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Combined effects of gamma-irradiation, dose rate and mycobiota activity on cultural heritage – Study on model paper

(Assessment of optimal irradiation conditions for gamma-radiation treatment of common fungi on selected cultural heritage objects) Marušić, Katarina; Šegvić Klarić, Maja; Sinčić, Lucija; Pucić, Irina; Mihaljević, Branka (2019) Combined effects of gamma-irradiation, dose rate and mycobiota activity on cultural heritage – Study on model paper. Radiation Physics and Chemistry, 170 . ISSN 0969-806X

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Abstract

Cellulose, the main constituent of paper-made objects of cultural heritage (CH), is a favorable substrate for fungal growth. Gamma irradiation is a well-established low-cost treatment convenient for decontamination of such objects. Since side-effects to paper-based CH are always a concern the aim of this work was to investigate if a synergism of microbiological contamination and gamma irradiation effects exists and if it induces changes in paper's appearance and structure. The dose rate plays an important yet generally neglected role in the efficacy of the radiation treatment so another goal was to assert its influence on decontamination efficiency and paper properties. Irradiation conditions for treating the highly resistant secondary colonizer Cladosporium sphaerospermum, as well as the naturally occurring mycobiota were evaluated. Untreated and inoculated samples of paper were irradiated with doses commonly applied to CH objects, as well as to significantly higher doses, at two dose rates that differ for two orders of magnitude. Microbiological analysis of irradiated samples was conducted. Colorimetric analysis, UV-vis and FTIR measurements were performed after short lived reaction species have decayed. The results have shown that in the case of high contaminations (104 CFU/g) the applied dose needs to be adjusted and that the corresponding dose rate needs to be high enough. While at the dose rate of 31 kGy/h the irradiation dose of 7 kGy seems to be effective to obtain proper reduction of mycobita, at the dose rate that was two orders of magnitude lower the required dose increased approximately ten times. Thus the reevaluation of the recommended dose of 8 ± 2 kGy is needed. Considering the side effects of radiation treatment the dose rate effect has also been observed. At the higher of the investigated dose rates the irradiation doses needed for decontamination did not alter the appearance of paper, while at the lower one the changes were hardly perceptible. The main species showing their contribution to color change were the carbonate anion-radicals that were formed on the CaCO3 paper filler. No oxidation or change in crystallinity of cellulose was detected. Overall changes were too insignificant to make any conclusion on the contribution of mycobiota to the irradiation side-effects on the paper under the studied conditions.

Item Type: Article
Additional Information: This work was supported by IAEA Coordinated Research Project F23032, entitled "Developing Radiation Treatment Methodologies and New Resin Formulations for Consolidation and Preservation of Archived Materials and Cultural Heritage Artefacts" (2015-2020).
Uncontrolled Keywords: Cladosporium sphaerospermum; Radiation treatment; D10 value; CIE Lab colorimetry; FTIR; Carbonate anion-radical
Subjects: NATURAL SCIENCES > Chemistry
NATURAL SCIENCES > Chemistry > Applied Chemistry
NATURAL SCIENCES > Biology > Microbiology
NATURAL SCIENCES > Interdisciplinary Natural Sciences
NATURAL SCIENCES > Interdisciplinary Natural Sciences > Radiation Science
FIELD OF ART > Interdisciplinary Fields of Art
Divisions: Division of Materials Chemistry
Projects:
Project titleProject leaderProject codeProject type
IAEA Coordinated research project "Assessment of optimal irradiation conditions for gamma-radiation treatment of common fungi on selected cultural heritage objects"Branka Mihaljević and Katarina Marušić18960Coordinated Research Project
Depositing User: Katarina Marušić
Date Deposited: 05 May 2020 10:20
Last Modified: 05 May 2020 10:24
URI: http://fulir.irb.hr/id/eprint/5724
DOI: 10.1016/j.radphyschem.2019.108641

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