A new approach to understand methylmercury (CH3Hg) sources and transformation pathways: Compound-specific carbon stable isotope analysis by GC-C-IRMS

Monday, 14 December 2015
Poster Hall (Moscone South)
Pascale Anabelle Baya1, David Point1, David P Amouroux2, Benoit Lebreton3 and Gael Guillou3, (1)Géosciences Environnement Toulouse (GET), UMR CNRS / IRD / Université Paul Sabatier, Toulouse, France, (2)IPREM / CNRS, Pau, France, (3)Littoral, Environnement et Sociétés (LIENSs), UMR 7266 CNRS‐Université de La Rochelle, Institut du Littoral et de l’Environnement, La Rochelle, France
Methylmercury (CH3Hg) is a potent neurotoxin which is readily assimilated by organisms and bio-accumulates in aquatic food webs. In humans, consumption of CH3Hg contaminated marine fish is the major route of mercury exposure. However, our understanding of CH3Hg transformation pathways is still incomplete. To close this knowledge gap, we propose to explore the stable carbon isotopic composition (δ13C) of the methyl group of CH3Hg for a better understanding of its sources and transformation mechanisms. The method developed for the determination of the δ13C value of CH3Hg in biological samples involves (i) CH3Hg selective extraction, (ii) derivatization, and (iii) separation by gas chromatography (GC) prior to analysis by combustion isotope ratio mass spectrometry (C-IRMS). We present the figures of merit of this novel method and the first δ13C signatures for certified materials (ERM-CE464, BCR414) and biological samples at different marine trophic levels (i.e., tuna fish, zooplankton). The implications of this new approach to trace the pathways associated with Hg methylation and the mechanisms involved will be discussed.