Use of biogenic and abiotic elemental selenium nanospheres to sequester elemental mercury released from mercury contaminated museum specimens
2011
Fellowes, J.W. | Pattrick, R.A.D. | Green, D.I. | Dent, A. | Lloyd, J.R. | Pearce, C.I.
Mercuric chloride solutions have historically been used as pesticides to prevent bacterial, fungal and insect degradation of herbarium specimens. The University of Manchester museum herbarium contains over a million specimens from numerous collections, many preserved using HgCl₂ and its transformation to Hgᵥ ⁰ represents a health risk to herbarium staff. Elevated mercury concentrations in work areas (∼1.7μgm⁻³) are below advised safe levels (<25μgm⁻³) but up to 90μgm⁻³ mercury vapour was measured in specimen boxes, representing a risk when accessing the samples. Mercury vapour release correlated strongly with temperature. Mercury salts were observed on botanical specimens at concentrations up to 2.85wt% (bulk); XPS, SEM–EDS and XANES suggest the presence of residual HgCl₂ as well as cubic HgS and HgO. Bacterially derived, amorphous nanospheres of elemental selenium effectively sequestered the mercury vapour in the specimen boxes (up to 19wt%), and analysis demonstrated that the Hgᵥ ⁰ was oxidised by the selenium to form stable HgSe on the surface of the nanospheres. Biogenic Se⁰ can be used to reduce Hgᵥ ⁰ in long term, slow release environments.
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