Fitorisanamento di un sito ex-discarica: variazioni della qualità del suolo

The aim of the study was to assess the effects of a phytoremediation system on the quality of soil contaminated by heavy metals (HM) in a former dump. In March 2008 the selected plants (Populus nigra var. Italica, Cytisus scoparius, Paulownia tomentosa) were planted. Total and DTPA-extractable HM, microbial biomass and its activity (respiration and enzyme activities) were determined in twelve soil samples collected in February 2008 and 2010 at 0-30 cm depth. After two years of phytoremediation the system was able to reduce soil HM and to increase the respiration and the enzyme activity per unit of biomass. Moreover, the results show that the CHCl3-labile forms of HM, determined by the fumigation-extraction method, may represent a new approach to assess HM availability to microbial biomass. An appreciable increase of the HM availability and mobility was registered, probably because of the effect of root exudates. This increase may represent the cause of the soil microbial biomass eco-physiological stress.