Methods for Toxicity Assessment of Contaminated Soil by Oral or Dermal Uptake in Land Snails: Metal Bioavailability and Bioaccumulation

Abstract

Using two biological characteristics of the land snail (subspecies Helix aspersa aspersa and Helix aspersa maxima), i.e., soil eating and crawling on wet surfaces, methods were developed to assess the bioavailability of heavy metals (Cd, Cr, Pb, and Zn) from soil and aqueous leachates of soil. Measurement of heavy-metal concentrations in soil, leachates, and soft tissues of snails showed that contamination from ingested soil is the major route for metal uptake. Generally, the concentrations of metals were greater in the viscera than in the foot and rose with the proportion of spiked soil (Sl) in the diet. After ingestion of soil, bioaccumulation factors in the viscera were over two for Cd (3.5-27) and Zn (1.7-4.4) for both subspecies but were below one for Cr (0.04-0.6, except for H. aspersa maxima: 1.21) and Pb (0.02-0.23). Contamination by leachate Sl mainly caused accumulation of Cr in the tissues. Determining the metal burden per snail enables an estimation to be made of the risk of secondary poisoning encountered by predators. The present study provides data on the bioavailability of metals in soils and on the relationships between bioaccumulation and sublethal effects.

How terrestrial snails can be used in risk assessment of soils

“…Figure 3 shows the increasing accumulation of Cd in the foot and the viscera of snails exposed to increasing Cd contamination of the food or the substrate. The accumulation of Cd is higher in the viscera than in the foot, as observed previously [13–15]. Snails exposed to contaminated food reached very high Cd concentration, with bioaccumulation factors in the viscera decreasing from 6.3 to 3.6 with increasing exposure concentration.…”

“…For Pb and Cr, snails exposed to spiked soils were found previously to be deconcentrators [15]. The present results confirm these data and suggest a low bioavailability of these metals in the sewage sludge that leads to ICs far from those known to induce toxic effects [15,24]. Thus, growth inhibition could result from additive, synergic, and antagonist effects between metals, PAHs, or other nonanalyzed chemicals, like the linear alkylbenzene sulfonates or nonylphenol that frequently are found in sludge [40].…”

“…Cadmium concentrations were measured by laboratories 3 and 5 in the food (one replicate) and in the substrate (three replicates) by atomic absorption spectrometry (flame or furnace, depending on the concentration) after digestion in 50% nitric acid according to the method described by Coeurdassier et al [13]. Cadmium concentrations in snail tissues (foot and viscera) were analyzed by laboratory 5 at the end of the ring test; for each modality of exposure, five snails were used for Cd analysis according to the method described by Gomot de Vaufleury and Pihan [15]. Chemical analysis of the natural soil, the ISO artificial substrate, and the sewage sludge was performed by the IRH laboratory (Vandoeuvre les Nancy, France) according to Association Françaisede Normalisatio standardized methods (XP × 33–012 for polychlorinated biphenyls; NFT 90–115 for polycyclic aromatic hydrocarbons [PAHs]; NF EN ISO 11885 for Cd, Cr, Cu, Ni, Zn, and As analysis; and NF EN 1483 for Hg analysis).…”

Transfer of Cd, Cu, Ni, Pb, and Zn in a soil‐plant‐invertebrate food chain: A microcosm study

“…3A). The transfer of Cd from soil to snails is known to occur by two exposure routes: Digestive [22], and dermal [4]. However, to our knowledge, the contribution of soil as a contamination source in the total bioaccumulation of Cd has not been studied; therefore, the present data are the first concerning this issue, which needs further investigation to verify some of the above‐mentioned assumptions.…”

Morphometry of the epidermis of an invasive megascoelecid earthworm (Amynthas gracilis, Kinberg 1867) inhabiting actively volcanic soils in the Azores archipelago

“…The integument is highly permeable, and not only serves as the sole respiratory surface, but may also be the predominant uptake route for metals such as Cd, Cu, and Pb (Vijver, Vink, Miermans and Van Gestel 2003). The structure, dimensions, and composition of epidermal surfaces have been widely used for assessing the effects of xenobiotics on molluscs (Gomot-de Vaufleury and Pihan, 2002), fish (Lamche and Burkhardt-Holm, 2000), amphibians (Fenoglio et al, 2009), and mammals (Fullerton and Hoelgaard, 1988;Iwata et al, 1999), but surprisingly in view of its anatomical features and direct interfacing with soil, not in earthworms. Thus, the main objective of the present investigation was to determine morphometrically the effect of a volcanic soil on the epidermis of a cosmopolitan endogeic earthworm species (Amynthas gracilis Kinberg, 1867; Megascolecidae) resident in the Azores by comparing populations with different exposure histories confined within mesocosms in field locations with and without volcanic activity.…”