Search

Most current researches focus solely on reducing soil chromium availability. It is difficult to reduce soil Cr(VI) concentration below 5.0 mg kg-1 using single remediation technology. This study introduced a sustainable soil Cr(VI) reduction and stabilization system, Penicillium oxalicum SL2–nanoscale zero-valent iron (nZVI), and investigated its effect on Cr(VI) reduction efficiency and microbial ecology. Results showed that P. oxalicum SL2–nZVI effectively reduced soil total Cr(VI) concentration from 187.1 to 3.4 mg kg–1 within 180 d, and remained relatively stable at 360 d. The growth curve of P. oxalicum SL2 and microbial community results indicated that γ-ray irradiation shortened the adaptation time of P. oxalicum SL2 and facilitated its colonization in soil. P. oxalicum SL2 colonization activated nZVI and its derivatives, and increased soil iron bioavailability. After restoration, the negative effect of Cr(VI) on soil microorganisms was markedly alleviated. Cr(VI), Fe(II), bioavailable Cr/Fe, Eh, EC and urease (SUE) were the key environmental factors of soil microbiota. Notably, Penicillium significantly stimulated the growth of urease-positive bacteria, Arthrobacter , Pseudarthrobacter , and Microvirga , synergistically reducing soil chromium availability. The combination of P. oxalicum SL2 and nZVI is expected to form a green, economical and long-lasting Cr(VI) reduction stabilization strategy. [Display omitted] • P. oxalicum SL2–nZVI effectively reduced soil total Cr(VI) and available chromium. • Gamma-ray irradiation pretreatment facilitated P. oxalicum SL2 colonization in soil. • The negative effect of Cr(VI) on soil microorganisms was mitigated after remediation. • Cr- and Fe- related indicators, Eh, EC and SUE were the key environmental factors. • Penicillium colonization significantly stimulated the growth of urease-positive bacteria. [ABSTRACT FROM AUTHOR]

Cd contamination in rice urgently needs to be addressed. Nano hydroxyapatite (n-HAP) is an eco-friendly material with excellent Cd fixation ability. However, due to its own high reactivity, innovative application of n-HAP in the treatment of Cd contamination in rice is needed. In this study, we proposed a new application, namely n-HAP pre-treatment, which can effectively reduce Cd accumulation in rice and alleviate Cd stress. The results showed that 80 mg/L n-HAP pre-treatment significantly reduced Cd content in rice shoot by 35.1%. Biochemical and combined transcriptomic-proteomic analysis revealed the possible molecular mechanisms by which n-HAP pre-treatment promoted rice growth and reduced Cd accumulation. (1) n-HAP pre-treatment regulated gibberellin and jasmonic acid synthesis-related pathways, increased gibberellin content and decreased jasmonic acid content in rice root, which promoted rice growth; (2) n-HAP pre-treatment up-regulated gene CATA1 expression and down-regulated gene OsGpx1 expression, which increased rice CAT activity and GSH content; (3) n-HAP pre-treatment up-regulated gene OsZIP1 expression and down-regulated gene OsNramp1 expression, which reduced Cd uptake, increased Cd efflux from rice root cells. [Display omitted] • n-HAP pre-treatment could effectively reduce Cd accumulation in rice seedlings. • n-HAP pre-treatment modulated gibberellin and jasmonic acid synthesis pathways. • n-HAP pre-treatment regulated the expression of gene CATA1 and OsGpx1. • n-HAP pre-treatment influenced Cd transport related gene OsZIP1 and OsNramp1. [ABSTRACT FROM AUTHOR]