Nanoporous zeolite and its effect on the immobilization of trace elements in soils from scrap landfills under aided phytostabilization

The rising prerequisite for developing novel green remediation methods for trace-element-contaminated lands is allied to the necessity to really mend the soil environs. The effectiveness of zeolite-aided phytostabilization (AP) of soil contaminated with trace elements (TEs), from a scrap yard, using Lolium perenne as the plant for testing, was determined and discussed. The variability and activity of the rhizospheric bacterial community were also examined. The initial soil used in the AP experiment was characterized by especially high total contents of Zn, Pb, Cu and Cd. The TE total contents in roots and aboveground parts of L. perenne as well as in the phytostabilized soil materials were analyzed with flame atomic absorption spectrometry. The study revealed that the addition of natural zeolite into TE-contaminated soil increased the relative plant biomass as well as the soil pH value as compared to the phytostabilized non-amended series, whereas the total contents (with respect to an absolute value) of Zn, Pb, Cu and Cd were generally higher in roots than in the aboveground parts of L. perenne. In particular, the incorporation of zeolite to the soil contributed most significantly to the considerable relative decrease in the total contents of Cu, Pb, Cd and Zn in the soil, as well as the content of bioavailable and leachable speciations of Cd, Cu, Zn and Pb extracted from the soil using CaCl2 solution as compared to the non-amended series. In the phytostabilized zeolite-amended soil, the overall bacterial diversity decreased but the presence of zeolite favoured the growth of microorganisms belonging to Gammaproteobacteria, Planctomycetia, and Thermomicrobia, in particular, the genera Mycobacterium, Williamsia, and Prochlorococcus.