Alain Ploquin

Wild Brown Trout Affected by Historical Mining in the Cévennes National Park, France

In the protected area of the Cévennes National Park (Southern France), 114 wild brown trout (Salmo trutta fario) were captured at six locations affected to different extents by historical mining and metallurgy dating from the Iron Age to Modern Times. Cadmium and lead in trout livers and muscles reflect high sediment contamination, although an age-related effect was also detected for hepatic metal concentrations. Lead isotope signatures confirm exposure to drainage from mining and metallurgical waste. Developmental instability, assessed by fluctuating asymmetry, is significantly correlated with cadmium and lead concentrations in trout tissues, suggesting that local contamination may have affected fish development. Nowadays, the area is among the least industrialized in France. However, our results show that 60% of the specimens at one site exceed EU maximum allowed cadmium or lead concentration in foodstuffs. The mining heritage should not be neglected when establishing strategies for long-term environmental management.

Helium trapped in historical slags: a search for temporal variation of the He isotopic composition of air

In an attempt to investigate short-term variations of the isotopic composition of atmospheric helium, we have analyzed He isotopic ratios of gases trapped in metallurgical slags from France and United Arab Emirates covering the historical period 900–1991 AD. These slags have been produced in blast- and shaft-furnaces, which are characterized by different temperatures (∼1300°C and ∼1600°C, respectively) and ventilation conditions (open air and compressed air, respectively). The slags contain 100–500 μm vesicles believed to contain air trapped at the epoch of processing. Results for shaft-furnace slags indicate that the melts were not fully equilibrated with atmospheric helium. Crush-extracted He from blast-furnace samples indicate better homogeneity and, in the case of a He-rich sample processed in 1500 AD, show the occurrence of a He component presenting a 3He excess of 3.6±1.2% relative to the isotopic composition of atmospheric helium sampled in 1995. Among possible sources and sinks of He isotopes, the release of crustal, 4He-rich, helium as the result of anthropogenic activity, mainly hydrocarbon exploitation, is consistent with a temporal change of the He isotopic composition of air between the 16th century and the present-day. The present-day rate of change of the atmospheric He isotopic ratio is estimated to be −0.014±0.007%/yr.

L'altération naturelle des scories de la métallurgie ancienne : un analogue de déchets vitrifiés

The study of the natural alteration of ancient vitreous slags (100 to 4 000 years) suggests a single global mechanism. In a first stage, weathering consists of a selective extraction of the modifier cations of glass (including Pb and Ba). This phenomenon is associated with an increase of the solution pH, inducing the glass dissolution. The elements with a weak limit of solubility remain in place and can form hydroxides (Al, Fe). Pb and Ba are extracted from weathered glass. Pb is located in Fe-hydroxides, Ba may form sulfides. The rate of alteration varies from 20 to 180 μm per 1 000 years.