Modeling Unsaturated–SaturatedFlow and Nickel Transport inFractured Rocks

摘要

This study investi gated the modeling of variably saturated fl ow and Ni transport in fracturedrocks at a site (Altamura, southern Italy) polluted in 2001 by unauthorized sludgewaste disposal. Time-lapse electrical resisti vity tomography (ERT) and infi ltrometer experimentalresults were used to constrain near-surface boundary conditi ons in an unsaturatedfl ow model. A plasti c ring was used as an infi ltrometer because its experimental setupis very versati le and adaptable to many diff erent geological conditi ons, taking into consideration irregulariti es in the soil and rock surfaces. The proposed methodology allowsswitching from the tomography to the map of water pressure contour lines obtained by themodel by making the ti me-lapse ERT an eff ecti ve tool to reduce computati onal uncertainties. Simulati on results predicted both the concentrati on and the residence ti me of the Niin the vadose zone of the Altamura site. These results were used to successively investi gatethe horizontal Ni transport into the deep fractured aquifer. Simulati ons provided apparentNi pathways in the groundwater and expected concentrati ons in a downstream well, placed10.9 km from the contaminati on sources. The agreement of the results with the samplingdata collected has confi rmed that the groundwater was polluted for 16 mo by Ni. The contamination plume started during the winter of 2004 and moved in the groundwater towardthe sea at an average velocity of 10 m/d.