An in vitro control study on soil micoremediation from heavy metals and Polycyclic Aromatic Hydrocarbons (PAHs).

Currently in Italy have been identified polluted sites named as SIN (sites of national interest) that need to remediation of soils, ground and/or surface waters and ground waters to avoid environmental damage and public health risks. Contaminated soils have historically been discharged at municipal solid waste landfills. SIN are characterized by generalized pollution of soils by solvents, metals and hydrocarbons. Different techniques have been used for contaminated soils remediation aimed to minimize their volumes to disposed of in landfills. Between the innovative techniques, the Phytoremediation is proposed as an alternative environmentally friendly thanks to the use of biological organisms. Our study have tested in vitro the ability to uptake and bioaccumulate of Trichoderma harzianum, Saccharomyces cerevisiae and Wickerhamomyces anomalus versus Ni, Cd, Cu, As, Zn, Cr, Pb, V, Hg and their degradation’s potential versus the sixteen PAHs defined also as priorities by the US EPA, for a possible application in soil bioremediation. Uptake capacity versus heavy metals and degradation’s capacity versus PAHs has been verified through controlled exposure of each species using four incremental exposure doses in fortified culture broth for the single heavy metal and, two incremental exposure doses for the PAHs standard mix. Analyses were carried out after specific and appropriate digestion of the samples and detection by ICP-MS Elan DRC-e Perkin Elmer for the heavy metals according to EPA method 6020b 2014 while the PAHs were extracted, purified and analyzed by HPLC UV/FL according to Conti et al., 2012. The uptake (%) of each heavy metal was calculated as average of the values obtained from the three independent replicates; for the sixteen PAHs tested we calculated the average percentage of degradation obtained by three independent replicates. Our data showed that all microorganisms used were able to accumulate all heavy metals to all different exposure doses. T. harzianum, S. cerevisiae and W. anomalus showed a better average performance for Cd (71.8%), As (73.2%), V(77.0%), Pb (63.3%), Hg (67.8%) the first; Ni (74.3%), Cd (71.3%), Cu (74.1%) and Hg the second; Ni (69,4%), Zn (70%), V (64.9%) and Hg (56.4%) the third. Only the Cr test have not given satisfactory results for the too acid pH (<2) of culture medium that has reduced the vitality of the microorganisms. A possible solution, would be to add an adequate buffer to the culture medium and perform the test again. All the microorganisms employed showed a good degradation capacity versus the sixteen PAHs tested, although, compared to T. harzianum, S. cerevisiae present the lower average percentages of absorption for acenaphthene, fluorene, anthracene, fluoranthene e benzo(b)fluoranthene, and W. anomalus for acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene benzo(b)fluoranthene, benzo(g,h,i)perylene. This test was useful to evaluate the better microorganism that can be used in symbiosis with a superior green plant to close the phytoremediation process against both excess of heavy metal and PAHs in the soil. Our data have shown that T. harzianum was the most performing microorganism. The superior green plant, once collected, may have alternative destinations as cogeneration of energy, biofuel production, thereby producing less waste material to confer in landfill. Then, bioremediation processes offer a good alternative compared to classical methods which require the use of physiochemical techniques more expensive, less faster and that involve the removal of the soil and its disposal in landfill, remaining an excellent alternative for the green economy.