RESUMEN

Rare earth element (REE) mobility in the environment is expected to be controlled by colloids. Recent research has detailed the structure of iron-organic colloids (Fe-OM colloids), which include both large colloids and smaller nano-colloids. To assess how these nano-colloids affect REE mobility, their interactions with REE and calcium (Ca) were investigated at pH 4 and 6. Using Asymmetric Flow Field Flow Fractionation (A4F) combined with UV and Triple Quadrupole Inductively Coupled Plasma Mass Spectrometry (QQQ-ICP-MS), Fe-OM nano-colloids were separated from bulk Fe-OM colloids and their REE and Ca content were analyzed. Without REE and Ca, nano-colloids had an average diameter of approximately 25 nm. Their structure is pH-dependent, with aggregation increasing as pH decreases. At high REE loadings (REE/Fe ≥ 0.05), REE induced a size increase of nano-colloids, regardless of pH. Heavy REE (HREE), with their high affinity for organic matter, formed strong complexes with Fe-OM colloids, resulting in large aggregates. In contrast, light REE (LREE), which bind less strongly to organic molecules, were associated with the smallest nano-colloids. Low REE loading did not cause noticeable fractionation. Calcium further enhanced the aggregation process at both pH levels by neutralizing the charges on nano-colloids. These findings indicate that REE can act as aggregating agent controlling their own mobility, and regulating colloid transfer.

RESUMEN

Most studies on nanoplastics (NPs) focus on aquatic environments, overlooking their combined bioaccumulation with pollutants in terrestrial ecosystems. This study addresses a part of this gap by investigating how polystyrene nanoplastics (PS-NPs) affect the bioaccumulation and translocation of lead (Pb) in Hordeum vulgare L. plants. Using the RHIZOtest device for precise soil contamination control, we quantified PS-NPs (50 nm) in plant shoots via pyrolysis-gas chromatography/mass spectrometry (Py-GCMS) after plant KOH digestion. Our findings revealed that PS-NPs reduce Pb bioaccumulation and make adsorbed Pb onto PS-NPs less bioavailable to plants. For the highest Pb concentration, the Pb uptake index (PUI) followed the trend: Free Pb > NPs + Pb > Pb primary adsorbed by NPs, showing reduced Pb translocation to shoots in the presence of PS-NPs. Moreover, the presence of Pb decreased the bioavailability of PS-NPs probably in response to PS-NPs aggregation or modified charge. The PS-NPs concentrations in shoots range from 275.2 to 400 µg g-1, representing 3.9 to 5.75% of the total PS-NPs. This study highlights the intricate interactions between nanoplastics and metals in soil-plant systems and emphasizes the need for further research on their combined effects and potential risks to food safety.

Asunto(s)

Hordeum , Plomo , Poliestirenos , Contaminantes del Suelo , Hordeum/metabolismo , Hordeum/efectos de los fármacos , Plomo/metabolismo , Contaminantes del Suelo/metabolismo , Contaminantes del Suelo/análisis , Nanopartículas , Brotes de la Planta/metabolismo , Brotes de la Planta/química , Bioacumulación , Plásticos/metabolismo , Microplásticos

RESUMEN

Metal contaminants were found in a soil amended with a compost produced from household waste that included plastic debris. A strong correlation between the microplastics (MPs) distribution and the metal concentrations in the soil profile. Metals in the highest concentrations corresponded to the most significant plastic additives. As the total amount of plastic debris and the loss of metals and plastic particles were unknown, it was not possible to conclude that plastic debris is responsible for all of the metal contamination. Amount of calcium (Ca) in MPs (24.5 g kg-1 of MPs) are high in response to it use as filler in plastic formulation. As strontium (Sr) is an analogous of Ca, the potential of 87Sr/86Sr ratios to quantify MPs and nanoplastics (NPs) was tested. Elemental concentrations (Ca, Cd, Cr Pb, Ni and Sr) coupled with Sr isotopic ratios were compared in both amended soil and a reference soil without amendment. The 87Sr/86Sr ratios of the amended soil were less radiogenic than for the reference soil (0.724296 ± 0.000010 against 0.726610 ± 0.00009 for the 0-5 cm soil layer, respectively). The Sr isotopic ratio of MPs was also significantly less radiogenic (0.711527 ± 0.000010 for the 0-5 cm soil layer) than for soils. The MPs< 2 mm occurred in the ploughed soil depth with concentration varying from 1.19 to 0.09 mg kg-1. The NPs concentration stayed quite constant from 0 to 55 cm at around 0.25 µg kg-1. The presence of NPs until 55 cm soil depth was attested by the detection of polypropylene NPs by Py-GCMS in the soil solution < 0.8 µm. These results highlighted, for the first time, the NPs mobility throughout the soil depth and their ability to reach hydrosystems. It also demonstrated that Sr could be a potential tracer of the MPs< 2 mm and NPs amount occurring in soils.