Application of gamma radiation for disinfection of fungi in a large volume of historical archives damaged by flood following Typhoon Hagibis 2019, Japan: A case report.

A large volume of historical archives was extensively damaged by flood water, following Typhoon Hagibis in Fukushima, Japan, in October 2019. They were rescued from the stricken area within a week, however, the prolonged exposure of paper documents to water caused severe biodegradation by fungal growth. To disinfect fungi, the paper documents were exposed to gamma radiations emitted by a source of Cobalt 60 by the industrial irradiation service. The wet paper documents were mainly contaminated with hydrophilic and cellulolytic fungi, including Trichoderma, Stachybotrys, and Fusarium; no fungi grew after irradiation. These results indicated that the average absorbed dosage from 13.1 kGy to 16.1 kGy were sufficient to disinfect paper documents heavily contaminated with fungi. In the present study, we demonstrated the successful practical use of irradiation in fungi-damaged paper documents using a commercial gamma-irradiation facility.

Thermoluminescence of coral skeletons: a high-sensitivity proxy of diagenetic alteration of aragonite.

Diagenetic alteration of aragonite coral skeletons causes changes in their chemical and isotopic compositions. Such altered coral samples are unsuitable for age dating or paleoclimate reconstructions. Recently developed microanalysis techniques have elucidated secondary aragonite precipitation and calcite overgrowth on primary aragonitic coral skeletons, but an effective screening method for bulk samples is still desirable. Although powder X-ray diffraction (XRD) analysis is widely used for this purpose, its detection limit for calcite (1-2% at best) is not sufficient to detect very small amounts of diagenetic calcite. Here, we propose that thermoluminescence (TL) spectra can be used to detect the presence of tiny amounts of secondary calcite in coral skeletons. We used a TL spectrometer with a Fourier-transform detector to detect the calcite component in TL spectra of powdered skeletons of modern and fossil corals (from 127 ka and 3.5 Ma) in which calcite was not detectable by XRD. The key element is manganese, because the TL emission efficiency and the partition coefficient of Mn are greater for calcite than for aragonite. As a result, the calcite spectral component becomes evident. Thus, the TL spectroscopic technique is a highly sensitive tool for screening fossil corals for diagenetic alteration.