posted on 2023-12-12, 12:20authored byDong Liu, Shahid Iqbal, Heng Gui, Jianchu Xu, Shaoshan An, Baoshan Xing
To
understand microplastic–nanomaterial interactions in
agricultural systems, a randomized block 90-day pot experiment was
set up to cultivate ryegrass seedings in a typical red sandy soil
amended with compost (1:9 ratio). Polyvinyl chloride (PVC) and polyethylene
(PE) microplastic (MP) contaminants were added into pot soils at 0.1
and 10%, whereas nano-Fe3O4 (as nanoenabled
agrochemicals) was added at 0.1% and 0.5% in comparison with chemical-free
controls. The combination of nano-Fe3O4 and
MPs significantly increased the soil pH (+3% to + 17%) but decreased
the total nitrogen content (−9% to – 30%; P < 0.05). The treatment group with both nano-Fe3O4 and PE had the highest total soil C (29 g kg–1 vs 20 g kg–1 in control) and C/N ratio (13 vs
8 in control). Increased rhizosphere nano-Fe3O4 concentrations promoted ryegrass growth (+42% dry weight) by enhancing
the chlorophyll (+20%) and carotenoid (+15%) activities. Plant leaf
and root peroxidase enzyme activity was more significantly affected
by nano-Fe3O4 with PVC (+15%) than with PE (+6%).
Nano-Fe3O4 significantly changed the ryegrass
bacterial community structure from belowground (the rhizoplane and
root endosphere) to aboveground (the phylloplane). Under MP contamination,
the addition of nano-Fe3O4 increased bacterial
diversity (+0.35%) and abundance (+30%) in the phylloplane and further
intensified the connectivity of ryegrass aboveground bacterial networks
(positive association increased 17%). The structural equation model
showed that the change in the plant microbiome was associated with
the rhizosphere microbiome. Overall, these findings imply the positive
influences of nano-Fe3O4 on the soil–microbe–plant
system and establish a method to alleviate the harmful effects of
MP accumulation in soils.