Polycyclic Aromatic Hydrocarbons in stalagmites : Occurrence and use for analyzing past environments
Résumé
This article presents a preliminary investigation into the value of Polycyclic Aromatic Hydrocarbons (previous termPAHs)next term as markers for interpreting past environments in karst areas. We analyzed a core sample representing the last 400 years' growth from a massive stalagmite in the Chevaline Cave (Vercors, France), together with the soil overlying the karst directly above the stalagmite. During the last millennium, this area has been profoundly affected by human activities, such as slash and burn agriculture, charcoal burning and forestry. These activities may have induced changes in previous termPAHnext term production (in the soil) and thus in the previous termPAHnext term record (in the stalagmite). previous termPAHsnext term were extracted using both the Soxhlet method and the ultrasonic method in order to compare extraction yields. The ultrasonic method, in conjunction with classic HPLC/fluo analysis, was adopted for the analyses as it gave the greater yields. previous termPAHnext term distributions were obtained for the stalagmite and for the overlying soils. The sum of the previous termPAHnext term measured in the stalagmite ranges from 18 to 30 ng/g. Furthermore, the more soluble and labile previous termPAHsnext term (lighter than anthracene) dominated the previous termPAHnext term distribution in the stalagmite (about 90% of low molecular weight previous termPAH)next term. However, we did not find any obvious source fingerprints in the soil or the stalagmite, and we observed an unexpected discrepancy between the previous termPAHnext term distributions in the stalagmite and its stratigraphy, which is controlled by mineral and organic inclusions. Although previous termPAHnext term analyses can provide valuable data about the transfer of organic compounds in the karst, it is difficult to extract meaningful paleoenvironmental information from previous termPAHsnext term in stalagmites over the time scale of this study.