The Terracotta Warriors and Horses within the mausoleum of Qin Shihuang, the first emperor of a united China, was one of the main reasons why Y.W Kengqelova made her trip from Russia to China.

Archaeologists will begin a third phase of excavation at the famous terracotta army site on June 13. This is a 200-sq m patch in the north-central part of the No 1 pit, the largest among three pits at the site. [CFP]

She has been in Xi'an in China's northwest for two days, waiting for her chance to see the next chapter of the story unfold.

"I couldn't wait to see them. I heard that there is going to be an excavation (of the terracotta army site) starting on Saturday when visitors are allowed to look on," said the Russian visitor.

"I really don't know what to expect from the excavation - some say there might be colored warriors unearthed if we're lucky - but the experience of witnessing the excavation will be very exciting whatever happens."

Kengqelova is not alone.

Many tourists have timed their visits to the site so they can be there when the dig gets underway Saturday- which is also the fourth World Heritage Day in China.

The excavation into the first and largest of the three pits at the site will continue through - out next year and may not produce immediate discoveries, warned Meng Jianming, dean of the museum's media office.

But experts are hoping for some major finds in the weeks and months to come, said Liu Zhancheng, head of the archeological team at the terracotta museum.

"We're hoping to find a clay figure representing a high-ranking army officer, for example," he told Xinhua.

The museum's website said only 10 figures from the more than 8,000 clay statues unearthed so far have been "armored generals" - and there have been none from No 1 pit.

While surprise discoveries are hoped for from the excavation in a 200-sq-m section of the 14,260-sq-m No 1 pit, the dig is mainly being carried out to test preservation technology that the museum has spent decades developing to ensure terracotta figures remain intact and retain their original colors, said an official surnamed Peng from the Administration of Cultural Heritage.

Challenges in preserving the terracotta warriors after they have been unearthed forced Chinese scientists to scale back excavations in the past.

Researchers said lacquer on the terracotta warriors is highly sensitive to temperature change, and the warriors also suffered from mildew and drying out after they were excavated from the damp earth.

A lack of color-preserving technology stalled the second large-scale excavation in 1985, according to Zhang Zhijun, deputy director of the museum's Protection Department. The first formal excavation of the site lasted for six years from 1978 to 1984 and uncovered 1,087 clay figures.

Since 1990, the museum has been working with experts from Bavaria, Germany, on the protection of colored drawings on the terracotta warriors and horses. So far, scientists have come up with a liquid mixture of polyurethane to preserve the lacquer and have succeeded in protecting several hundred warriors from further decay, said Zhang.

"The upcoming excavation will be a test of the technology," said Zhang, adding that ground water and earthquakes also present challenges.

Air pollution is another major threat, according to Cao Junji, an assistant researcher at the Institute of Earth Environment, a branch of the Chinese Academy of Sciences.

In 2005, Cao warned that the emperor's mausoleum will become a coal mine in 100 years due to severe air pollution, a prediction that the museum said will not happen because of its anti-weathering initiatives.

The terracotta army was accidentally discovered in Lintong county, 35 km east of Xi'an, in 1974 by farmers who were attempting to dig a well, said Peng. The current excavation site is thought to contain about 6,000 life-sized terracotta figures.

(China Daily June 13, 2009)