Archaeological excavation site of Wuwangdun Tomb in Huainan, Anhui. Photographed by Huang Bohan, reporter of Xinhua News Agency

"At present, 443 outer coffin covers and 78 bamboo mats covered by them have been successfully extracted, and the moisture and mold protection work of outer coffin covers and bamboo mats has been carried out; a large number of bronzes and lacquered wooden relics have been extracted..." On April 16, the State Administration of Cultural Heritage held a meeting on the important progress of the "Archaeological China" major project, and released the archaeological excavation progress of the tomb of Wuwangdun in Huainan, Anhui.

The abundant archaeological achievements of the tomb of King Wu Dun have attracted attention at home and abroad. At the same time, the archaeological excavation of Wuwangdun Tomb promoted multidisciplinary and multi platform cooperation, and the use of new tools provided by science and technology was also remarkable.

——Editor

In April, the weather in Huainan City, Anhui Province, was sunny and rainy from time to time. The humid air was full of information about the germination of everything. Adjacent to Shungengshan in the north, open flat land in the south, and Wabu Lake in the west, it is located at the archaeological site of Tomb 1, Wuwangdun, Xuwa Village, Sanhe Town, Huainan. Archaeologists are busy in a tense and orderly manner.

As this large high-grade tomb of the State of Chu with the largest scale, the highest level and the most complex structure has gradually revealed its true appearance, the Chu culture has become more vivid.

High level layout, paving the "long road"

Since the official launch of the archaeological excavation of Wuwangdun in 2020, a cultural relics protection team consisting of experts from multiple institutions and disciplines has been established immediately. At the same time, a series of supporting facilities for archaeological excavation, such as the main tomb protection shed, cultural relics warehouse and archaeological laboratory, have also been completed rapidly.

Plan before you act. Zhang Zhiguo, the research librarian of the Archaeological Research Center of the State Administration of Cultural Heritage and the cultural relics protection director of the archaeological excavation project of Wuwangdun Tomb, introduced that before the commencement of archaeological excavation, according to the types of cultural relics unearthed from tombs of similar times, the cultural relics unearthed from Tomb No. 1 of Wuwangdun were predicted, and on this basis, a plan for on-site protection and multidisciplinary research of unearthed cultural relics was formed.

One of the biggest problems soon came to everyone. Because the cultural relics inside the outer coffin are immersed in water all the year round, and the outer coffin cover and bamboo mat above the water surface are also in a state of saturation, how to carry out timely emergency protection for the unearthed cultural relics?

"The archaeological excavation of Wuwangdun Tomb is very different from Sanxingdui. Sanxingdui archaeological excavation is in a relatively stable environment and can be extracted slowly, but not Wuwangdun Tomb," said Gong Decai, a professor at the University of Science and Technology of China, "The tomb of Wuwangdun has been immersed in water for a long time. Once it is out of a saturated environment and in direct contact with oxygen, the wooden figurines, lacquerware and other cultural relics will soon curl, warp, change color, and even shrink and deform significantly. We need to extract cultural relics as soon as possible and send them to the laboratory as soon as possible while preserving as much information about cultural relics as possible."

The grave pit is square, and there is a slope tomb path to the east of the grave pit. The four walls of the grave pit have 21 steps that are gradually inward. Under the layers of compacted earth, a nine room outer coffin appeared in front of the archaeologists. The huge bamboo mat is covered on the outer coffin cover plate, and under the bamboo mat, square wood and thin board are alternately arranged to form multi-layer protection. Zhang Zhiguo said that the layout of Tomb 1 at Wuwangdun was gradually clear by using the high-density resistivity method. The wooden outer chamber adopts a "sub" shape structure, with 9 rooms in total. This is the first time to see a clearly structured nine room Chu tomb in China.

Bamboo mats quickly entered the protection scope of the archaeological team. Zhang Wenjie, a professor at the School of History and Cultural Heritage of Xiamen University, recalled that after the excavation, the first thing that came into view was the bamboo mat laid on the outer coffin cover. "Although more than 2000 years have passed, bamboo mats in some areas can still show yellow color."

Decadent, incomplete, cracked and thousands of years of underground life have made most bamboo mats fragile.

How to carry out temporary reinforcement and emergency protection for bamboo mat safely and efficiently? Menthol temporary solid technology provides a solution. This pioneering achievement, invented by Professor Luo Hongjie of Shanghai University and with independent intellectual property rights in China, is an international initiative. Menthol can pre strengthen the fragile cultural relics to ensure that the cultural relics can be safely transferred to the laboratory. "And this material has no residue after natural volatilization in the air," said Zhang Zhiguo.

