Natural arsenic contamination in waters from the Pesariis village,NE Italy |
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| Authors: | R Petrini F Slejko A Lutman S Pison G Franceschini L Zini F Italiano A Galic |
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| Institution: | 1.DST, Università di Trieste,Trieste,Italy;2.Dipartimento di Udine,ARPA-FVG,Udine,Italy;3.DISGAM,Università di Trieste,Trieste,Italy;4.Sezione di Palermo,INGV,Palermo,Italy |
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| Abstract: | High arsenic (As) concentrations, >900 μg/L, were measured in Ca–Mg–SO4 waters from springs and drainages in the village of Pesariis in the Carnic Alps (NE Italy). Oxidation of the outcropping
arsenian marcasite ore deposits of the area is proposed as the mechanism for As release into oxygenated waters during runoff.
Nevertheless, the limited extension of the ore deposit and the relatively low As content of the mineralization suggest that
sulfide weathering might not be the only process responsible for the highest As concentration in groundwaters. An additional
mechanism involves As adsorption onto ferric iron particulate during oxidation, the drawdown in reducing environment at depth
during water infiltration, and the release of ferrous iron and sorbed arsenic to the water columns by reductive dissolution
of hydrous ferric oxides (HFO). This yields the observed Fe–As correlation. Newly formed HFO precipitates when groundwaters
discharge to aerated conditions, leading to the removal of As, which strongly partitions into the iron-rich sediments, adsorbed
onto the surface of amorphous Fe2O3·xH2O. The calculated and measured As concentration in sediments exceeds 10% by weight. Furthermore, geochemical and isotopic
data indicate that the As-rich reservoir partly mixes with shallower aquifers, commonly tapped for drinking supply, representing
a natural hazard for inhabitants. |
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