Improved polycyclic aromatic hydrocarbons and n-alkanes determination in speleothems through cleanroom sample processing

The interest in paleoenvironmental reconstructions from biomarkers in speleothems is increasing, thanks in part to the capacity of speleothems to grow continuously and to resist post-depositional alteration. In particular, the possibility exists to link high-resolution and accurately dated fire and vegetation records with isotopic data of climatic and paleoenvironmental interactions at the local and regional scale. However, the scarcity of existing methods for the quantification of organic molecules in stalagmites, together with the issues of sample availability, contamination, and low concentrations, complicate this approach. In this work, we developed a novel method for the simultaneous determination of 18 polycyclic aromatic hydrocarbons (PAHs) and 26 n-alkanes (C10-C35) and then tested it on “clean” calcite and aragonite stalagmite samples from cave KNI-51 in the Australian tropics. The method involves subsampling by using a handheld drill, then the complete dissolution of the matrix in hydrochloric a...