Remediation of a heavy metals contaminated site with a botanical garden: monitoring results of the application of an advanced s/s technique

An innovative stabilization/solidification (S/S) technology called HPSS has been applied for the first time in a very delicate environment with a historical botanic garden in Venice for the remediation of a soil contaminated by heavy metals (As, Cu, Hg, Pb, Sb, Sn). This S/S technique, based on the High Performance Concrete (HPC) know-how (Scanferla et al., 2009), has been already successfully applied for the reconversion of different industrial contaminated sites into residential ones. The technology allows the remediation of contaminated soil fine fraction which is transformed into a very dense, low porous and mechanically-resistant granular material with the environmental characteristics for its reuse as filler in direct contact with the roots of the vegetal patrimony. More than 8,000 m(3) of contaminated soil fine fraction has been treated and monitored throughout 34 representative samples. Metal leachability was verified according to a leaching test method for granular waste (EN 12457-2, 2002) in which the demineralized water has been replaced with artificial sea water in accordance to Local Environmental Agency requirement. The mechanical properties were measured according to Los Angeles (LA) test method (BS EN 1097-2, 2010) for construction aggregates obtaining very good results in toughness and abrasion resistance. The granular material has been used tout court under the final floor layer in transit way and mixed with compost and soil in green areas also beside the rhizosphere horizon.