Combined influence of nZVI and arbuscular mycorrhizal fungi on heavy metal uptake by maize (Zea mays L.)

Antonio Roberto Valero Powter

Master's thesis

Abstract:

Nanoscale zero-valent iron (nZVI) is an efficient amendment for immobilizing metal(loid)s (e. g. Zn, Cd, Cr, Pb, As...etc) in the soils, due to its high specific surface area, strong reducibility and high surface reactivity. However, nZVI functions may be influenced by plants and microbes, and nZVI can also pose toxicity to those living organisms. Therefore, before application, nZVI behavior and its functions in plant-microbial-soil system should be elucidated. Arbuscular mycorrhizal (AM) fungi are biquitous soil fungi that can make symbioses with most terrestrial plants, they can provide plants with mineral nutrients, and in return get carbohydrates from plant partners. AM symbiosis can also enhance plant tolerance to metal(loid)s and influence metal(loid) behavior in plant-soil system, but its influence on nZVI functions towards metal(loid) is still unclear. Thus the present study mainly focused on the influence of AM symbiosis on nZVI functions, as well as the effects of nZVI on AM symbioses formation. Maize (Zea mays L.) plants were inoculated with/without AM strains Rhizophagus irregularis, and grown in a "real" metal(loid) contaminated soil amended with/without 0.5% nZVI. AM colonization status was assessed, and uptake of mineral nutrients (P, Fe, Ca, K, Mg), as well as various metal(loid)s (i.e. Zn, Pb, Cu, Mn, Cd, Cr, As, Ni) by plants were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The results showed that although in a heavily contaminated situation, AM fungi can still make symbiosis with maize plants, but nZVI addition showed certain negative influence on AM symbioses formation. nZVI and AM generally had no influence on plant growth and macro nutrients (e.g. P, K, Ca, Mg) acquisition. nZVI amendment generally decreased some metal(loid)s (e.g. Mn, Pb, Cr, Ni, As) uptake by plant roots, showing stabilization functions of nZVI on metal(loid)s. However, when plants were inoculated with AM fungi, the stabilization functions of nZVI decreased, showing the negative influence of AM symbiosis on nZVI functions. Especially, it is interesting to find that AM symbiosis generally increased metal(loid)s uptake by plant roots when nZVI was amended into the soils. Besides, AM symbiosis generally enhance metal(loid) immobilization in plant roots and reduce metal(loid) transport from roots to shoots.In summary, the study confirmed the counteractive effects of AM symbiosis and nZVI on plant metal(loid) uptake, and revealed the negative influence of nZVI on AM development, as well as the significant influence of AM symbiosis on nZVI functions towards metal(loid) stabilization.

Keywords

Arbuscular mycorrhizal fungi, Nano zero-valent iron, Metal(loid)s uptake, Zea mays. L, Soil contamination

Language used: English

Date on which the thesis was submitted / produced: 20. 4. 2017

Thesis defence

• Supervisor: Songlin Wu
• Reader: Zhongbing Chen

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Master programme / field:
Geology / Environmental Geosciences