Four iron and aluminium-based products, notably red mud (RM), hematite (Fe2O3), an iron-rich water treatment residual (Fe-WTR) and amorphous Al hydroxide (Al-OH) were evaluated for their effectiveness at fixing As and heavy metals (i.e. Cd, Cu, Pb, Zn) in a circumneutral contaminated soil [As (2105•mg Kg-1), Cd (18•mg Kg-1), Cu (264•mg Kg-1), Pb (710•mg Kg-1), Zn (522•mg Kg-1)] and influencing soil microbial and biochemical features (i.e. microbial biomass-C, microbial counts, 16S rRNA PCR-TTGE of culturable bacteria, dehydrogenase, urease and β-glucosidase activity, Biolog derived parameters-AWCD and richness) as well as bean (Phaseolus vulgaris) and wheat (Triticum vulgare) growth. After 6 months equilibration, all the amendments (application rate 3% w/w) but RM caused a significant reduction of labile As while only Al-OH reduced significantly the concentration of water-soluble heavy metals. Despite the highest bioavailability of contaminants, most of the soil microbial and biochemical features monitored (i.e. microbial biomass-C, total bacterial counts, dehydrogenase activity and AWCD) were significantly higher in the RM-soil. However, bean germination was completely inhibited in RM-soil while wheat growth was not dissimilar from that of control soil. On the contrary, Al-OH revealed the best treatment promoting microbial abundance, diversity and activity while stimulating bean and wheat growth by approx. 3 and 2.5 fold respectively and reducing significantly the amount of As accumulated in plant shoots. It is concluded that Al-OH can be a suitable candidate for future field evaluation trial while the use of RM in the remediation of circumneutral or subalkaline contaminated soils should be reconsidered and carefully evaluated. This is the first report acknowledging a clear detrimental effect of RM on metal(oid)s bioavailability in soil and plant growth.
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|Titolo:||Stabilising metal(loid)s in soil with iron and aluminium-based products: microbial, biochemical and plant growth impact|
|Data di pubblicazione:||2014|
|Appare nelle tipologie:||1.1 Articolo in rivista|