Standard use conditions of terrestrial gastropods in active biomonitoring of soil contamination

The rehabilitation of contaminated sites is becoming a rising preoccupation which requires the knowledge of their past before realization of a suitable remediation. Physicochemical analysis must be realized jointly with the use of bioindicator organisms, which, owing to their bioaccumulation capacities, will reveal the bioavailability of metals in soils. Among terrestrial invertebrates, gastropods like Helix aspersa aspersa possess an important organotropism for metals in their digestive gland and they can be used in active biomonitoring. During in situ monitoring, two parameters are tested: growth and accumulation of Fe, Mn, Zn, Cu, Cd, Ni, Pb, and Cr in viscera of snails. Environmental conditions, like humidity or autochthonous vegetation, are able to modify growth or bioaccumulation. In order to remove the variation of these factors, microcosms previously used must be improved: they were equipped with porous candles, which continually humidify soil. Concerning vegetation, an experimental plan was realized to determine the combination of food with the best compromise between growth and bioaccumulation: the combination clover-snail feed was chosen. Thus, in situ, the experimental environment will be repeated in all investigated sites and used to allow follow up of their contamination levels and intercomparison between different sites.