Origin of Bromine in Ancient Sutras of the Otani Collection - PIXE Application to Preservation of Cultural Assets

摘要

Some small fragments of rag paper - made more than a thousand and a few hundred years ago, and excavated at Turfan, west of China by the Otani-expedition dispatched mere during the late Meiji and the Taisho eras - were measured by PIXE. Bromine was highly detected in all of these ancient fragments and modem paper samples that had been placed together with these Turfan manuscripts. In other paper samples, bromine could not be detected (H+, 4MeV, 5OjiC and Vt, 2MeV, lOOuC) and their average concentration was about l.lppm (SD=l.llppm, N=15, 0.3~3.4ppm). The bromine contamination of ancient subras is mainly caused by larvicide of methyl bromide, and tne observation suggests that the ancient manuscripts might be spoiled gradually by agricultural chemicals for protecting them from vermin.