Pilot testing of a bioremediation system for water and soils contaminated with heavy metals: vegetable depuration module

We present a novel constructed wetland called a vegetable depuration module (VDM) as a pilot test of a bioremediation system (BS) for decontaminating water and soil polluted with heavy metals. The VDM consisted of a pool filled with stones of different granulometry and a substrate top layer composed of a mixture of soil and volcanic ash (50:50, v/v) supplemented with 350 ppm Zn. The BS of sunflower plants colonized by the arbuscular mycorrhizal fungus <i>Rhizophagus intraradices</i> was planted in the VDM. Initially, the substrate registered high concentrations of Zn, Cr, Mn, Cu, and Sr, and had Eh &gt; +500 mV and pH 8.4. Irrigation with a Cu solution by vertical flow was carried out. After 3 months, bioaccumulation factors ranged from 1.00 to 8.90, and translocation rates were &gt;1 for Sr and Cu. Total metals extracted by the BS and percolation were 31%, 34%, 50%, 45%, and 57% for Zn, Cu, Mn, Cr, and Sr, respectively. Only the BS was capable of extracting 94% of Cu and 38% of Zn. VDM allowed us to calibrate the extractive performance of the studied elements in BS. This biotechnological development holds great potential for phytoremediation of polluted areas.