5:15 PM - 6:45 PM
[MAG33-P10] Gold folding screen (Western gold leaf) dissolved by the "Black Rain" caused by the atomic bombing of Hiroshima
Keywords:Black Rain, Acid rain, Gold folding screen, Western gold leaf, Copper sulfate hydrate
[Introduction]
Although studies of the "Black Rain" itself have been conducted, along with surveys and research reports on estimating the rainfall area of the "black rain" that occurred after the atomic bombings of Hiroshima and Nagasaki in 1945, these studies have been conducted mainly from the viewpoint of radioactive materials, and no studies on the major components of the rain itself have been found, except for a study on soot (Fields DE, 1989[1]). In 2022, a gold folding screen (western gold leaf) with traces of the "Black Rain" was newly discovered, and together with the curatorial staff of Hiroshima Peace Memorial Museum, we investigated, collected, and analyzed it. As a result, we were able to get closer to the essence of the "Black Rain.
[Samples]
One control and three black traces of gold (western gold leaf) folding screens were cut and used as samples.
[Methods and Results]
The "Black Rain" traces were observed by changing the light path of an optical microscope up and down, and as a result, the western gold leaf (copper alloy containing zinc) in the black traces disappeared and light penetrated from below (Figures 1 and 2). The SEM/EDX analysis of the metallic foil pieces left in the black traces indicated that nitrogen (N) and sulfur (S), two of the elements in the black material, dissolved copper (Cu) in the western gold leaf foil, suggesting the presence of nitric acid (N) and sulfuric acid (S). Results of XRD analysis of the black traces showed copper sulfate hydrate (presumed), but no copper nitric acid compounds were detected. Based on the results of the sulfuric acid and nitric acid corrosion simulation experiments using the model western gold leaf screen piece, it is highly likely that the "Black Rain" was more acidic than pH 3.
References: [1] Fields DE, Cole LL, Summers S, Yalcintas MG, Vaughan GL. Generation of aerosols by urban fire storm. Aerosol Sci Technol 10:28 –36; 1989.
Acknowledgments: This study was funded by the Ministry of Health, Labour and Welfare of Japan. We would like to express our deepest gratitude to the staff of Hiroshima Peace Memorial Museum, especially the curatorial staff, the bereaved families who donated valuable artifacts, Rekiseisha, Inc. for providing samples of the model folding screens, Dr. Tatsuya Katsuno of the Electron Microscope Laboratory(Dissection Center), Graduate School of Medicine, Kyoto University, Dr. Takuo Okuchi of our institute, and Osaka Research Institute of Industrial Science and Technology for their assistance in the analysis of the artifacts.
Although studies of the "Black Rain" itself have been conducted, along with surveys and research reports on estimating the rainfall area of the "black rain" that occurred after the atomic bombings of Hiroshima and Nagasaki in 1945, these studies have been conducted mainly from the viewpoint of radioactive materials, and no studies on the major components of the rain itself have been found, except for a study on soot (Fields DE, 1989[1]). In 2022, a gold folding screen (western gold leaf) with traces of the "Black Rain" was newly discovered, and together with the curatorial staff of Hiroshima Peace Memorial Museum, we investigated, collected, and analyzed it. As a result, we were able to get closer to the essence of the "Black Rain.
[Samples]
One control and three black traces of gold (western gold leaf) folding screens were cut and used as samples.
[Methods and Results]
The "Black Rain" traces were observed by changing the light path of an optical microscope up and down, and as a result, the western gold leaf (copper alloy containing zinc) in the black traces disappeared and light penetrated from below (Figures 1 and 2). The SEM/EDX analysis of the metallic foil pieces left in the black traces indicated that nitrogen (N) and sulfur (S), two of the elements in the black material, dissolved copper (Cu) in the western gold leaf foil, suggesting the presence of nitric acid (N) and sulfuric acid (S). Results of XRD analysis of the black traces showed copper sulfate hydrate (presumed), but no copper nitric acid compounds were detected. Based on the results of the sulfuric acid and nitric acid corrosion simulation experiments using the model western gold leaf screen piece, it is highly likely that the "Black Rain" was more acidic than pH 3.
References: [1] Fields DE, Cole LL, Summers S, Yalcintas MG, Vaughan GL. Generation of aerosols by urban fire storm. Aerosol Sci Technol 10:28 –36; 1989.
Acknowledgments: This study was funded by the Ministry of Health, Labour and Welfare of Japan. We would like to express our deepest gratitude to the staff of Hiroshima Peace Memorial Museum, especially the curatorial staff, the bereaved families who donated valuable artifacts, Rekiseisha, Inc. for providing samples of the model folding screens, Dr. Tatsuya Katsuno of the Electron Microscope Laboratory(Dissection Center), Graduate School of Medicine, Kyoto University, Dr. Takuo Okuchi of our institute, and Osaka Research Institute of Industrial Science and Technology for their assistance in the analysis of the artifacts.