New procedure to combat threat from mercury in museum specimens

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A safe and cheap procedure to aid the reduction of harmful levels of toxic pesticides in museums’ plant specimens has been discovered.

Historically, museums and other collectors applied pesticides to botanical materials to prevent insect and fungal damage, commonly using highly toxic compounds of mercury and arsenic. These poisons remain in the collections today, potentially causing serious health and safety concerns in museums across the world.

University of Lincoln School of Life Sciences academic Professor Belinda Colston and PhD graduate Dr Vicky Purewal have now developed an innovative and economical method to detect harmful mercury in preserved plant specimens.

They have discovered that the mount paper used to display the specimens will shine fluorescent orange under a UV lamp if mercury is present, allowing for rapid detection without the need for expensive and time-consuming laboratory testing.

Amgueddfa Cymru – National Museum Wales, where Dr Purewal is the Botanical Conservation Officer, has used the methodology to identify a number of contaminated specimen sheets in its huge collection and to prioritise which specimens required immediate re-mounting.

Dr Purewal explained: “When specimens were treated with pesticides, the mercury would run off the plant and be soaked into the backing paper. The person handling the specimen would be absorbing these contaminants through their skin. Nobody realised this was happening. Some institutions were reapplying the pesticide to prevent damage to the specimen, unaware that the mercury was accumulating on the backing sheets.”

Dr Purewal decided to investigate the issue of mercury contamination after attending a conference in which the issue was discussed.

However, spot tests on specimens did not reveal any contaminants. Dr Purewal and Prof Colston then started using UV radiation to image the specimen, and observed the fluorescent spots on the backing sheet. Research has linked these spots to the presence of mercury.

The discovery is now being used to help other organisations scan their specimens.

Dr Purewal, who recently scanned 300 specimens from the Royal College of Surgeons’ botanical collection, said: “It gives museums and collectors a really quick idea as to what they are looking at and whether collections are safe or need to be re-mounted. Taking specimens off the backing should reduce contamination 20 fold. It’s just a case of raising awareness.”

Professor Colston added: “It is hoped that this method will allow safe, standard procedures to be implemented within museums to protect personnel and visitors when handling the collections. It is a very simple and cheap technique that is accessible to even the smallest museums across the world.”

Biocides and pesticides are no longer used to protect botanical specimens; instead they go into a deep freeze of at least -20C for 3–5 days. This is not, however, a long-term solution, so cyclic freezing is necessary.

Dr Purewal completed her Conservation Science Masters at De Montfert University, Leicester, followed by a PhD under the supervision of Professor Colston at the University of Lincoln.


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Marie Daniels - PR OfficerMarie Daniels – PR Officer
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