissolved gas chemistry at the Accesa sinkhole (southern Tuscany, central Italy)}, volume={73}, url={https://www.jlimnol.it/jlimnol/article/view/jlimnol.2014.961}, DOI={10.4081/jlimnol.2014.961}, abstractNote={<p>The 38.5 m deep Lake Accesa is a sinkhole located in southern Tuscany (Italy) that shows a peculiar water composition, being characterized by relatively high total dissolved solids (TDS) values (2 g L<sup>-1</sup>) and a Ca(Mg)-SO<sub>4 </sub>geochemical facies. The presence of significant amounts of extra-atmospheric gases (CO<sub>2</sub> and CH<sub>4</sub>), which increase their concentrations with depth, is also recognized. These chemical features, mimicking those commonly shown by volcanic lakes fed by hydrothermal-magmatic reservoirs, are consistent with those of mineral springs emerging in the study area whose chemistry is produced by the interaction of meteoric-derived waters with Mesozoic carbonates and Triassic evaporites. Although the lake has a pronounced thermocline, water chemistry does not show significant changes along the vertical profile. Lake water balance calculations demonstrate that Lake Accesa has >90% of its water supply from sublacustrine springs whose subterranean pathways are controlled by the local structural assessment that likely determined the sinking event, the resulting funnel-shape being then filled by the Accesa waters. Such a huge water inflow from the lake bottom (~9ยท10<sup>6</sup> m<sup>3</sup> yr<sup>-1</sup>) feeds the lake effluent (Bruna River) and promotes the formation of water currents, which are able to prevent the establishment of a vertical density gradient. Consequently, a continuous mixing along the whole vertical water column is established. Changes of the drainage system by the deep-originated waters in the nearby former mining district have strongly affected the outflow rates of the local mineral springs; thus, future intervention associated with the ongoing remediation activities should carefully be evaluated to preserve the peculiar chemical features of Lake Accesa.</p>}, number={3}, journal={Journal of Limnology}, author={Tassi, Franco and Bicocchi, Gabriele and Cabassi, Jacopo and Capecchiacci, Francesco and Vaselli, Orlando and Capezzuoli, Enrico and Brogi, Andrea}, year={2014}, month={May} }