However, new problems follow. The environment of Wuwangdun Tomb is humid. If menthol is allowed to volatilize naturally after the bamboo mat enters the laboratory, the water in the bamboo mat will also evaporate rapidly, leading to the warping and cracking of the saturated bamboo mat. After repeated experiments, Zhang Zhiguo found that by adding alcohol, heating and other methods, menthol can be effectively removed, and the bamboo mat can be ensured in a saturated state, which not only ensures the safety of cultural relics, but also facilitates a series of protective treatments such as pollutant cleaning, iron removal, reinforcement, drying and shaping.

The largest area of ancient bamboo mat extraction work carried out at home and abroad at present has quickly achieved results. The archaeological team took the method of extracting bamboo mats in strips, with the longest bamboo mat of about 7.5 meters and the total area of more than 200 square meters, forming a technical method system for on-site reinforcement and extraction, packaging and transportation, and indoor stability protection of bamboo mats.

Classify "rescue" and still need "suit the remedy to the case"

Characters are the most mysterious symbols in history, which witness the changes of time and tell the ancient stories and magnificent legends of the land of Chu more than 2000 years ago. However, the discovery of words is not as easy as expected.

Infrared camera technology can clearly reveal the text hidden on the black outer coffin cover. To Zhang Zhiguo's delight, more than 100 words and nearly 1000 characters of ink script have been found and collected on the cover plate of the outer chamber of No. 1 tomb at Wuwangdun, which is a typical Chu script. Based on the textual content and the archaeological situation, the location and order of the outer coffin cover plate, the functional division of the outer coffin room and other contents are of great significance to the study of the construction process of the Chu tombs, the official system, the names and titles of objects and other issues.

The outer cover plate protection is also of great significance. Gong Decai said that with the gradual exposure of the outer coffin cover, the outer coffin cover was saturated with water by spraying water, covering plastic film, non-woven fabric and other measures, so as to reduce the cracking and deformation of the outer coffin cover caused by rapid evaporation of water. "In the process of extracting the outer coffin cover plate, the fragile and cracked parts are reinforced by menthol, gypsum bandages, splints and other reinforcement materials, and the stressed parts are cushioned and supported by pearl wool, bubble film and other materials, so as to reduce the damage to cultural relics during lifting and ensure the smooth development of archaeological excavation and research."

Zhang Zhiguo handled the ink script of the outer coffin cover very carefully. "We use a reversible rosin alcohol solution to seal the ink book to prevent the ink book from being damaged during the extraction, transportation and storage of the outer shell cover." Zhang Zhiguo said that after the outer shell cover cultural relics were transported to the storage site, the wood should be treated with bacteriostasis, mildew prevention and moisture preservation in a timely manner, and the growth of mold and water saturation of the outer shell cover should be monitored, The outer cover plate can be safely and stably stored and protected.

"Everything is painted." During the Spring and Autumn Period and the Warring States Period, the State of Chu has developed a very high technology for making lacquer and wood products. Many lacquered wood wares unearthed this time, including wooden figurines, lacquerware, tomb animals, etc., are lying quietly in the archaeological laboratory not far from the archaeological excavation site. In the archaeological laboratory, the reporter saw pieces of lacquer ware with gorgeous patterns and excellent workmanship being soaked in water. "This is deionized water, just like a bath, which can clean people," said Zhang Wenjie.

"The on-site protection process of lacquer woodwork mainly includes trace information collection and cleaning treatment," said Zhang Zhiguo. If there are processes such as gilding and lead tracing on the surface of lacquered wood, according to the preservation condition of color painting, it can be properly reinforced before immersion in water. "

"After cleaning, the cultural relics will be dehydrated, that is, they will be soaked in a special chemical liquid, so that the liquid can be 'melted' into the cultural relics, replacing water to support the pore structure of the wood." Gong Decai said that this set of "treatment course" is China's original glyoxal method, from Mawangdui to Marquis Yi's Tomb, from Dingtao Han Tomb to today's Wuwangdun Tomb, Tens of thousands of lacquered wood wares, under this "treatment", draw the utensils to life and glow with new vitality.

The analysis and research on some of the unearthed lacquerware shows that the lacquer used in the unearthed lacquerware from Tomb 1 of Wuwangdun is Chinese lacquer, and the paint pigments are different. The vermilion paint pigment is vermilion, the red brown paint pigment is iron red, the black paint pigment is carbon black, and the yellow color pigment is a mixture of orpiment and realgar. Some lacquerware has a gold painting technique in the decorative patterns.

