Reactive transport of chromium in water circuits around the mine area of Libiola (Sestri Levante, Genoa)

Marina Accornero, a very brillant young researcher, investigated through her Thesis the fate of chromium in the acid mine drainage from the derelict mine of Libiola (Sestri Levante, Genoa). After carrying out a thorough review of the thermodynamic properties of aqueous species of chromium, she evaluated and experimentally determined the unknown properties of relevant aqueous complexes. Widespread solid phases in acid mine drainage frameworks, such as ferrihydrite and schwertmannite were also taken in due account. Then the distribution of several trace elements, including trivalent and hexavalent chromium, was modeled both in acid mine waters and upon mixing of acid mine waters with the surface waters of the Gromolo river. To this purpose, she become acquainted with powerful software codes, namely EQ3/6, for speciation-saturation calculations and reaction path modeling, and MINTEQA2, for modeling the surface complexation reactions occurring on precipitating ferrihydrite. These results are of utmost importance not only for elucidating the geochemical processes in the considered natural system, but also to proceed towards the mitigation of the acid mine drainage impact on the Gromolo aqueous system and biota. Besides the proposed methodology can be applied to other similar frameworks worldwide. (Luigi Marini).