Mercury in air and plant specimens in herbaria: A pilot study at the MAF Herbarium in Madrid (Spain)

Abstract

We present data from a study of mercury concentrations in air and plant specimens from the MAF Herbarium in Madrid (Spain). Hg (gas) emissions from old plant collections treated with mercuric chloride (HgCl(2)) in herbaria may pose a health risk for staff working in installations of this type. This is an issue not yet properly addressed. Plants that underwent insecticide treatment with HgCl(2) at the MAF Herbarium until the mid 1970s have persistent high concentrations of Hg in the range 1093-11,967 microg g(-1), whereas untreated specimens are in the range of 1.2-4.3 microg g(-1). The first group induces high concentrations of Hg (gas) in the main herbarium room, with seasonal variations of 404-727 ng m(-3) (late winter) and 748-7797 ng m(-3) (early summer) (baseline for Hg: 8 ng m(-3)). A test survey at another herbarium in Madrid showed even higher concentrations of Hg (gas) above 40,000 ng m(-3). The World Health Organization guidelines for chronic exposure to Hg (gas) are estimated at a maximum of 1000 ng m(-3). While staff was aware of the existence of HgCl(2) treated plants (the plant specimen sheets are labelled as 'poisoned'), they had no knowledge of the presence of high Hg (gas) concentrations in the buildings, a situation that may be relatively common in herbaria.

Mercury fluxes and pools in three subtropical forested catchments, southwest China

“…Application RA-915þ analyzer with a multi-path analytical cell attached the RP-91 (cold vapor) and PYRO-91 (pyrolysis) accessories allow to analyze Hg in liquid and solid samples, and some authors have successfully used these methods for measuring Hg concentrations in water (Esbrí and Higueras, 2005;Higuerasa et al, 2006;Won et al, 2007) and solid (Chen et al, 2001;Oyarzun et al, 2007;Rodriguez et al, 2007;Shuvaeva et al, 2008) samples. In this study, the precision, obtained from eight replicate determinations of certificated reference material, was 3.0% for diluted (10 ng L À1 )…”

The effect of mercuric chloride treatment as biocide for herbaria on the indoor air quality

“…Based on surveys it has become clear that different methods were applied [7], for example by soaking or brushing materials using a solution of HgCl 2 with ethanol. Herbarium samples can continue to emit metallic mercury many decades after their last treatment with mercuric chloride [5,[8][9][10][11].…”

“…In the Netherlands (National Herbarium collection repositories, now dismounted) steady sate concentrations in the indoor were found to be over 10 µg Hg/m 3 while for example other collections were causing concentrations of mercury indoor of about 25 µg Hg/m 3 (Cambridge herbarium) and 40 µg Hg/m 3 (MAF, Madrid). However, opening collection boxes or cabinets where specimens are stored can cause a peak concentration of 50 µg Hg/m 3 and higher [5,[8][9][10][11]. Different mechanisms can be hypothesised as responsible for the emission of mercury from herbarium collections.…”

Évaluation de la toxicité des spécimens naturalisés

“…Cette perspective trouve écho dans le domaine muséal où la détection des résidus toxiques fait l'objet d'une attention accrue en raison des problèmes moraux et juridiques qu'elle soulève. Des premières investigations ont été réalisées dans les collections ethnographiques (Boulton, A., 1986 ;Odegaard et al, 2005), les herbiers (Oyarzun, 2007) mais plus rarement dans les collections de spéci-mens naturalisés (Sirois, 2001). …”