Technology enabling, multidisciplinary and multi platform cooperation

When the bronze chimes sounded the clanking end of thousands of years ago, the dancers in train danced with the drums and the piano... More than 2000 years later, a sleeping Chu "band" was awakened again. When the archaeologists extracted the figurines from the mud in the outer chamber, the clothes and silk attached to them were also extracted. Zhou Yang, deputy curator of the China Silk Museum, said that silk is organic and difficult to preserve. The silk unearthed in saturated water is in a state of rottenness like wonton skin. However, "wonton skin" contains a large number of silk relics and related occurrence information.

"For the protection of archaeological silk unearthed in the humid environment in the south, the process from saturation to dryness is a matter of life and death," Zhou Yang said. The cultural protection team composed of the China Silk Museum is responsible for the emergency rescue of the unearthed silk.

Silk needs to be moisturized during emergency protection, but excessive water flow will change the state of textiles on the "dressed figurines". Faced with a dilemma, the cultural protection personnel chose to spray water for moisturizing and film wrapping. In order to increase the strength of silk, the cultural protection personnel used the method of silk protein reinforcement to "stitch" the broken molecular bonds of silk from the molecular level. "Since silk protein is the main component of silk, this homologous reinforcement method can effectively avoid the damage to cultural relics caused by the subsequent degradation of reinforcement materials, which is also our original method," said Zhou Yang.

During the excavation, Zhang Zhiguo also recorded such a critical moment. "After opening the outer coffin cover, there was water below, but dozens of plants of different sizes were floating on the water surface of the East Room 1. After salvaging it, preliminary analysis showed that it contained plums, plums, chestnuts, sweet melon seeds, lotus seeds and other fruits, as well as rice, millet, millet and other crops. It was initially determined that the tomb owner should be buried in summer or autumn when the plants were mature." Zhang Zhiguo said.

Animal and plant archaeology is an important part of modern archaeology, as well as a concentrated reflection of the interdisciplinary integration of contemporary archaeology. By means of animal and plant composition analysis, protein analysis, bone age detection and other means, archaeologists can accurately locate the age and identity information of cultural relics, and distribute "identity cards" to these elderly "underground residents". Zhang Zhiguo said that now, these plants are being sealed in plastic film and temporarily stored in the hypoxia sterilization warehouse of the archaeological laboratory, waiting for batch sorting and research.

The grain rain has passed, and the beginning of summer is coming. As the weather gets hot day by day, the environment of the tomb will change greatly. This is an extremely severe test for the cultural relics and archaeologists on the scene.

In order to create a relatively stable environment for cultural relics that are still waiting for treatment, the project team is preparing to build a "three control system" for the tomb. Zhang Zhiguo explained that "three controls" are temperature control, humidity control and oxygen control. "We are about to carry out the construction of the atomizing spray system, which will greatly reduce the workload of manual humidification of the staff. By regularly spraying the ice water mixture, not only the indoor temperature can be reduced, but also its humidity can be effectively increased; by filling the outer chamber with nitrogen, the oxygen content of the air in the outer chamber can be reduced by 50%, effectively delaying the oxidation rate of cultural relics; By controlling the environment of the archaeological site, we try our best to retain more original information, and also win valuable time for archaeological excavation. " Zhang Zhiguo said.

Gong Decai said that in the process of archaeological excavation, they used new tools provided by science and technology through multidisciplinary and multi platform cooperation to enhance their ability to find and analyze archaeological work in Tomb 1 of Wuwangdun, and improve their ability to protect historical and cultural heritage.

Guan Qiang, the deputy director of the State Administration of Cultural Heritage, said that in the next step, we should continue to strengthen archaeology and research, and in accordance with the work idea of "great archaeology", we should simultaneously promote scientific and technological dating, residue analysis, metallurgy, environment, animals and plants and other scientific and technological archaeology, and make full use of modern scientific and technological means to extract all kinds of information to the maximum extent; Establish multidisciplinary cooperation teams in archaeology, history, architecture, ancient philology, etc., deeply demonstrate the age and nature of the tomb of King Wu Dun, multi-dimensional interpretation of important issues such as the etiquette system, handicraft industry, and history of science and technology of the State of Chu, and at the same time, comprehensively promote the extraction and protection of unearthed bronzes, bamboo and wood lacquerware, silk, and related fragile and weak cultural relics, Ensure that the unearthed cultural relics are properly protected at the first time. Continue to monitor the stability and groundwater level of the graves and outer chambers, implement support and reinforcement measures, strengthen the management of archaeological site personnel, and ensure the safety of the archaeological site.                 

People's Daily (April 28, 2024, edition 06)

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