1 research outputs found
Bioaccumulation of CeO<sub>2</sub> Nanoparticles by Earthworms in Biochar-Amended Soil: A Synchrotron Microspectroscopy Study
The interactions of nanoparticles
(NPs) with biochar and soil components
may substantially influence NP availability and toxicity to biota.
In the present study, earthworms (Eisenia fetida) were exposed for 28 days to a residential or agricultural soil
amended with 0–2000 mg of CeO<sub>2</sub> NP/kg and with biochar
(produced by the pyrolysis of pecan shells at 350 and 600 °C)
at various application rates [0–5% (w/w)]. After 28 days, earthworms
were depurated and analyzed for Ce content, moisture content, and
lipid peroxidation. The results showed minimal toxicity to the worms;
however, biochar (350 or 600 °C) was the dominant factor, accounting
for 94 and 84% of the variance for the moisture content and lipid
peroxidation, respectively, in the exposed earthworms. For both soils
with 1000 mg of CeO<sub>2</sub>/kg at 600 °C, biochar significantly
decreased the accumulation of Ce in the worm tissues. Amendment with
350 °C biochar had mixed responses on Ce uptake. Analysis by
micro X-ray fluorescence (μ-XRF) and micro X-ray absorption
near edge structure (μ-XANES) was used to evaluate Ce localization,
speciation, and persistence in CeO<sub>2</sub>- and biochar-exposed
earthworms after depuration for 12, 48, and 72 h. Earthworms from
the 500 mg of CeO<sub>2</sub>/kg and 0% biochar treatments eliminated
most Ce after a 48 h depuration period. However, in the same treatment
and with 5% BC-600 (biochar pyrolysis temperature of 600 °C),
ingested biochar fragments (∼50 μm) with Ce adsorbed
to the surfaces were retained in the gut after 72 h. Additionally,
Ce remained in earthworms from the 2000 mg of CeO<sub>2</sub>/kg and
5% biochar treatments after depuration for 48 h. Analysis by μ-XANES
showed that, within the earthworm tissues, Ce remained predominantly
as Ce<sup>4+</sup>O<sub>2</sub>, with only few regions (2–3
μm<sup>2</sup>) where it was found in the reduced form (Ce<sup>3+</sup>). The present findings highlight that soil and biochar properties
have a significant influence in the internalization of CeO<sub>2</sub> NPs in earthworms; such interactions need to be considered when
estimating NP fate and effects in the environment