Utilisation in situ et ex situ de Helix aspersa comme bioindicateur de la contamination des sols par le cadmium et le plomb.

Abstract

The worrying environmental situation in Algeria today is the result of the irresponsible use of non-renewable resources to meet the excessive needs of industry and agriculture over the past century, several persistent pollutants were released and then accumulated in the different ecosystems. Trace metal elements are classified as one of the most dangerous pollutants due to their high toxicity and persistence in the environment. This study was conducted to assess the state and quality of contaminated soils with metals by the use of the snail Helix aspersa (syn. Cantareus aspersus or Cornu aspersum O.F. Müller, 1774) as a bioindicator via ex situ and in situ ecotoxicity tests. Indeed, two ex situ tests were performed to determine a dose-response relationship between Pb or Cd concentrations in soils and the growth of weight and shell diameter of H.aspersa species according to the recommendations of ISO 15952 (2006).In addition, six ex situ tests were conducted to assess the influence of soil physicochemical parameters on lead and cadmium bioavailability and toxicity to Helix aspersa. Finally, the soils of two areas with different levels of metallic contamination in North-East Algeria have been investigated via active biomonitoring (in situ test); Indeed, sub-adult populations of H. aspersa have been exposed under natural conditions to soils in two areas: B'kira - Constantine and El Hadjar Ŕ Annaba. Inhibitory concentrations of 50% of Helix aspersa growth (IC 50) were ranged between 2397-8194 µg/g for lead and 327-910 µg/g for cadmium. The physicochemical properties of the soil, including pH, CEC and OM, have a clear effect on the bioavailability and toxicity of Cd and Pb to Helix apsersa. Total metal concentrations in the soils studied were ranged from 22.27 to 635.38 µg/g for lead and 0.13 to 0.53 µg/g for cadmium. The species H. aspersa showed a higher accumulation capacity for Cd than for Pb. This study confirms the high performance of Helix aspersa in the ecological risk assessment for contaminated soils with metals.