Arsenic mobilization in groundwater at quirra plain (Sardinia, Italy)

The plain of Quirra in Sardinia is subjected to persistent As contamination, which affects soils, sediments and the shallow aquifer exploited in summer for watering part of the land. The upstream abandoned mining area of Baccu Locci is the primary source of As pollution. A hydrodynamic model of the shallow aquifer (water level less than 3 m below the surface) has been performed by Pilia (2005) and the results of this study serve as a starting point to investigate As distribution in groundwater and to produce a reactive transport model in the central part of the aquifer. High dissolved As content in groundwater (up to 1 mgL(-1)) is observed only in areas frequently overflooded with contaminated sediments. When a reactive transport model is performed, it is observed that dissolved As is adsorbed along the flow direction according the isotherm S = 0.00054-(Fe(total)C0.88)-C-2.4. (total) where S is As adsorbed by sediments (mgkg(-1)), Fe is total dissolved iron (mgL(-1)) and C is dissolvedAs (mgL(-1)).