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The combined contamination of terrestrial environments by metal(loid)s (MEs) and microplastics (MPs) is a major environmental issue. Once MPs enter soils, they can interact with MEs and modify their environmental availability, environmental bioavailability, and potential toxic effects on biota. Although research efforts have been made to describe the underlying mechanisms driving MP and ME interactions, the effects of MPs on ME bioavailability in terrestrial Mollusca have not yet been documented. To fill this gap, we exposed the terrestrial snail Cantareus aspersus to different combinations of polystyrene (PS) and arsenic (As), cadmium (Cd), or mercury (Hg) concentrations. Using kinetic approaches, we then assessed the variations in the environmental availability of As, Cd or Hg after three weeks of equilibration and in the environmental bioavailability of As, Cd or Hg to snails after four weeks of exposure. We showed that while environmental availability was influenced by the total ME concentration, the effects of PS were limited. Although an increase in As availability was observed for the highest exposure concentrations at the beginning of the experiment, the soil ageing processes led to rapid adsorption in the soil regardless of the PS particle concentration. Concerning transfers to snail, ME bioaccumulation was ME concentration-dependent but not modified by the PS concentration in the soils. Nevertheless, the kinetic approaches evidenced an increase in As (2- to 2.6-fold) and Cd (1.6-fold), but not Hg, environmental bioavailability or excretion (2.3- to 3.6-fold for As, 1.8-fold for Cd) at low PS concentrations. However, these impacts were no longer observable at the highest PS exposure concentrations because of the increase in the bioaccessibility of MEs in the snail digestive tract. The generalization of such hormetic responses and the identification of the precise mechanisms involved necessitate further research to deepen our understanding of the MP-mediated behaviour of MEs in co-occurring scenarios., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Human health risk assessment (HHRA) and ecotoxicological risk assessment (ERA) of contaminated soils are frequently performed separately and based on total soil concentrations without considering the concepts of mobility, bioaccessibility and bioavailability. However, some chemical and biological assays rarely used in combination can be applied to more accurately assess the exposure of organisms to metal(loid)s and thus to better estimate the links between soil contamination and effects. For humans, the unified bioaccessibility method (UBM) assesses oral bioaccessibility, while for soil fauna such as land snails, the bioaccumulation test reflects the bioavailability of contaminants. The aim of this study is to explore the relationship between oral bioaccessibility and the bioavailability of arsenic, cadmium and lead in twenty-nine contaminated soils. The results show a modulation of bioaccumulation and bioaccessibility of metal(loid)s by soil physicochemical parameters (organic matter especially). For the three metal(loid)s studied, strong relationships were modelled between the UBM and snail tests (0.77 < r² adj. <0.95), depending on the parameters of the linear regressions (contaminant and phases of the UBM test). The original models proposed demonstrate the feasibility of linking bioaccessibility to humans and bioavailability to snails and the relevance of their association for an integrative risk assessment of contaminated soils., (Copyright © 2019 Elsevier B.V. All rights reserved.)

To better understand the fate of metals in the environment, numerous parameters must be studied, such as the soil properties and the different sources of contamination for the organisms. Among bioindicators of soil quality, the garden snail (Cantareus aspersus) integrates multiple sources (e.g. soil, plant) and routes (e.g. digestive, cutaneous) of contamination. However, the contribution of each source on metal bioavailability and how soil properties influence these contributions have never been studied when considering the dynamic process of bioavailability. Using accumulation kinetics, this study showed that the main assimilation source of Cd was lettuce (68%), whereas the main source of Pb was the soil (90%). The plant contribution increased in response to a 2-unit soil pH decrease. Unexpectedly, an increase in the soil contribution to metal assimilation accompanied an increase in the organic matter (OM) content of the soil. For both metals, no significant excretion and influence of source on excretion have been modelled either during exposure or depuration. This study highlights how the contribution of different sources to metal bioavailability changes based on changes in soil parameters, such as pH and OM, and the complexity of the processes that modulate metal bioavailability.

