Monitoring mercury in two South African herbaria

Abstract Mercury [Hg] emissions from old plant collections treated with mercuric chloride (HgCl2) may present a high health risk for staff working in certain herbaria. The present study evaluated Hg concentrations in ambient air, plant specimens and biological samples from staff working in the Pretoria National Herbarium (PRE) and the H.G.W.J. Schweickerdt Herbarium (PRU), University of Pretoria. Biological samples from a group of 15 people exposed to HgCl2 in herbaria and a non-exposed control group of five people were studied. Additionally, plant samples from herbarium specimens treated and non-treated with HgCl2 were analysed. Plant materials treated with HgCl2 had persistent high concentrations of Hg in the range of 114–432 μg g−1, whereas untreated materials were in the range of 0.20–0.45 μg g−1. The HgCl2- treated plant specimens induced elevated concentrations of Hg into the herbarium rooms near storage cabinets, where up to 1 μg m−3 of Hg was measured in the air of both herbaria. However, no significant difference in mean Hg concentrations in hair was found between herbarium workers and members of the control group, 0.46 and 0.64 μg g−1 respectively (p