A revised chronology for the Grotte Vaufrey (Dordogne, France) based on TT-OSL dating of sedimentary quartz.

Grotte Vaufrey, located in the Dordogne region of southwestern France, is well known for its substantial archaeological sequence containing a succession of Acheulean and Mousterian occupations. While over the last thirty years numerous studies have attempted to outline a detailed chronostratigraphy for this important sequence, the failure to employ a common chronological framework has complicated its interpretation. Here, we aim to resolve these inconsistencies by providing a new chronology for the site based on luminescence dating. To this end, thermally-transferred optically stimulated luminescence (TT-OSL) dates were obtained from eight sediment samples distributed throughout the sequence, which, when combined with already available chronological information, produce a new chronostratigraphic model for the site. Our results demonstrate that the Typical Mousterian extends from MIS 7 to MIS 5, while the earliest Acheulean occupation could be associated with MIS 8 and may date to as early as MIS 10. When compared with other regional sequences, the Acheulean levels from the Grotte Vaufrey provide evidence for one of the earliest hominin occupations in southwestern France.

Different methods in TiO2 photodegradation mechanism studies: gaseous and TiO2-adsorbed phases.

The development of photocatalysis processes offers a significant number of perspectives especially in gaseous phase depollution. It is proved that the photo-oxidizing properties of photocatalyst (TiO(2)) activated by UV plays an important role in the degradation of volatile organic compounds (VOC). Heterogeneous photocatalysis is based on the absorption of UV radiations by TiO(2). This phenomenon leads to the degradation and the oxidation of the compounds, according to a mechanism that associates the pollutant's adsorption on the photocatalyst and radical degradation reactions. The main objective of the study is the understanding of the TiO(2)-photocatalysis phenomenon including gaseous and adsorbed phase mechanisms. Results obtained with three different apparatus are compared; gaseous phases are analysed and mechanisms at the gaseous phase/photocatalyst interface are identified. This study leads to improve understanding of various mechanisms during pollutant photodegradation: adsorption of pollutants on TiO(2) first takes place, then desorption and/or photodegradation, and finally, desorption of degradation products on TiO(2). The association of analytical methods and different processes makes the determination of all parameters that affect the photocatalytic process possible. Mastering these parameters is fundamental for the design and construction of industrial size reactors that aim to purify the atmosphere.