The Venice Lagoon is worldwide considered as a typical example of the human impact on the surrounding ecosystem. The development of the industrial zone of Porto Marghera begun in 1917 as an extension of the Venice Port, in order to sustain activities related to oil and coal, as well as to exploit the railway system. Despite the recent decrease in the number of employees, Porto Marghera is still one of the most important chemical districts in Italy. This study reports early results from the ongoing in-situ phytoextraction of potentially toxic elements (Cd, Hg, Zn) within the industrial area of Porto Marghera. Two agronomic plant species with high annual biomass yield (Helianthus annuus L., Brassica juncea (L.) Czern.) were used. This paper also reports the microcosms and mesocosms tests to evaluate the efficacy of the treatments to be applied to the in-situ phytoextraction process of the polluted site. The combined use of EDTA and Ammonium Thiosulfate during phytoextraction increases the efficiency of Cd, Hg, Zn removal from contaminated soil.