The famous terracotta warriors are only a part of the gigantic mausoleum of Qin Shi Huang, the first emperor of unified China, who reigned between 221 and 210 BC.
In fact, the complex, located 30 kilometers east of Xian in the northwest of the country, houses more than 400 tombs covering the impressive area of 60 square kilometers. More than half a million workers worked there for 38 years, following a detailed plan to replicate the entire known China.
The main chamber, where the emperor’s tomb is, has never been opened. The Chinese government, on the recommendation of archeologists working on the site, does not allow it to be opened and examined until they have the technology to safely prevent whatever is inside from being damaged. It may take years, decades or centuries for that to happen.
But then, how do we know what’s inside the tomb? The answer is called Sima Qian. The so-called father of Chinese historiography lived between 145 and 86 B.C. and wrote a general history of the kingdom covering more than 2,000 years in retrospect from his own time.
Known as Shiji (Historical Records), it had been started by his father Sima Tan, and Qian completed it in 91 BC, about five years before his death. It tells the story of the construction of the great mausoleum, the burial of the terracotta warriors and provides concise data, such as the number of 700,000 workers involved in the colossal work.
When his writings were examined by Western historians they were taken with much scepticism, as exaggerations and even mythical legends without historical basis. This was partly justified because Qian often presents legendary and even mythological figures from China’s history as historical facts, assigning them precise chronologies.
However, archaeological discoveries in recent decades have confirmed many of the Shiji’s claims, such as the terracotta warriors and the location of other rulers’ graves. So Qian’s claims are taken very cautiously today, hence the reluctance to open Qin Shi Huang’s tomb.
Because no one knows exactly what’s inside, but Sima Qian says that in the great underground palace, which is larger than a football field, there is a reproduction on a scale of China as known at the time. Including over a hundred rivers, lakes and seas. A kind of microcosm where large amounts of mercury would have been used instead of water to simulate the flow of rivers.
Is it possible that Sima Qian is right about this too? In the 1980s, researchers at China’s Institute of Geophysical and Geochemical Exploration found that the soil surrounding the tomb contains considerably higher concentrations of mercury than the rest of the region. While in remote locations the soils contained an average of 30ppb (parts per billion) of mercury, the average over the vault was 250ppb, and in some sites it was as high as 1500ppb. Some of the archaeologists working at the site believe that this is a very feasible possibility.
Especially when the last tests carried out to measure soil resistivity revealed an intriguing feature of the terrain. A phase anomaly that occurs when an electrical current is reflected by a conductive surface, such as metal.
In addition, analysis of the distribution of mercury levels revealed that it was highest in the northeast, and then in the south, while the northwest corner had very low levels. Overlaying this distribution on a map of China curiously coincides with the location of China’s two great rivers, the Yellow and the Yangtze, seen from the ancient capital Qin, about 30 kilometers from the monument.
According to Yinglan Zhang, who led the excavations from 1998 to 2007, there should be many other cultural artifacts and relics buried in the main chamber and in other tombs around it, possibly things that are beyond our imagination. But he also believes that the distribution of mercury may not be a reliable indicator. The chamber may have collapsed thousands of years ago, just as the graves containing the terracotta army did. The mercury may have volatilized and drained through the soil for centuries.
It should be noted that the terracotta warriors were found outside the 2 km wall surrounding the main chamber. Inside the wall were found buildings that contained food and other objects that the emperor might need in the afterlife. It is also possible that the emperor was not buried alone. Sima Qian claims that many officers were buried with him, although it is not clear whether they were alive or dead at the time. Many of these buildings and objects could have been gilded using gold and silver diluted in mercury as a pigment, a common practice at the time.
If it were the case that the mercury detected had been used for these decorative purposes, specialists doubt that there would be a large quantity. Based on estimates of mercury production in the Song era, they believe that at most we would be talking about around 100 tonnes, approximately 7 cubic metres. We may never know the secrets of the tomb of Emperor Qin Shi Huang.
Sources: Chemistry World / Science and Civilisation in China (Joseph Needham) / Chinese refuse to open the mysterious tomb of their first emperor and the remaining 6,000 terracotta soldiers / The Secret Tomb of China’s 1st Emperor: Will We Ever See Inside? / Wikipedia