<p xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" class="first" dir="auto"
id="d12285058e164">The amount of engineered nanomaterials (ENMs) in the environment
has been increasing
due to their industrial and commercial applications. Different types of metallic nanoparticles
(NPs) have been detected in effluents from wastewater treatment plants (WWTPs). The
effluents have been reclaimed for crop irrigation in many arid and semi-arid areas.
Here, a soil micro-ecosystem was established including a microbiome, 4 Arabidopsis
thaliana plants, and 3 Eisenia fetida earthworms, for a duration of 95 days. The impact
of wastewater effluent (WE) containing aged NPs was studied. WE was taken from a local
WWTP and exhibited the presence of Ti, Ag, and Zn up to 97.0 ± 9.4, 27.4 ± 3.9, and
4.1 ± 3.6 µg/L, respectively, as well as the presence of nanoscale particles (1-100 nm
in diameter). The plants were irrigated with WE or deionized water (DIW). After 95
days, significantly higher concentrations of extractable Ti and Zn (439.2 ± 24.4 and
9.0 ± 0.5 mg/kg, respectively) were found in WE-irrigated soil than those in DIW-irrigated
soil (161.2 ± 2.1 and 4.0 ± 0.1 mg/kg). The extractable Ag concentrations did not
differ significantly between the WE- and DIW-irrigated soil. Although microbial biomass
carbon and nitrogen were not significantly reduced, the population distribution of
the microbial communities was shifted in WE-irrigated soil compared to the control.
The abundance of cyanobacteria (Cyanophyta) was increased by 12.5% in the WE-irrigated
soil as manifested mainly by an increase of Trichodesmium spp., and the abundance
of unknown archaea was enhanced from 26.7% in the control to 40.5% in the WE-irrigated
soil. The biomasses of A. thaliana and E. fetida were not significantly changed by
WE exposure. However, A. thaliana had a noticeable shortened life cycle, and corrected
total cell fluorescence was much higher in the roots of WE-irrigated plants compared
to the control. These impacts on the soil micro-ecosystem may have resulted from the
aged NPs and/or the metal ions released from these NPs, as well as other components
in the WE. Taken together, these results should help inform the reuse of WE containing
aged NPs and other components in sustainable agriculture.
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