For an accurate risk assessment of sites contaminated by trace elements (TE), measurements of bioavailability must be performed. This is routinely achieved using the standardized 0.01M CaCl2 method. However, the suitability of chemical extractions as proxies of bioavailability is questionable. We analyzed the correlations between chemically estimated TE bioavailability and TE actually accumulated by coupling plant and snails bioindicators. Results showed a better correlation between plant TE contents and CaCl2 fraction while total soil concentration better explained snail TE contents. However in both cases chemical measures were not suitable to predict TE accumulation and bioavailability. Considering the soil properties only improve the estimation of Cr, Ni and Pb accumulation by plants while for snails, TE contents in viscera were dependent both on soil and plant contents and soil properties. It highlights the complementarities of biomonitoring methods to assess bioavailability. This dual approach allows a "physiologically defined" evaluation of bioavailability., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A cross-transplantation field experiment was performed to investigate about possible adaptation/acclimatization to metal pollution in common garden snail Cantareus aspersus (ex-Helix aspersa) and brown-lipped grove snail Cepaea nemoralis populations. Adults were collected from an area surrounding a former smelter (ME), highly polluted by trace metals (TMs) for decades, and from an unpolluted site (BE). Subadults of first generation (F1) were exposed in microcosms in a 28-day kinetic study. Four exposure sites were chosen around the smelter along a soil pollution gradient (vegetation and soil otherwise comparable). Bioaccumulation in snail soft tissues globally increased with soil contamination, with Cd, Pb and Zn concentrations reaching 271, 187, 5527 μg g(-1), respectively. Accumulation kinetic patterns were similar between snail species but C. nemoralis showed greater TM levels than C. aspersus. Some inter-population differences were revealed in TM accumulation (bioaccumulation factors, accumulation kinetics) but did not suggest consistent adaptive responses. We did not detect negative effects of TM exposure on snail condition (body weight, shell size, shell weight). ME C. aspersus snails produced heavier shells than BE snails under exposure to TMs at the highest level, suggesting an adaptive response. The protocol used in this study, however, did not allow unambiguously distinguishing whether this response was due to genetic adaptation or to maternal effects. Abnormal but reversible shell development of adult ME C. nemoralis suggested physiological acclimatization. Differences in responses to TMs between populations are observed for conchological parameters, not for bioaccumulation, with different strategies according to the species (acclimatization or adaptation/maternal effects).

An As-contaminated soil (Unt) was amended with either iron grit (Z), a coal fly ash (beringite, B) or B + Z (BZ) and placed in lysimeters in 1997. An uncontaminated soil (R) was also studied. In summer and autumn 2003, lettuces were cultivated in the lysimeters and snails were caged for one month. Lettuce As concentrations were higher during the summer, while no differences occurred in snails between seasons. Snail As concentrations (μg g−1 DW) ranged from 2.5 to 7.0 in B, Z and BZ, and peaked at 17.5 in Unt. In summer, snail survival was affected in Unt and Z compared to R and B while no mortality was noticed in autumn. Snail growth decreased only in B, BZ and Unt in autumn. Snail As concentrations suggest a risk for their predators even on the remediated soils. [Copyright &y& Elsevier]

Environmental risk assessment of contaminated soils should ideally be carried out with complementary approaches (chemical and biological) conducted in situ and ex situ. While biological methods based on the assessment of effect and bioaccumulation in bioindicators exist for soil fauna organisms, such as land snails, the methodology is currently limited in the field to 14 metallic elements (MEs). To provide new relevant tools to the stakeholders of polluted fields, the aim of this work is to determine ex situ threshold guide values (ex situ TGVs) , for 15 MEs, 16 polycyclic aromatic hydrocarbons (PAHs) and 7 polychlorinated biphenyls (PCBs). These ex situ TGVs are the usual concentration of contaminants found in the viscera of the bioindicator Cantareus aspersus after 28 days of exposure to uncontaminated soils. The second objective was to assess and validate the relevance of these ex situ TGVs for the interpretation of contamination levels in various European contaminated soils based on global index calculations: i) The sum of the excess of transfers (SETs) and ii) the weighted SETs based on the general toxicity points of each contaminant used to evaluate the risk of transferred MEs, PAHs and PCBs (ERITMEs, ERITPAHs and ERITPCBs, respectively). In addition, the influence of soil physico-chemical properties on accumulation was modelled to better understand their roles in bioavailability. The presented ex situ TGV and the associated indicators (the global sum of the excess of transfers and global ecotoxicological risk) provide a basis by which stakeholders can prioritize the management of polluted soils depending on the risk they may represent. The determination of ex situ TGVs for organic and inorganic compounds provides new tools to characterize excess contaminant transfers, and it will also allow the use of snails for ERAs, notably for common pollutants, such as PAHs and PCBs for which guide values are not available. Unlabelled Image • Threshold guide values (TGVs) available for 38 organic and inorganic contaminants. • TGVs will help in the assessments of the contamination levels and bioavailability. • TGVs guide stakeholders in their choice of polluted soil management practices. [ABSTRACT FROM AUTHOR]