Fe-Mn oxide modified biochar decreases phthalate uptake and improves grain quality of wheat grown in phthalate-contaminated fluvo-aquic soil.

We used a pot experiment to investigate the effectiveness of 0.5, 1.0, and 2.0% biochar (BC) or iron-manganese oxide modified biochar (FMBC) additions on the biomass, enzyme activity, and grain quality of wheat plants grown in dibutyl phthalate (DBP) and di-(2-ethylhcxyl) phthalate (DEHP) polluted fluvo-aquic soils, as well as the bioavailability of DBP and DEHP. BC and FMBC applications significantly reduced DBP and DEHP accumulation in grains, which enhanced the content of starch and protein-related enzyme, thereby improving yield, and starch and protein content in wheat grains and increasing the content of minerals including Fe, Mn, K and Ca. Molecular docking assays showed that DBP and DEHP could bind to starch synthase (GBSS) through hydrogen bonds and intermolecular forces, which may have hindered the entry of substrates or occupied the binding sites of the reactants, thus inhibiting the activity of GBSS. In addition, FMBC treatment had a better inhibitory effect on the phytotoxicity of DBP and DEHP on wheat grain than BC treatment. This result might be attributed to the fact that FMBC has more functional groups and porous structure, and larger specific surface area. In summary, these findings contribute to our understanding of the mechanism of phthalate phytotoxicity, which may help us prevent/reduce it in the future.