Study on removal of pyrene by Agropyron cristatum L. in pyrene-Ni co-contaminated soil

Heavy metals and polycyclic aromatic hydrocarbons (PAHs) co-contamination in the soil is widespread. Phytoremediation is often used to remediate co-contaminated soil, but few studies focused on the effects of nickel on the dissipation and uptake of pyrene in phytoremediation. The dissipation of pyrene, the uptake, and distribution of pyrene in Agropyron cristatum L. (A. cristatum) were investigated in this study in the presence of nickel. The pyrene removal rate in single pyrene-contaminated soil with A. cristatum cultivation (48.97%) was the highest, which was higher than that of the co-contamination (47.88%). This was due to the high soil microbial activity and high dissolved organic matter (DOM) contents. In single pyrene-contaminated soil, pyrene was mainly accumulated in the soluble fraction in shoots and on the cell wall in roots of A. cristatuma. Besides, nickel could promote the adsorption of pyrene on the cell wall. Pyrene in A. cristatum could be transported through the apoplast and symplast, and the pyrene contents in the symplast were 2-3 times that of the apoplast. The uptake of pyrene by A. cristatum included both active absorption and passive transportation. Active absorption involved H⁺ transport and energy conversion processes, and passive transport was associated with water protein channels.