The present research investigates the presence of Fe and Mn in groundwater of central Adriatic Italy, in order to identify the most probable origins of the contaminants and the hydrogeochemical processes that cause contamination. More than 2,500 chemical analyses, undertaken between 2010 and 2012 from a monitoring network of 653 sampling points, were assessed. The study analyzed the Apennine carbonate aquifers, the alluvial aquifers of the intramontane basins and of the Adriatic alluvial plains. On selected samples, a pre-filtering treatment using 0.22 µm and standard 0.45 µm pore size filters was executed in order to evaluate the influence of the solid phases of Fe and Mn on the groundwater contamination. In addition to the above, approximately 360 sampling results were assessed from 302 soil monitoring points. The spatial distribution of Fe and Mn indicates that both of them are present in all the examined aquifers, with high concentrations widely spread only in the alluvial aquifers. Both the hydrogeochemical and statistical analysis highlight the presence of Fe and Mn in groundwater is totally independent from the chemistry of the main ions, while there is an inverse correlation with NO3 and Eh. These correlations clearly suggest that the mobilization of the two metals is ruled by the redox processes that occur in the aquifers. The importance of redox processes in the mobilization of Fe and Mn was assessed using the threshold concentrations of redox sensitive species. Fe and Mn concentrations detected in soils are generally significant and this confirms the idea that soils could represent a real source for these metals, potentially able to originate contamination of groundwater. In order to evaluate anthropic influence on Fe and Mn contamination of groundwater, the presence of anthropogenic pollutants, such as pesticides and hydrocarbons, was considered. The comparison between pesticides and Fe and Mn doesn’t indicate significant correlations and this suggest that their presence in groundwater is not related to the use of pesticides and fertilizers. On the contrary the highest concentrations of total hydrocarbons are generally related with high levels of Fe and Mn. This connection is linked with the redox conditions that the presence of hydrocarbons can establish. In conclusion, water-rock interaction, combined with redox conditions, are considered the main process affecting Fe and Mn enrichment in groundwater.

Redox processes affecting Fe and Mn groundwater contamination in central adriatic italy.

PALMUCCI, WILLIAM;DI CURZIO, DIEGO;RUSI, Sergio
2016-01-01

Abstract

The present research investigates the presence of Fe and Mn in groundwater of central Adriatic Italy, in order to identify the most probable origins of the contaminants and the hydrogeochemical processes that cause contamination. More than 2,500 chemical analyses, undertaken between 2010 and 2012 from a monitoring network of 653 sampling points, were assessed. The study analyzed the Apennine carbonate aquifers, the alluvial aquifers of the intramontane basins and of the Adriatic alluvial plains. On selected samples, a pre-filtering treatment using 0.22 µm and standard 0.45 µm pore size filters was executed in order to evaluate the influence of the solid phases of Fe and Mn on the groundwater contamination. In addition to the above, approximately 360 sampling results were assessed from 302 soil monitoring points. The spatial distribution of Fe and Mn indicates that both of them are present in all the examined aquifers, with high concentrations widely spread only in the alluvial aquifers. Both the hydrogeochemical and statistical analysis highlight the presence of Fe and Mn in groundwater is totally independent from the chemistry of the main ions, while there is an inverse correlation with NO3 and Eh. These correlations clearly suggest that the mobilization of the two metals is ruled by the redox processes that occur in the aquifers. The importance of redox processes in the mobilization of Fe and Mn was assessed using the threshold concentrations of redox sensitive species. Fe and Mn concentrations detected in soils are generally significant and this confirms the idea that soils could represent a real source for these metals, potentially able to originate contamination of groundwater. In order to evaluate anthropic influence on Fe and Mn contamination of groundwater, the presence of anthropogenic pollutants, such as pesticides and hydrocarbons, was considered. The comparison between pesticides and Fe and Mn doesn’t indicate significant correlations and this suggest that their presence in groundwater is not related to the use of pesticides and fertilizers. On the contrary the highest concentrations of total hydrocarbons are generally related with high levels of Fe and Mn. This connection is linked with the redox conditions that the presence of hydrocarbons can establish. In conclusion, water-rock interaction, combined with redox conditions, are considered the main process affecting Fe and Mn enrichment in groundwater.
2016
Rendiconti Online della Società Geologica Italiana
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11564/643375
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