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Plastic has become the most widespread human-made material and small fragments (< 5mm, so called microplastics, MPs) accumulate in all the ecosystems. It is now admitted that the terrestrial environment represents an important sink for MPs and it has only recently become the focus of research, notably in ecotoxicology. In spite of a growing body of evidence regarding the potential effects of MPs on soil biota, more efforts are needed to address issues in this field. The aim of our study was to measure, at different levels of biological organization, the responses of Cantareus aspersus snail to low-density polyethylene (LDPE) particles dispersed in their food. Juvenile snails were exposed to a range of LDPE concentrations (10, 25, and 50% v/v) and sizes (median particle size (d50) of 120, 292, 340, and 560 μm). This study showed no snail feeding avoidance toward LDPE. The ingestion and digestion processes along the snail digestive tract did not lead to a measurable fragmentation of the MP particles. At the individual scale, big sized particles improved growth at the lowest exposure concentration tested, whereas at the molecular level, only small sized particles triggered oxidative stress but without causing quantifiable cyto- or genotoxic effects. The underlying mechanisms remain to be elucidated which strengthens the necessity to improve our knowledge on the effects of MPs on various biological models to better evaluate their environmental risks in terrestrial environments.

Environmental risk assessment of contaminated soils requires bioindicators that allow the assessment of bioavailability and toxicity of chemicals. Although many bioassays can determine the ecotoxicity of soil samples in the laboratory, few are available and standardized for on-site application. Bioassays based on specific threshold values that assess the in situ and ex situ bioavailability and risk of metal(loid)s and polycyclic aromatic hydrocarbons (PAHs) in soils to the land snail Cantareus aspersus have never been simultaneously applied to the same soils. The aims of this study were to compare the results provided by in situ and ex situ bioassays and to determine their respective importance for environmental risk assessment. The feasibility and reproducibility of the in situ bioassay were assessed using an international ring test. This study used five plots located at a former industrial site and six laboratories participated in the ring test. The results revealed the impact of environmental parameters on the bioavailability of metal(loid)s and PAHs to snails exposed in the field to structured soils and vegetation compared to those exposed under laboratory conditions to soil collected from the same field site (excavated soils). The risk coefficients were generally higher ex situ than in situ, with some exceptions (mainly due to Cd and Mo), which might be explained by the in situ contribution of plants and humus layer as sources of exposure of snails to contaminants and by climatic parameters. The ring test showed good agreement among laboratories, which determined the same levels of risk in most of the plots. Comparison of the bioavailability to land snails and the subsequent risk estimated in situ or ex situ highlighted the complementarity between both approaches in the environmental risk assessment of contaminated soils, namely, to guide decisions on the fate and future use of the sites (e.g., excavation, embankments, and land restoration). Integr Environ Assess Manag 2022;18:539-554. © 2021 SETAC.

Consumer products containing silver nanoparticles (AgNPs) release silver (Ag) to the environment, particularly wastewater. Sewage sludge (SS), which contains numerous contaminants including Ag, is recycled by spreading on agricultural land. Although slight impacts and bioaccumulation of Ag sulfide (Ag2S, the main species found in SS) in terrestrial organisms have been demonstrated, possible trophic transfer into plants and subsequently animal species has not been examined. Accordingly, the present study experimentally measured the transfer of Ag from AgNPs and sulfidized Ag into plants and primary consumers and compared their bioavailability. Nine plant cultivars were grown in soil mixed with SS containing Ag, which revealed that bioaccumulation of Ag by plants is species-dependent. Ryegrass (the plant species with the greatest accumulation – up to 0.2 mg kg−1) was then cultivated on a larger scale to expose snails and locusts for several weeks. While locusts did not accumulate Ag after two weeks of exposure, snails exhibited Ag bioaccumulation after 5 weeks when soil was accessible. Sulfidized Ag derived from AgNPs were less available (bioaccumulation up to 2.5 mg kg−1) than the Ag from the original AgNPs (bioaccumulation up to 15 mg kg−1). This transfer potential of Ag could have consequences for food webs due to chronic exposure linked to SS spreading practices. This study shows that transformations of AgNPs in treatment plants attenuate but do not completely eliminate the risk of Ag to plant and animal species SS.