Mercury speciation in herbaria as a tool for collections' restoration and health hazard mitigation

Botanical collections (herbaria) are unique archives for botanical research, which help preserve plant genetic resources and biodiversity. Mercuric chloride (HgCl2) was widely employed to botanical specimens to prevent samples’ degradation [1]. Over time, HgCl2 decomposes to Hg0, which readily vaporizes, becoming a serious occupational health hazard for the workers and visitors of worldwide collections [2-5]. The present project aims at investigating Hg-contaminated botanical collections of the Erbario Centrale Italiano of the Natural History Museum of the University of Firenze (Italy) by non-destructive techniques, such High Resolution X-ray Absorption Near Edge Spectroscopy (HR-XANES). The proposed experiment will reveal the Hg speciation in the botanical samples, the paper supports, and the wooden storage cabinets, offering specific information to set-up restoration methods, combining mitigation of the potential Hg exposures to humans with preservation of sample integrity.