Environmental impact of early Basque mining and smelting recorded in a high ash minerogenic peat deposit.

More than four metres of core, covering almost 5000 years of deposition, were collected in a high ash minerogenic peat deposit located in the High Aldudes valley (Basque country), an area well known for its mineral abundance, exploited from Roman Times at least. Although minerogenic peatlands are not generally considered as the best archives to reconstruct past atmospheric metal deposition history, lead isotopic geochemistry demonstrates the integrity of the Pb record at least within the three upper meters; that is to say over the last four millennia. Zn, Cd and Cu may have been widely redistributed either by biological cycling, advective groundwater movements, or diffusional processes. Anthropogenic lead input phases are clearly pinpointed by positive shifts in Pb/Sc ratios with concomitant sharp drops in (206)Pb/(207)Pb ratios. They are often accompanied by significant declines in tree taxa, interpreted as increasing demand for wood to supply energy for local mining and/or metallurgical operations. Periods of mining and/or smelting activity are identified during Antiquity and Modern Times, and are also confirmed by textual and field evidence. Inputs from the Rio Tinto (Southern Spain), often invoked as a major lead contributor to the European atmosphere during Roman Times, were not detected here. This remote source was probably masked by local inputs. Other mining and/or smelting phases, only suspected by archaeologists, are here identified as early as the Bronze Age. Although the durations of these phases are possibly overestimated because of detrital inputs consequent to the release of lead from polluted soils over a long period of time after major pollutant inputs, the periods at which pollution peaks occur are in good agreement with archaeological knowledge and palaeo-botanical data. The combination of geochemical and palaeo-botanical techniques with field archaeology, therefore provides a powerful tool in studying the interaction of early human societies with their environment, as regards early mining and smelting.

Influence of atmospheric pollution on the lead content of wines.

Over the last century, the atmospheric fallout of anthropogenic lead has evolved with time, as a function of the chronological variability of transient lead inputs from both industrial and gasoline origins. This variability has been mostly documented over North America and northern Europe. In this study we used ICP-MS for the determination of lead isotope ratios and showed that a series of French wines followed the evolution of the environmental lead record over the last century. We observe the same three-step chronological evolution of the lead isotopic composition, which reflects a western European signal. In the post 1950 vintages, the lead isotope composition reflects a dominant atmospheric fallout. Since approximately 1950, Pb concentrations have been much lower than before, decreasing consistently from approximately 0.25 mg l-1 around the early 1950s, down to less than approximately 0.1 mg l-1 nowadays. Reflecting the airborne pollution, the lead isotopic signature is also specific of the continental origin of the wines and lead isotope ratios determination in wines appears to be a promising tool for certifying wine authenticity.