Valutazione della compromissione biologica di un suolo contenente ceneri di pirite in un progetto di fitorisanamento

Biological health assessment of a pyrite cinder containing soil in a phytoremediation project The applicability of phytoremediation to an industrial area where pyrite cinders from a sulphuric acid production process had been discharged for a long time was investigated . Physical and chemical analysis of pyrite cinders pointed out high levels of Cu and As together with a texture mainly based on silt and fine sand and a deficiency in plant nutrients. Plant growth limiting factors have been identified by means of physical, chemical and biological analysis carried on a mixture (1:1, w/w) of the cinders and the soil covering cinders in the polluted site Plant bioassays (watercress germination, barley root elongation, lettuce dry biomass yield) indicated, together with the high potential toxicity of cinders, a low actual toxicity, and the effectiveness of mixing them with a topsoil covering the polluted area in order to reduce phytotoxicity. Moreover, bioassays showed that manure and compost were able to improve the poor agronomic quality of the mixture. Arsenic and copper in soils can affect soil microbial function and community composition and, therefore, may have effects on soil ecosystem functioning. The microbial properties of the mixture have been investigated by analysing through a polyphasic approach the bacterial community structure and by evaluating its microbial function thorough the Community Level Physiological Profile (CLPP). The number of total and metal tolerant heterotrophs and actinomycetes was determined by the viable plate count method; species diversity of total bacterial community and of culturable fraction was investigated (DGGE). The number of culturable bacteria as well as the biodiversity degree was found to be comparable with that of different heavy metal polluted soils. CLPP showed the capability of the microbial community of degrading various sugars, amino acids and carboxylic acids but few aromatic compounds provided. The most of isolates identified by sequencing 16SrRNA gene and belonging to different genera were metal resistant Qualitative and quantitative composition of the bacterial community, its catabolic versatility together with soil positive response to amendments suggest a potential success in bioremediation technologies.