Snail watch to survey the transfer of PCB and PCDD/F on a polluted site converted into a photovoltaic power plant

In 2008, a fire on a former industrial site in Saint Cyprien (France) caused a severe contamination with persistent organic pollutants (POP) to surrounding soils. About 14 hectares of pasture were consequently forbidden to agricultural use. To give a new usage to this site, a power plant was built in 2010 by Luxel SAS. This installation produces green electricity since early October 2013 and constitutes a pilot site for research on POP toxicity and degradation processes over time with bioindicators. The objective of the research program TROPE (Transfer and Risk of Organic PErsistent pollutants for snails) was to assess, thanks to active biomonitoring, the bioavailability of PCBi, PCB-DL and PCDD/F to a soil invertebrate living at the soil surface, the ubiquitous land snail, Cantareus aspersus. Snails were caged for 28 days on 4 grassy plots with increasing POP contamination (3631 to 34942 ng.kg-1 dw for ?7 PCBi, 2 to 222 ng TEQOMS2005.kg-1 dw for ?17 PCDD/F and 1.15 to 22.8 ng TEQOMS2005.kg-1 dw for ?12 PCB-DL. An additional plot highly contaminated (>400 mg.kg-1 PCBi and sum PCDD/F + PCB-DL > 20,000 ng TEQ.kg-1) located near the studied site was also studied. Internal residues in the soft body of snails for the sum of the ?7 PCBi were from 556 to 462,124 ng.kg-1 fw whereas the ?17 congeners of PCDD/F varied from 0.052 to 1.18 ng TEQ .kg-1 and for the ?12 PCB-DL from 0.064 to 72 ngTEQ.kg-1. The ratio PCDD/F / PCB-DL was from 1 to 2.6 and the ratio PCBi/PCB-DL from 4252 to 8689. Among the PCBi, congeners 101, 138 and 153 were the most accumulated pollutants. For PCB-DL, PCB105 and 118 were the most abundant whereas for the PCDD, OCDD and HpCDD were predominant in the snail tissues. Results showed that POP are bioavailable for snails and may reach high internal body concentration in highly contaminated plots. This study provides first data on the capability of land snails to accumulate various PCB, PCB-DL and PCDD/F and reveals that these soil invertebrates may be a source of POP exposure to their consumers. Two other campaigns of biomonitoring are planned in the coming years to assess the evolution of bioavailability of POP on this polluted area, unsuitable for agricultural purposes, but that has recovered an industrial value. These studies will help to sharpen our understanding of the PCB impact on the ecosystems