Bioaccumulation of CeO₂ Nanoparticles by Earthworms in Biochar-Amended Soil: A Synchrotron Microspectroscopy Study

Abstract

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 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/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- and biochar-exposed earthworms after depuration for 12, 48, and 72 h. Earthworms from the 500 mg of CeO/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/kg and 5% biochar treatments after depuration for 48 h. Analysis by μ-XANES showed that, within the earthworm tissues, Ce remained predominantly as CeO, with only few regions (2-3 μm) where it was found in the reduced form (Ce). The present findings highlight that soil and biochar properties have a significant influence in the internalization of CeO NPs in earthworms; such interactions need to be considered when estimating NP fate and effects in the environment.

Trophic Transfer and Transformation of CeO2 Nanoparticles along a Terrestrial Food Chain: Influence of Exposure Routes

“…It seems that the large reduction of Ce occurred in the snail DG only after ingestion, for Ce(IV) species predominate in the plant tissues and feces. The reduction of CeO 2 NPs has been observed in several species, such as Escherichia coli, 43 plants, 12 nematodes, 44 earthworms, 45 and freshwater snails. 34 Moreover, we have demonstrated that natural reducing substances and organic acids in root exudates play important roles in the reduction of CeO 2 NPs in plants.…”

Analytical Methods for Nanomaterial Determination in Biological Matrices

“…The former, however, can create two-dimensional images that are accurate representations of the latter technique and can generate three-dimensional pictures by measuring the elemental distribution of the monitored analyte. The spatial resolution of a synchrotron-generated XRF beam is normally between 1 and 10 m, but some XRF beams have a spatial resolution of up to 100 m. Beamlines for sub-micrometer analysis are available and provide a spatial resolution of up to 100 nm [ 33 ].…”

Assessment of TiO2 Nanoparticles on Maize Seedlings and Terrestrial Isopods Under Greenhouse Conditions

“…Interestingly, most studies have been done with earthworms (74.1%), isopods (16.28%), and collembola (9.30%), and the majority carried out under laboratory conditions, but the main reason for the use of these organisms is because they are the classes of invertebrates with the highest representation in biomass and the with ability to decompose and transform OM (Kautz and Topp 2000). They appear to be suitable as bioindicator organisms for ecotoxicity studies on new xenobiotics such as nanoparticles (Flaccavento et al 2019;Servin et al 2018). For this experiment, even when demonstrated adverse effects under greenhouse conditions, these data let us suggest that in agricultural or forestry area, TiO 2 NPs may impact organisms' populations.…”