The mystery of the mercury river in Qin Shi Huang’s tomb

Up to now, archaeologists have not been able to accurately answer the origin and use of the large amount of mercury in the tomb of Emperor Qin Shi Huang.

Theo SCMPthe mausoleum complex of Emperor Qin Shi Huang at the foot of Lishan Mountain in Xi’an City, Shaanxi Province, China, has never been opened. However, Sima Qian – a historian of the early Han Dynasty (from 206 BC to 220 AD) once described this as a large underground world with sophisticated design, simulating the starry sky above and the country below.

In the book History, Sima Qian wrote that in the tomb there were large rivers of mercury flowing automatically. For decades, archaeologists and historians used non-invasive survey methods and historical documents to assess whether surviving evidence could substantiate Sima Qian’s account.

Theo Chemistry Worldthe first detailed study of mercury concentrations in the tomb took place in the early 1980s, when experts from the Institute of Geography and Geochemistry of the China Institute of Geo-Environmental Monitoring drilled small holes into the ground over an area of ​​12,000 square meters and took soil samples for analysis. While the soil outside the central area of ​​the tomb contained an average of 30 parts per billion (ppb) of mercury, the average concentration in the soil above the tomb was 250 ppb, in some places up to 1,500 ppb. A second survey in 2003 yielded similar results: unusually high concentrations of mercury both in the soil and in moisture among the gravel.

Through a series of drill samples in previous research, the team of experts created a preliminary map and discovered that the place with the highest mercury concentration was in the northeast and south corners of the tomb, consistent with the location of the Yellow River and Yangtze River when viewed from the Qin Dynasty’s capital, Ham Duong.

According to archaeologist Qingbo Duan at Northwestern University in Xi’an, the above distribution of mercury corresponds to the location of waterways during the Qin Dynasty. However, archaeologist Yinglan Zhang of the Shaanxi History Museum does not rule out the possibility that the burial site collapsed thousands of years ago, causing mercury to evaporate into the soil for a long time, making it difficult to speculate on a direct connection with any rivers or lakes.

The survey results do not help determine the exact amount of mercury underground or the source, but Duan estimates that Qin Shi Huang’s tomb may contain at least 100 tons of the metal. Experts believe that the mercury layer can create a toxic environment, help prevent microorganisms from decomposing bodies, prevent corrosion and repel grave robbers.

Heritage Daily said that during a recent survey in Tuan Duong city, archaeologists delineated three ancient cinnabar mines: Thach Mieu Cau, Xuyen Duong Binh and Quoc Gia Loan.

The Shi Mieu Cau mine is located near the Thanh Dong Cau cinnabar mining area in Tuan Duong while the Xuyen Duong Binh and Quoc Gia Loan mines are located along transportation routes, only about 100 km from the tomb. It is likely that this is the source of most of the mercury to create the circulating river system inside Qin Shi Huang’s tomb, matching the description of historian Sima Qian in the book History.

Cinnabar (natural mercury sulfide mineral) is the main material that ancient people used to refine mercury. To extract mercury, simply heat cinnabar in air. The process of converting sulfur to sulfur dioxide also releases pure water in the form of condensable vapor.

Qin Shi Huang’s mausoleum is one of China’s most important archaeological sites, built after he unified his vassal states in 221 BC. In an interview with CCTV in 2024, Wu Yongqi, honorary director of the Qin Shi Huang Tomb Museum, said that underground antiquities should not be disturbed unless excavation is needed to protect them. He warned that artifacts made from plant and animal fibers can degrade immediately after exposure to the outside environment if the tomb is opened without adequate preparation.