The understanding and the identification of processes which influence mobility, transport and degradation of contaminants in groundwater are determining factors that have to be considered in polluted sites management, in order to correctly plan their remediation. This research deals with a case of complex contamination in central Adriatic Italy. The studied site is a residential area located on a coastal aquifer which is made up by sandy and silty sandy deposits up to 15 meters thick, laying on a plio-pleistocenic clayey aquiclude (Desiderio & Rusi, 2003). Here, groundwater is heavily polluted by metals (i.e. Fe, Mn e As), hydrocarbons and chlorinated solvents (i.e. PCE, TCE, DCEs, VC), due to several distinct pollution sources. As already known, the organic matter degradation, in this case related with an oil spill, triggers microbiological controlled redox processes in groundwater which involve redox-sensitive metallic species and chlorinated solvents (McCarty, 1997; Palmucci et al., 2016). In particular, the hydrocarbons degrades oxidising and acting as electron donors, while metallic species, as electron acceptors, are reduced and solubilised. Simultaneously, the chlorinated solvents degrades by mean of reductive dechlorination mechanism (i.e. from PCE to VC), acting as electron acceptors themselves. Nevertheless, since chlorinated solvents' reduction is not sometimes energetically favourable, heavily toxic by-products, as VC, can persist in groundwater. Thus, this dehalogenation process, when organic matter oxidises, competes with metallic species' reduction, complicating the dynamics which control the pollutants' diffusion in groundwater. In order to forecast the pollution's evolution in the aquifer, considering the hydrogeological framework, the numerical modeling of transport and hydrogeochemical processes has been implemented (Appelo & Postma, 2005), as a refinement and validation of the initial conceptual model. The dataset used in this study has been collected in 9 groundwater sampling rounds in the 2009-2014 period, soil samplings at different depths, and 2 hydraulic head measurement rounds. The monitoring network is made up by 43 points. The preliminary results confirm the metals' mobilisation linked with hydrocarbon pollution. This process seems to be more favoured than the reductive dechlorination, considering the very high concentrations of VC in the aquifer.
Multidisciplinary approach and modeling of a case of complex contamination in an Adriatic coastal aquifer
Di Curzio D.;Rusi S.
2016-01-01
Abstract
The understanding and the identification of processes which influence mobility, transport and degradation of contaminants in groundwater are determining factors that have to be considered in polluted sites management, in order to correctly plan their remediation. This research deals with a case of complex contamination in central Adriatic Italy. The studied site is a residential area located on a coastal aquifer which is made up by sandy and silty sandy deposits up to 15 meters thick, laying on a plio-pleistocenic clayey aquiclude (Desiderio & Rusi, 2003). Here, groundwater is heavily polluted by metals (i.e. Fe, Mn e As), hydrocarbons and chlorinated solvents (i.e. PCE, TCE, DCEs, VC), due to several distinct pollution sources. As already known, the organic matter degradation, in this case related with an oil spill, triggers microbiological controlled redox processes in groundwater which involve redox-sensitive metallic species and chlorinated solvents (McCarty, 1997; Palmucci et al., 2016). In particular, the hydrocarbons degrades oxidising and acting as electron donors, while metallic species, as electron acceptors, are reduced and solubilised. Simultaneously, the chlorinated solvents degrades by mean of reductive dechlorination mechanism (i.e. from PCE to VC), acting as electron acceptors themselves. Nevertheless, since chlorinated solvents' reduction is not sometimes energetically favourable, heavily toxic by-products, as VC, can persist in groundwater. Thus, this dehalogenation process, when organic matter oxidises, competes with metallic species' reduction, complicating the dynamics which control the pollutants' diffusion in groundwater. In order to forecast the pollution's evolution in the aquifer, considering the hydrogeological framework, the numerical modeling of transport and hydrogeochemical processes has been implemented (Appelo & Postma, 2005), as a refinement and validation of the initial conceptual model. The dataset used in this study has been collected in 9 groundwater sampling rounds in the 2009-2014 period, soil samplings at different depths, and 2 hydraulic head measurement rounds. The monitoring network is made up by 43 points. The preliminary results confirm the metals' mobilisation linked with hydrocarbon pollution. This process seems to be more favoured than the reductive dechlorination, considering the very high concentrations of VC in the aquifer.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
